WO2023007426A1

WO2023007426A1 - Novel styrene compounds and a process for the preparation thereof

Info

Publication number: WO2023007426A1
Application number: PCT/IB2022/056996
Authority: WO
Inventors: Sanjay Maruti MADURKAR; Dipak Jaysing DHAWADE; Vinay Sadashiv KADAM; Pranab Kumar Patra; Alexander Guenther Maria KLAUSENER
Original assignee: Pi Industries Ltd.
Priority date: 2021-07-29
Filing date: 2022-07-28
Publication date: 2023-02-02
Also published as: AR126600A1; TW202313564A

Abstract

The present invention relates to a novel styrene compound of Formula (I) or a salt thereof Formula (I) wherein, the definition of Q, R², and m are as described in the description. The present invention also relates to a process for the preparation of styrene compounds of Formula (I) or a salt thereof.

Description

NOVEL STYRENE COMPOUNDS AND A PROCESS FOR THE PREPARATION THEREOF FIELD OF THE INVENTION The present invention relates to a novel styrene of formula (I) or a salt thereof. The invention further relates to a process for the preparation of a novel styrene of formula (I) or a salt thereof. Particularly, the present invention relates to compounds of formula (IA) and (IB) or a salt thereof and a process for the preparation thereof. More particularly, the present invention relates to compounds of formula (IA- a) and (IB-a) or a salt thereof and a process for the preparation thereof. BACKGROUND OF THE INVENTION It is known from the prior art, for example, from WO2008013925, WO2012020060, WO2016024434, WO2019048988 and WO2019048989 describes thiazolyl-piperidinyl heterocyclic compounds can be used as fungicidal crop protection agents. WO2021094904 describes phenyl sulfilimines or sulfoximines containing thiazolyl-piperidinyl compounds having an improved fungicidal activity. Substituted styrene compounds are key fragments in the preparation of above mentioned phenyl sulfilimines or sulfoximines containing thiazolyl-piperidinyl compounds. Various prior arts report the synthesis of substituted styrenes, for example, Organic Syntheses (1948), 28, 31-3; Tetrahedron (2010), 66(5), 1102-1110; WO2018193387 and WO2016139161. However, styrene compounds that are substituted with sulfilimine or sulfoximine functional groups are not reported in the prior art. There is an unmet need to find a simple, efficient, and industrially economical process for the preparation of novel styrene compounds. Accordingly, the present invention provides a simple, environment-friendly, and cost-effective process for the preparation of sulfilimine or sulfoximine substituted styrene compounds, based on easily accessible starting materials. OBJECTIVE OF THE INVENTION One of the main objectives of the present invention is to provide a novel styrene compound of formula (I) or a salt thereof, which is useful as an intermediate in the preparation of phenyl sulfilimines or sulfoximines containing thiazolyl-piperidinyl based chemical pesticides. Another objective of the present invention is to provide a simple, environmentally friendly and cost- effective process for the preparation of a styrene compound of formula (I) or a salt thereof, based on easily available starting materials. In one embodiment, the present invention provides a process for the preparation of N-linked sulfilimine/sulfoximine substituted styrene compounds of formula (IA) or a salt thereof. In another embodiment, the present invention provides a process for the preparation of S-linked sulfilimine/sulfoximine substituted styrene compounds of formula (IB) or a salt thereof. SUMMARY OF THE INVENTION Accordingly, the present invention provides a novel styrene of formula (I) or a salt thereof

Formula (I) wherein, R² is selected from the group consisting of halogen, cyano, hydroxy, C₁-C₆-alkyl, C₁-C₆-alkoxy, C₁-C₆-alkylthio, C₁-C₆-haloalkyl, C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl, C₁-C₆-alkylsulfinyl, and C₁-C₆-alkylsulfonyl; m is an integer selected from 0 to 3; Q is selected from -N=S(=O)_0-1(R⁶)(R⁷) or -S(=O)_0-1(R⁵)(=NR⁴); R⁴ is selected from the group consisting of hydrogen, cyano, hydroxy, C₁-C₆-alkyl, C₃-C₆- cycloalkyl, C₃-C₆-cycloalkyl-C₁-C₆alkyl, C₁-C₆-alkylcarbonyl and C₁-C₆-haloalkyl carbonyl; R⁵ and R⁶ are independently selected from the group consisting of C₁-C₆-alkyl, C₂-C₆-alkenyl, C₃-C₆-cycloalkyl, C₃-C₆-cycloalkyl-C₁-C₆alkyl, C₁-C₆-haloalkyl, C₃-C₆-halocycloalkyl and phenyl; R⁷ is independently selected from the group consisting of C₁-C₆-alkyl, C₂-C₆-alkenyl, C₃-C₆- cycloalkyl, C₃-C₆-cycloalkyl-C₁-C₆alkyl, C₁-C₆-haloalkyl and C₃-C₆-halocycloalkyl; R⁴ or R⁵ with the C atom contiguous to the C atom substituted with Q may form a 4- to 6- membered heterocyclic ring, wherein the C atoms of the heterocyclic ring may be optionally replaced by C(=O) or C(=S); R⁶ and R⁷ together with the (S) atom to which they are attached may form a 4- to 6- membered heterocyclic ring, wherein the C atoms of the heterocyclic ring may be optionally replaced by C(=O) or C(=S); or R⁴ or R⁵ or R⁶ with R² may form a 4- to 6- membered heterocyclic ring, wherein the C atoms of the heterocyclic ring may be optionally replaced by C(=O) or C(=S); or R⁶ or R⁷ with the C atom contiguous to the C atom substituted with Q may form a 4- to 6- membered heterocyclic ring, wherein the C atoms of the heterocyclic ring may be optionally replaced by C(=O) or C(=S); wherein, said heterocyclic rings may be optionally substituted with the group consisting of halogen, cyano, C₁-C₆-alkyl, C₃-C₆-cycloalkyl, C₁-C₆-haloalkyl or C₃-C₆-halocycloalkyl; or salts, metal complexes, stereoisomers, and polymorphs thereof; excluding the compound 6-fluoro-2-methyl-7-vinyl-3H-2λ⁴-benzo[c]isothiazole-2-oxide. In another embodiment, the present invention provides a process for preparing a novel styrene of formula (I) or a salt thereof

Formula (I) wherein, Q, R² and m are as defined above; comprising the step of, converting a compound of formula (IV) or a salt thereof to the compound of formula (I) or a salt thereof, in the presence of a suitable reagent and a suitable solvent as shown in the scheme below:

wherein, X represents halogen or a suitable leaving group; Q, R² and m are as defined above. In one embodiment, the present invention provides a novel styrene of formula (IA) and (IB) or a salt thereof; wherein, Q represents -N=S(=O)_0-1(R⁶)(R⁷) or -S(=O)_0-1(R⁵)(=NR⁴)

wherein, R², R⁴, R⁵, R⁶, R⁷ and m are as defined above. In a preferred embodiment, the present invention provides a novel styrene of formula (IA-a) or a salt thereof and (IB-a) or a salt thereof. wherein, R², R⁴, R⁵, R⁶ and R⁷ are as defined above. In yet another embodiment, the present invention provides a process for preparing N-substituted sulfilimine/sulfoximine substituted styrene of formula (IA) or a salt thereof. In still another embodiment, the present invention provides a process for preparing S-substituted sulfilimine/sulfoximine substituted styrene of formula (IB) or a salt thereof. DETAILED DESCRIPTION OF THE INVENTION: The definitions provided herein for the terminologies used in the present disclosure are for illustrative purpose only and in no manner limit the scope of the present invention disclosed in the present disclosure. As used herein, the terms “comprises”, “comprising”, “includes”, “including”, “has”, “having”, “contains”, “containing”, “characterized by” or any other variation thereof, are intended to cover a non- exclusive inclusion, subject to any limitation explicitly indicated. For example, a composition, mixture, process or method that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, mixture, process or method. The transitional phrase “consisting of” excludes any element, step or ingredient not specified. If in the claim, such would close the claim to the inclusion of materials other than those recited except for impurities ordinarily associated therewith. When the phrase “consisting of” appears in a clause of the body of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole. The transitional phrase “consisting essentially of” is used to define a composition or method that includes materials, steps, features, components or elements, in addition to those literally disclosed, provided that these additional materials, steps, features, components or elements do not materially affect the basic and novel characteristic(s) of the claimed invention. The term “consisting essentially of” occupies a middle ground between “comprising” and “consisting of”. Further, unless expressly stated to the contrary, “or” refers to an inclusive “or” and not to an exclusive “or”. For example, a condition A “or” B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B is true (or present). Also, the indefinite articles “a” and “an” preceding an element or component of the present invention are intended to be non-restrictive regarding the number of instances (i.e. occurrences) of the element or component. Therefore “a” or “an” should be read to include one or at least one, and the singular word form of the element or component also includes the plural unless the number is obviously meant to be singular. Carbon-based radical refers to a monovalent molecular component comprising a carbon atom that connects the radical to the remainder of the chemical structure through a single bond. Carbon-based radicals can optionally comprise saturated, unsaturated and aromatic groups, chains, rings and ring systems, and heteroatoms. Although carbon-based radicals are not subject to any particular limit in size, in the context of the present invention they typically comprise 1 to 16 carbon atoms and o to 3 heteroatoms. Of note are carbon-based radicals selected from C₁-C₆-alkyl, C₁- C₆-haloalkyl and phenyl optionally substituted with 1-3 substituents selected from C₁-C₃ alkyl, halogen and nitro. The meaning of various terms used in the description shall now be illustrated. The term “alkyl”, used either alone or in compound words such as “alkylthio” or “haloalkyl” or - N(alkyl) or alkylcarbonylalkyl or alkylsuphonylamino includes straight-chain or branched C₁ to C₁₂ alkyl, preferably C₁ to C₆ alkyl. Representative examples of alkyl include but not limited to methyl, ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, pentyl, 1- methylbutyl, 2-methylbutyl, 3-methylbutyl, 2,2-dimethylpropyl, 1-ethylpropyl, hexyl, 1,1- dimethylpropyl, 1,2-dimethylpropyl, or the different isomers. If the alkyl is at the end of a composite substituent, as, for example, in alkylcycloalkyl, the part of the composite substituent at the start, for example the cycloalkyl, may be mono- or polysubstituted identically or differently and independently by alkyl. The same also applies to composite substituents in which other radicals, for example alkenyl, alkynyl, hydroxyl, halogen, carbonyl, carbonyloxy and the like, are at the end. The term “alkenyl”, used either alone or in compound words includes straight-chain or branched C₂ to C₁₂ alkenes, preferably C₂ to C₆, alkenes. Non-limiting examples of alkenes include ethenyl, 1-propenyl, 2-propenyl, 1-methylethenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-methyl- 1-propenyl, 2-methyl- 1- propenyl, 1-methyl-2-propenyl, 2-methyl-2-propenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, 1-methyl-1-butenyl, 2-methyl-1-butenyl, 3-methy1-1-butenyl, 1-methy1-2-butenyl, 2-methyl-2-butenyl, 3-methyl-2-butenyl, 1-methyl-3-butenyl, 2-methyl-3-butenyl, 3-methyl-3-butenyl, 1,1-dimethyl-2- propenyl, 1,2-dimethyl-1-propenyl, 1,2-dimethyl-2-propenyl, 1-ethyl-1-propenyl, l-ethyl-2-propenyl, 1- hexenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl, 5-hexenyl, 1-methyl-1-pentenyl, 2-methyl-1-pentenyl, 3- methyl-1-pentenyl, 4-methyl-1-pentenyl, 1-methyl-2-pentenyl, 2-methyl-2-pentenyl, 3-methyl-2- pentenyl, 4-methyl-2-pentenyl, 1-methyl-3-pentenyl, 2-methyl-3-pentenyl, 3-methyl-3-pentenyl, 4- methyl-3-pentenyl, 1-methyl-4-pentenyl, 2-methyl-4-pentenyl, 3-methyl-4-pentenyl, 4-methyl-4- pentenyl, 1,1-dimethyl-2-butenyl, 1,1-dimethyl-3-butenyl, 1,2-dimethyl-lbutenyl, 1,2-dimethyl-2- butenyl, 1,2-dimethyl-3-butenyl, 1,3-dimethyl-1-butenyl, 1,3-dimethyl-2-butenyl, 1,3-dimethyl-3- butenyl, 2,2-dimethy1-3-butenyl, 2,3-dimethyl-1-butenyl, 2,3-dimethyl-2-butenyl, 2,3-dimethyl-3- butenyl, 3,3-dimethyl-1-butenyl, 3,3-dimethyl-2-butenyl, 1-ethyl-1-butenyl, 1-ethyl-2-butenyl, 1-ethyl- 3-butenyl, 2-ethyl-1-butenyl, 2-ethyl-2-butenyl, 2-ethyl-3-butenyl, 1,1,2-trimethyl-2-propenyl, 1-ethyl- 1-methyl-2-propenyl, 1-ethyl-2-methyl-1-propenyl and 1-ethyl-2-methyl-2-propenyl and the different isomers. “Alkenyl” also includes polyenes such as 1,2-propadienyl and 2,4-hexadienyl. This definition also applies to alkenyl as a part of a composite substituent, for example haloalkenyl and the like, unless defined specifically elsewhere. The term “alkynyl”, used either alone or in compound words includes straight-chain or branched C₂ to C₁₂ alkynes, preferably C₂ to C₆, alkynes. Non-limiting examples of alkynes include ethynyl, 1- propynyl, 2-propynyl, 1-butynyl, 2-butynyl, 3-butynyl, 1-methyl-2-propynyl, 1-pentynyl, 2-pentynyl, 3- pentynyl, 4-pentynyl, 1-methyl-2-butynyl, 1-methyl-3-butynyl, 2-methyl-3-butynyl, 3-methyl-1- butynyl, 1,1 -dimethyl-2-propynyl, 1-ethyl -2-propynyl, 1-hexynyl, 2-hexynyl, 3-hexynyl, 4-hexynyl, 5-hexynyl, 1-methyl-2-pentynyl, 1-methyl-3-pentynyl, 1-methyl-4-pentynyl, 2-methyl-3-pentynyl, 2- methyl-4-pentynyl, 3-methyl-1-pentynyl, 3-methyl-4-pentynyl, 4-methyl-1-pentynyl, 4-methyl-2- pentynyl, 1,1 -dimethyl-2-butynyl, l,l-dimethyl-3-butynyl, 1,2-dimethyl-3-butynyl, 2,2-dimethyl-3- butynyl, 3,3-dimethyl-1-butynyl, l-ethyl-2-butynyl, l-ethyl-3-butynyl, 2-ethyl-3-butynyl and 1-ethyl-1- methyl-2-propynyl and the different isomers. This definition also applies to alkynyl as a part of a composite substituent, for example haloalkynyl etc., unless specifically defined elsewhere. “Alkynyl” can also include moieties comprised of multiple triple bonds such as 2,5-hexadiynyl. The term "cycloalkyl" means alkyl closed to form a ring. Non-limiting examples include but are not limited to cyclopropyl, cyclopentyl and cyclohexyl. This definition also applies to cycloalkyl as a part of a composite substituent, for example cycloalkylalkyl etc., unless specifically defined elsewhere. The term “cycloalkylalkyl” means cycloalkyl substituent on alkyl, for example, cyclopropyl or cyclobutyl or cyclopentyl are substituted on any carbon of C₁-C₆ alkyl. Representative examples of cycloalkylalkyl include cyclopropyl methyl, cyclopropyl ethyl. The term “alkoxy” includes C1 to C₆ alkoxy. Examples of alkoxy include methoxy, ethoxy, propoxy, 1- methylethoxy, butoxy, 1-methylpropoxy, 2-methylpropoxy, 1,1-dimethylethoxy, pentoxy, 1- methylbutoxy, 2-methylbutoxy, 3-methylbutoxy, 2,2-dimethylpropoxy, 1-ethylpropoxy, hexoxy, 1,1- dimethylpropoxy, 1,2-dimethylpropoxy, 1-methylpentoxy, 2-methylpentoxy, 3-methylpentoxy, 4- methylpentoxy, 1,1-dimethylbutoxy, 1,2-dimethylbutoxy, 1,3-dimethylbutoxy, 2,2-dimethylbutoxy, 2,3-dimethylbutoxy, 3,3-dimethylbutoxy, 1-ethylbutoxy, 2-ethylbutoxy, 1,1,2-trimethylpropoxy, 1,2,2- trimethylpropoxy, 1-ethyl-1-methylpropoxy and 1-ethyl-2-methylpropoxy and the different isomers. This definition also applies to alkoxy as a part of a composite substituent, for example haloalkoxy, alkynylalkoxy, etc., unless specifically defined elsewhere. The term "Alkoxyalkyl" denotes alkoxy substitution on alkyl. Non-limiting examples of "alkoxyalkyl" include CH₃OCH₂, CH₃OCH₂CH₂, CH₃CH₂OCH₂, CH₃CH₂CH₂CH₂OCH₂ and CH₃CH₂OCH₂CH₂. The term “alkylthio” used either alone or in compound words included C₁ to C₁₂ alkylthio, most preferably C₁ to C₆ alkylthio. The term “alkylthio” includes branched or straight-chain alkylthio ("-S- alkyl") moieties such as methylthio, ethylthio, propylthio, 1-methylethylthio, butylthio, 1- methylpropylthio, 2-methylpropylthio, 1,1-dimethylethylthio, pentylthio, 1-methylbutylthio, 2- methylbutylthio, 3-methylbutylthio, 2,2-dimethylpropylthio, 1-ethylpropylthio, hexylthio, 1,1- dimethylpropylthio, 1,2-dimethylpropylthio, 1-methylpentylthio, 2-methylpentylthio, 3- methylpentylthio, 4-methylpentylthio, 1,1-dimethylbutylthio, 1,2-dimethylbutylthio,1,3- dimethylbutylthio, 2,2-dimethylbutylthio, 2,3-dimethylbutylthio, 3,3-dimethylbutylthio, 1- ethylbutylthio, 2-ethylbutylthio, 1,1,2-trimethylpropylthio, 1,2,2-trimethylpropylthio, 1-ethyl- 1- methylpropylthio and 1-ethyl-2-methylpropylthio and the different isomers Suitable examples of "alkylsulfinyl" or "-S(O)-alkyl" include but are not limited to methylsulphinyl, ethylsulphinyl, propylsulphinyl, 1-methylethylsulphinyl, butylsulphinyl, 1-methylpropylsulphinyl, 2- methylpropylsulphinyl, 1,1-dimethylethylsulphinyl, pentylsulphinyl, 1-methylbutylsulphinyl, 2- methylbutylsulphinyl, 3-methylbutylsulphinyl, 2,2-dimethylpropylsulphinyl, 1-ethylpropylsulphinyl, hexylsulphinyl, 1,1-dimethylpropylsulphinyl, 1,2-dimethylpropylsulphinyl, 1-methylpentylsulphinyl, 2-methylpentylsulphinyl, 3-methylpentylsulphinyl, 4-methylpentylsulphinyl, 1,1- dimethylbutylsulphinyl, 1,2-dimethylbutylsulphinyl, 1,3-dimethylbutylsulphinyl, 2,2- dimethylbutylsulphinyl, 2,3-dimethylbutylsulphinyl, 3,3-dimethylbutylsulphinyl, 1- ethylbutylsulphinyl, 2-ethylbutylsulphinyl, 1,1,2-trimethylpropylsulphinyl, 1,2,2- trimethylpropylsulphinyl, 1-ethyl-1-methylpropylsulphinyl and 1-ethyl-2-methylpropylsulphinyl and the different isomers. The term "arylsulfinyl" includes Ar-S(O), wherein Ar can be any carbocyle or heterocylcle. This definition also applies to alkylsulphinyl as a part of a composite substituent, for example haloalkylsulphinyl etc., unless specifically defined elsewhere. Suitable examples of "alkylsulfonyl" or "-S(O)2-alkyl" include but are not limited to methylsulphonyl, ethylsulphonyl, propylsulphonyl, 1-methylethylsulphonyl, butylsulphonyl, 1-methylpropylsulphonyl, 2-methylpropylsulphonyl, 1,1-dimethylethylsulphonyl, pentylsulphonyl, 1-methylbutylsulphonyl, 2- methylbutylsulphonyl, 3-methylbutylsulphonyl, 2,2-dimethylpropylsulphonyl, 1- ethylpropylsulphonyl, hexylsulphonyl, 1,1-dimethylpropylsulphonyl, 1,2-dimethylpropylsulphonyl, 1- methylpentylsulphonyl, 2-methylpentylsulphonyl, 3-methylpentylsulphonyl, 4-methylpentylsulphonyl, 1,1-dimethylbutylsulphonyl, 1,2-dimethylbutylsulphonyl, 1,3-dimethylbutylsulphonyl, 2,2- dimethylbutylsulphonyl, 2,3-dimethylbutylsulphonyl, 3,3-dimethylbutylsulphonyl, 1- ethylbutylsulphonyl, 2-ethylbutylsulphonyl, 1,1,2-trimethylpropylsulphonyl, 1,2,2- trimethylpropylsulphonyl, 1-ethyl-1-methylpropylsulphonyl and 1- ethyl-2-methylpropylsulphonyl and the different isomers. The term "arylsulfonyl" includes Ar-S(O)₂, wherein Ar can be any carbocyle or heterocylcle. This definition also applies to alkylsulphonyl as a part of a composite substituent, for example alkylsulphonylalkyl etc., unless defined elsewhere. The term hydroxy means –OH, amino means–NRR, wherein R can be H or any possible substituent such as alkyl. Carbonyl means -C(O)- , carbonyloxy means -OC(O)-, sulfinyl means SO, sulfonyl means S(O)₂. The term “halogen”, either alone or in compound words such as “haloalkyl”, includes fluorine, chlorine, bromine or iodine. Further, when used in compound words such as “haloalkyl”, said alkyl may be partially or fully substituted with halogen atoms which may be the same or different. Non-limiting examples of “haloalkyl” include chloromethyl, bromomethyl, dichloromethyl, trichloromethyl, fluoromethyl, difluoromethyl, trifluoromethyl, chlorofluoromethyl, dichlorofluoromethyl, chlorodifluoromethyl, 1-chloroethyl, 1-bromoethyl, 1-fluoroethyl, 2-fluoroethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, 2-chloro-2-fluoroethyl, 2-chloro-2,2-difluoroethyl, 2,2-dichloro-2-fluoroethyl, 2,2,2-trichloroethyl, pentafluoroethyl, 1,1-dichloro-2,2,2-trifluoroethyl, and 1,1,1-trifluoroprop-2-yl. This definition also applies to haloalkyl as a part of a composite substituent, for example haloalkylaminoalkyl etc., unless specifically defined elsewhere. The terms “haloalkenyl” and “haloalkynyl” are defined analogously except that, instead of alkyl groups, alkenyl and alkynyl groups are present as a part of the substituent. The term “haloalkoxy” means straight-chain or branched alkoxy groups where some or all of the hydrogen atoms in these groups may be replaced by halogen atoms as specified above. Non-limiting examples of haloalkoxy include chloromethoxy, bromomethoxy, dichloromethoxy, trichloromethoxy, fluoromethoxy, difluoromethoxy, trifluoromethoxy, chlorofluoromethoxy, dichlorofluoromethoxy, chlorodifluoromethoxy, 1-chloroethoxy, 1-bromoethoxy, 1-fluoroethoxy, 2-fluoroethoxy, 2,2- difluoroethoxy, 2,2,2-trifluoroethoxy, 2-chloro-2-fluoroethoxy, 2-chloro-2,2-difluoroethoxy, 2,2- dichloro-2-fluoroethoxy, 2,2,2-trichloroethoxy, pentafluoroethoxy and l,l,l-trifluoroprop-2-oxy. This definition also applies to haloalkoxy as a part of a composite substituent, for example haloalkoxyalkyl etc., unless specifically defined elsewhere. The terms “haloalkylthio” or “haloalkylsulfanyl” means straight-chain or branched alkylthio groups where some or all of the hydrogen atoms in these groups may be replaced by halogen atoms as specified above. Non-limiting examples of haloalkylthio include chloromethylthio, bromomethylthio, dichloromethylthio, trichloromethylthio, fluoromethylthio, difluoromethylthio, trifluoromethylthio, chlorofluoromethylthio, dichlorofluoromethylthio, chlorodifluoromethylthio, 1-chloroethylthio, 1- bromoethylthio, 1- fluoroethylthio, 2-fluoroethylthio, 2,2-difluoroethylthio, 2,2,2-trifluoroethylthio, 2- chloro-2- fluoroethylthio, 2-chloro-2,2-difluoroethylthio, 2,2-dichloro-2-fluoroethylthio, 2,2,2- trichloroethylthio, pentafluoroethylthio and 1,1,1-trifluoroprop-2-ylthio. This definition also applies to haloalkylthio as a part of a composite substituent, for example haloalkylthioalkyl etc., unless specifically defined elsewhere. Non limiting examples of “haloalkylsulfinyl” include CF₃S(O), CCl₃S(O), CF₃CH₂S(O) and CF₃CF₂S(O). Non limiting examples of “haloalkylsulfonyl” include CF₃S(O)₂, CCl₃S(O)₂, CF₃CH₂S(O)₂ and CF₃CF₂S(O)₂. Halocycloalkyl, halocycloalkenyl, alkylcycloalkyl, cycloalkoxyalkyl, alkylsulfinylalkyl, alkylsulfonylalkyl, haloalkylcarbonyl, cycloalkylcarbonyl, haloalkoxylalkyl, and the like, are defined analogously to the above examples. The term “hydroxy” means –OH, “amino” means –NRR, wherein R can be H or any possible substituent such as alkyl; “carbonyl” means -C(O)- , “carbonyloxy” means -OC(O)-, “sulfinyl” means SO, “sulfonyl” means S(O)2. The term “alkylcarbonyl” is an alkyl group bonded to a skeleton via a carbonyl group (-CO-). This definition also applies to alkylcarbonyl as a part of composite substituent, for example, cycloalkylalkylcarbonyl and the like, unless specifically defined elsewhere. Non-limiting examples of "alkylcarbonyl" include C(O)CH₃, C(O)CH₂CH₂CH₃ and C(O)CH(CH₃)2. Cycloalkylcarbonyl, and the like, are defined analogously to the above examples. The term “amide” means A-R'C=ONR''-B, wherein R' and R'' indicates substituents and A and B indicate any group. The term “thioamide” means A-R'C=SNR''-B, wherein R' and R'' indicates substituents and A and B indicate any group. The term "heterocycle" or "heterocyclic" or "heterocyclic ring system" includes "aromatic heterocycle" or "heteroaryl bicyclic ring system" and "nonaromatic heterocycle ring system" or polycyclic or bicyclic (spiro, fused, bridged, non-fused) ring compounds in which ring may be aromatic or non-aromatic, wherein the heterocycle ring contains at least one heteroatom selected from N, O, S(O)0-2, and or C ring 10 member of the heterocycle may be replaced by C(=O), C(=S), C(=CR*R*) and C=NR*, * indicates integers. The term "non-aromatic heterocycle" or "non-aromatic heterocyclic" means three- to fifteen-membered, preferably three- to twelve-membered, saturated or partially unsaturated heterocycle containing one to four heteroatoms from the group of oxygen, nitrogen and sulphur: mono, bi- or tricyclic heterocycles 15 which contain, in addition to carbon ring members, one to three nitrogen atoms and/or one oxygen or sulphur atom or one or two oxygen and/or sulphur atoms; if the ring contains more than one oxygen atom, they are not directly adjacent; for example (but not limited to) oxiranyl, aziridinyl, oxetanyl, azetidinyl, thietanyl, tetrahydrofuranyl, tetrahydrothienyl, pyrrolidinyl, isoxazolidinyl, isothiazolidinyl, pyrazolidinyl, oxazolidinyl, thiazolidinyl, imidazolidinyl, 1,2,4-oxadiazolidinyl, 1,2,4-thiadiazolidinyl, 1,2,4-triazolidin-1-yl, 1,2,4-triazolidin-3-yl, 1,2,3-triazolidinyl, 1,2,3-oxadiazolidinyl, 1,3,4- thiadiazolidinyl, 1,3,4-triazolidinyl, dihydrofuryl, dihydrothienyl, pyrrolinyl, isoxazolinyl, isothiazolinyl, dihydropyrazolyl, dihydrooxazolyl, dihydrothiazolyl,piperidinyl, pyrazynyl, morpholinyl, thiomorphlinyl, 1,3-dioxan-5-yl, tetrahydropyranyl, tetrahydrothienyl, hexahydropyridazinyl, hexahydropyrimidinyl, piperazinyl and cycloserines. This definition also applies to heterocyclyl as a part of a composite substituent, for example heterocyclylalkyl etc., unless specifically defined elsewhere. As used herein, the term “suitable leaving group” refers to a molecular fragment that departs with a pair of electrons in heterolytic bond cleavage. Non-limiting examples of suitable leaving groups include halo groups selected from chloro, iodo, or bromo, aryl or alkyl sulfonates such as tosylate (p- toluenesulfonate), triflate (trifluoromethanesulfonate), nosylate or mesylate (methanesulfonate) and the like. As used herein, the term “reacting” or “treating” refers to the act of “mixing”, “intermixing” or “putting together” for the purposes of bringing two or more chemical compounds in close contact so as to promote a chemical reaction. For example, certain substrates, reagents or ingredients, reagents as described in the summary of the invention are “combined” with each other in an appropriate vessel, container or apparatus in such a fashion that the substrates, reagents or ingredients can chemically react with one another so that a new product can be formed. The total number of carbon atoms in a substituent group is indicated by the "Ci-Cj" prefix where i and j are numbers from 1 to 21. For example, C₁-C₃ alkylsulfonyl designates methylsulfonyl through propylsulfonyl; C₂ alkoxyalkyl designates CH₃OCH₂; C₃ alkoxyalkyl designates, for example, CH₃CH(OCH₃), CH₃OCH₂CH₂ or CH₃CH₂OCH₂; and C₄ alkoxyalkyl designates the various isomers of an alkyl group substituted with an alkoxy group containing a total of four carbon atoms, examples including CH₃CH₂CH₂OCH₂ and CH₃CH₂OCH₂CH₂. In the above recitations, when a compound of formula (I) is comprised of one or more heterocyclic rings, all substituents are attached to these rings through any available carbon or nitrogen by replacement of a hydrogen on said carbon or nitrogen. When a compound is substituted with a substituent bearing a subscript that indicates the number of said substituents can exceed 1, said substituents (when they exceed 1) are independently selected from the group of defined substituents. Further, when the subscript m in (R)m indicates an integer ranging from for example, 0 to 4 then the number of substituents may be selected from the integers between 0 and 4 inclusive. When a group contains a substituent which can be hydrogen, then, when this substituent is taken as hydrogen, it is recognized that said group is being un-substituted. The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skilled in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein. The description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein. Any discussion of documents, acts, materials, devices, articles and the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application. The numerical values mentioned in the description and the description/claims though might form a critical part of the present invention of the present invention, any deviation from such numerical values shall still fall within the scope of the present invention if that deviation follows the same scientific principle as that of the present invention disclosed in the present invention. The inventive compound of the present invention may, if appropriate, be present as mixtures of different possible isomeric forms, especially of stereoisomers, for example E and Z, threo and erythro, and also optical isomers, but if appropriate also of tautomers. Both the E and the Z isomers, and also the threo and erythro isomers, and the optical isomers, any desired mixtures of these isomers and the possible tautomeric forms are disclosed and claimed. The invention is described below in detail, in connection with certain preferred and optional embodiments of the present invention, so that various aspects thereof could be fully understood and appreciated. In one particular embodiment, the present invention provides a novel styrene of formula (I) or a salt thereof Formula (I) wherein, R² is selected from the group consisting of halogen, cyano, hydroxy, C₁-C₆-alkyl, C₁-C₆-alkoxy, C₁-C₆-alkylthio, C₁-C₆-haloalkyl, C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl, C₁-C₆-alkylsulfinyl, and C₁-C₆-alkylsulfonyl; m is an integer selected from 0 to 3; Q is selected from -N=S(=O)_0-1(R⁶)(R⁷) or -S(=O)_0-1(R⁵)(=NR⁴); R⁴ is selected from the group consisting of hydrogen, cyano, hydroxy, C₁-C₆-alkyl, C₃-C₆- cycloalkyl, C₃-C₆-cycloalkyl-C₁-C₆alkyl, C₁-C₆-alkylcarbonyl and C₁-C₆-haloalkyl carbonyl; R⁵ and R⁶ are independently selected from the group consisting of C₁-C₆-alkyl, C₂-C₆-alkenyl, C₃-C₆-cycloalkyl, C₃-C₆-cycloalkyl-C₁-C₆alkyl, C₁-C₆-haloalkyl, C₃-C₆-halocycloalkyl and phenyl; R⁷ is independently selected from the group consisting of C₁-C₆-alkyl, C₂-C₆-alkenyl, C₃-C₆- cycloalkyl, C₃-C₆-cycloalkyl-C₁-C₆alkyl, C₁-C₆-haloalkyl and C₃-C₆-halocycloalkyl; R⁴ or R⁵ with the C atom contiguous to the C atom substituted with Q may form a 4- to 6- membered heterocyclic ring, wherein the C atoms of the heterocyclic ring may be optionally replaced by C(=O) or C(=S); R⁶ and R⁷ together with the S atom to which they are attached may form a 4- to 6- membered heterocyclic ring, wherein the C atoms of the heterocyclic ring may be optionally replaced by C(=O) or C(=S); or R⁴ or R⁵ or R⁶ with the R² may form a 4- to 6- membered heterocyclic ring, wherein the C atoms of the heterocyclic ring may be optionally replaced by C(=O) or C(=S); or R⁶ or R⁷ with the C atom contiguous to the C atom substituted with Q may form a 4- to 6- membered heterocyclic ring, wherein the C atoms of the heterocyclic ring may be optionally replaced by C(=O) or C(=S); wherein, said heterocyclic rings may be optionally substituted with the group consisting of halogen, cyano, C₁-C₆-alkyl, C₃-C₆-cycloalkyl, C₁-C₆-haloalkyl or C₃-C₆- halocycloalkyl; or salts, metal complexes, isomers, and polymorphs thereof; excluding the compound 6-fluoro-2-methyl-7-vinyl-3H-2λ⁴-benzo[c]isothiazole-2-oxide. In another embodiment, the present invention provides a process for preparing a styrene of formula (I) or a salt thereof, Formula (I) wherein, Q, R² and m are as defined above; comprising the step of: converting a compound of formula (IV) or a salt thereof, to a compound of formula (I) or a salt thereof, in the presence of a suitable reagent and a suitable solvent, as shown in the scheme below:

wherein, X represents halogen or a suitable leaving group; Q, R² and m are as defined above. In a preferred embodiment, the present invention provides a novel styrene of formula (I) or a salt thereof; wherein Q represents -N=S(=O)_0-1(R⁶)(R⁷), represented as compound of formula (IA)

wherein, R², R⁶, R⁷ and m are as defined above. In a preferred embodiment, the present invention provides a novel styrene of formula (I) or a salt thereof; wherein Q represents -S(=O)_0-1(R⁵)(=NR⁴), represented as compound of formula (IB)

wherein, R², R⁴, R⁵, and m are as defined above. In a more preferred embodiment, the present invention provides a novel styrene of formula (IA-a) or a salt thereof and (IB-a) or a salt thereof wherein, R², R⁴, R⁵, R⁶ and R⁷ are as defined above. In one embodiment, the present invention provides a process for preparing the compound of formula (IA) or a salt thereof

wherein, R², R⁶, R⁷ and m are as defined above and said process comprising the steps of: a) reacting a styrene of formula (IV) or a salt thereof, wherein, X is halogen, R² and m are as defined above, with a compound of formula (V) or a salt thereof, in the presence of a suitable ligand, a metal catalyst and a suitable base to obtain a compound of formula (IA) or a salt thereof, as shown in the scheme below:

wherein, R², R⁶, R⁷ and m are as defined above, and the compound of formula (IV) or a salt thereof, is obtained either by: b) reacting a substituted benzaldehyde of formula (VI) or a salt thereof, with a Wittig’s reagent in the presence of a suitable base to obtain a styrene of formula (IV) or a salt thereof, as shown in the scheme below:

wherein X represents halogen or a suitable leaving group; R², Q and m are as defined above; or c) treating the compound of formula (III) or a salt thereof, with a suitable base to obtain a compound of formula (IV) or a salt thereof, as shown in the scheme below:

wherein R², X, Z and m are as defined above; d) further, the compound of formula (III) or a salt thereof is obtained by reacting a compound of formula (X) or a salt thereof, with a suitable cyclic ethylene derivative E of formula (II) or a salt thereof, in the presence of a suitable base, as shown in the scheme below:

wherein, the compound E represent,

; Z represents OSO₃H or COOH, or in case that Z=H the same is converted into an appropriate leaving group and R², X and m are as defined above. In another embodiment, the present invention provides a process for preparing the compound of formula (IB) or a salt thereof

wherein, R², R⁴, R⁵ and m are as defined above and said process comprising the steps of: A. reacting a compound of (VIII) or a salt thereof, with a compound of formula R⁴-Y or a salt thereof, wherein, R⁴ is as defined above and Y is X or a suitable leaving group, in the presence of a suitable base to obtain a compound of formula (IB) or a salt thereof

; wherein, Y is X or a suitable leaving group and R⁴ is as defined above; B. further, the compound of formula (VIII) or a salt thereof is obtained by reacting a substituted styrene of formula (VII) or a salt thereof, with a suitable oxidizing agent in the presence of an ammonium ion source, as shown in the scheme below:

wherein, R⁴, R⁵, and m are as defined above; and the compound of formula (VII) or a salt thereof, is obtained either by C. reacting a compound of formula (IX) or a salt thereof, with a Wittig’s reagent in the presence of a suitable base to obtain to a styrene of formula (VII) or a salt thereof, as shown in the scheme below:

D. reacting a substituted benzaldehyde of formula (VI) or a salt thereof, with a compound of formula R⁵S-M or a salt thereof to obtained the compound of formula (IX) or a salt thereof, wherein R⁵ is as defined above and M represents a metal, in the presence or absence of a suitable base, as shown in the scheme below:

wherein, R², R⁵, X and m are as defined in claim 1; and M represents a metal; or E. reacting a substituted styrene of formula (IV) or a salt thereof, with a compound of formula R⁵S-M or a salt thereof, wherein R⁵ is as defined above and M represents a metal, in the presence or absence of a suitable base to obtain a compound of formula (VII) or a salt thereof, as shown in the scheme below:

wherein R², R⁵ and X are as defined above and M represents a metal; F. obtaining the compound of formula (IV) or a salt thereof, by reacting a substituted benzaldehyde of formula (VI) or a salt thereof, with a Wittig’s reagent in presence of suitable base, as shown in the scheme below:

wherein R² and X are as defined above and M represents a metal; or G. treating the compound of formula (III) or a salt thereof, with a suitable base to obtain a styrene of formula (IV) or a salt thereof, and converting the compound of formula (IV) or a salt thereof, to the compound of formula (VII) or a salt thereof by following step (E), as shown in the scheme below:

wherein, Z represents OSO₃H or COOH, or in case that Z=H the same is converted into an appropriate leaving group; and R², R⁵ and X are as defined above; H. further the compound of formula (III) or a salt thereof is obtained by reacting a compound of formula (X) with a suitable cyclic ethylene derivative E of formula (II) or a salt thereof, in presence of suitable base, as shown in the scheme below:

wherein, the compound E represents

; Z represents OSO₃H or COOH, or in case that Z=H the same is converted into an appropriate leaving group; and R², X and m are as defined above. In another embodiment, the present invention provides a process for preparing the intermediate compound of formula (IV) or a salt thereof wherein, R², X and m are as defined above and said process comprising the steps of: I. treating the compound of formula (III) or a salt thereof, with a suitable base to obtain a styrene of formula (IV) or a salt thereof, as shown in the scheme below:

wherein, R², X, Z and m are as defined above; II. obtaining the compound of formula (III) or a salt thereof, by reacting a compound of formula (X) or a salt thereof, with a suitable cyclic ethylene derivative E of formula (II) or a salt thereof, in the presence of a suitable base, as shown in the scheme below:

wherein, the compound E represents ; Z represents OSO₃H or COOH, or in case that Z=H the same is converted into an appropriate leaving group; and R², X and m are as defined above. In a preferred embodiment, the present invention provides a process for preparing an intermediate of formula (IV) or a salt thereof

wherein, R², X and m are as defined above and, the said process comprising the steps of: I. treating the compound of formula (IIIa) or a salt thereof, with a suitable base to obtain a styrene of formula (IV) or a salt thereof, as shown in the scheme below: wherein R², X and m are as defined above; II. obtaining the compound of formula (IIIa) or a salt thereof, by reacting a compound of formula (X) or a salt thereof with a compound of formula (II-a) in the presence of a suitable base, as shown in the scheme below:

wherein, R², X and m are as defined above. In one embodiment, the present invention provides a process for preparing an intermediate of formula (IV) or a salt thereof from compound of formula (III); wherein Z represents H comprising the steps of: I. treating the compound of formula (IIIc) or a salt thereof, with a suitable base to obtain a styrene of formula (IV) or a salt thereof, as shown in the scheme below:

wherein LG is selected from chloro, bromo, iodo, tosylate (p-toluenesulfonate), triflate (trifluoromethanesulfonate), nosylate or mesylate (methanesulfonate); and R², X and m are as defined above; II. converting a compound of formula (III) or a salt thereof wherein Z represents H, to the compound of formula (IIIc) or a salt thereof, in the presence of a suitable halogenating agents or suitable sulfonyl halides as shown in the scheme below: wherein, LG is selected from chloro, bromo, iodo, tosylate (p-toluenesulfonate), triflate (trifluoromethanesulfonate), nosylate or mesylate (methanesulfonate) and R², X and m are as defined above; III. obtaining the compound of formula (III) or a salt thereof, by reacting a compound of formula (X) or a salt thereof with a compound of formula (II-b) in the presence of a suitable base, as shown in the scheme below:

wherein, R², X and m are as defined above. In a preferred embodiment, the present invention provides a process for preparing the compound of formula (IA-a) or a salt thereof

wherein, R², R⁶ and R⁷ are as defined above; and said process comprising the steps of: a) reacting a styrene of formula (IV-a) or a salt thereof, wherein, X is halogen and R², m are as defined above, with a compound of formula (V) or a salt thereof, in the presence of a suitable ligand, a metal catalyst and a base to obtain a compound of formula (IA-a) or a salt thereof, as shown in the scheme below:

wherein, the compound of formula (IV-a) or a salt thereof is obtained either by: b) reacting a substituted benzaldehyde compound of formula (VI-a) or a salt thereof, with a Wittig’s reagent in the presence of a suitable base to obtain a styrene compound of formula (IV-a) or a salt thereof, as shown in the scheme below:

or c) treating the compound of formula (III-a) or a salt thereof, with a suitable base to obtain a compound of formula (IV-a) or a salt thereof, as shown in the scheme below:

d) obtaining the compound of formula (III-a) or a salt thereof, by reacting a compound of formula (X-a) or a salt thereof, with a suitable cyclic ethylene derivative E of formula (II) or a salt thereof, in the presence of a suitable base, as shown in the scheme below:

wherein, the compound E represents

; Z represents OSO₃H or COOH, or in case that Z=H the same is converted into an appropriate leaving group. In another preferred embodiment, the present invention provides a process for preparing the compound of formula (IB-a) or a salt thereof

wherein, R², R⁴, and R⁵ are as defined above and said process comprising the steps of: A. reacting a compound of (VIII-a) or a salt thereof, with a compound of formula R⁴-Y or a salt thereof, wherein, R⁴ is as defined above and Y is X or a suitable leaving group, in the presence of a suitable base to obtain a compound of formula (IB-a) or a salt thereof, as shown in the scheme below:

B. obtaining the compound of formula (VIII-a) or a salt thereof, by reacting a substituted styrene of formula (VII-a) or a salt thereof, with a suitable oxidizing agent in the presence of an ammonium ion source, as shown in the scheme below:

wherein, the compound of formula (VII-a) or a salt thereof is obtained either by: C. reacting a compound of formula (IX-a) or a salt thereof, with a Wittig’s reagent in the presence of a suitable base to obtain to a styrene of formula (VII-a) or a salt thereof, as shown in the scheme below:

D. obtaining the compound of formula (IX-a) or a salt thereof, by reacting a substituted benzaldehyde of formula (VI-a) or a salt thereof, with a compound of formula R⁵S-M or a salt thereof, wherein R⁵ is as defined above and M represents metal, in presence or absence of a suitable base, as shown in the scheme below:

or E. reacting a substituted styrene of formula (IV-a) or a salt thereof, with a compound of formula R⁵S-M or a salt thereof, wherein R⁵ is as defined above and M represents a metal, in the presence or absence of a suitable base to obtain a compound of formula (VII-a) or a salt thereof, as shown in the scheme below:

F. obtaining the compound of formula (IV-a) or a salt thereof, by reacting a substituted benzaldehyde of formula (VI-a) or a salt thereof, with a Wittig’s reagent in the presence of a suitable base, as shown in the scheme below:

or G. treating the compound of formula (III-a) or a salt thereof, with a suitable base to obtain a styrene of formula (IV-a) or a salt thereof and converting the compound of formula (IV-a) or a salt thereof, to a compound of formula (VII-a) or a salt thereof, by following the step (E), as shown in the scheme below:

wherein, Z represents OSO₃H or COOH, or in case that Z=H the same is converted into an appropriate leaving group; H. obtaining the compound of formula (III-a) or a salt thereof, by reacting a compound of formula (X-a) or a salt thereof, with a suitable cyclic ethylene derivative E of formula (II) or a salt thereof, in the presence of a suitable base, as shown in the scheme below:

wherein, the compound E represents ; Z represents OSO₃H or COOH, or in case that Z=H the same is converted into an appropriate leaving group. In another embodiment, the present invention provides a process for preparing the intermediate of formula (IV-a) or a salt thereof

wherein, R² and X are as defined above and said process comprising the steps of: I. treating the compound of formula (III-a) or a salt thereof, with a suitable base to obtain a styrene of formula (IV-a) or a salt thereof, as shown in the scheme below:

II. obtaining the compound of formula (III-a) or a salt thereof, by reacting a compound of formula (X-a) or a salt thereof with a suitable ethylene derivative E of formula (II) or a salt thereof, in the presence of a suitable base, as shown in the scheme below:

wherein, the compound E represents

; and Z represents OSO₃H or COOH, or in case that Z=H the same is converted into an appropriate leaving group. In one embodiment, the preparation of a compound of formula (IA or IA-a) is carried out following the reaction step (a), by reacting a styrene of formula (IV or IV-a) or a salt thereof, with a compound of formula (V) or a salt thereof, in the presence of a suitable ligand, a metal catalyst and a base in a solvent at a temperature and for a period, which allows sufficient formation of a compound of formula (IA or IA-a) or a salt thereof. In one embodiment, present invention provides process for preparing the compound of formula (I) wherein, preferred substitutions: R² is selected from the group consisting of halogen, cyano, hydroxy, C₁-C₆ alkyl, C₁-C₆ alkoxy, C₁-C₆ alkylthio, C₁-C₆ haloalkyl and C₃-C₆ cycloalkyl. m is an integer selected from 1 to 2. More preferred R² is halogen. Q is selected from -S(=O)_0-1(R⁵)(=NR⁴) or -N=S(=O)_0-1(R⁶)(R⁷). More preferred Q is -N=S(=O)_0-1(R⁶)(R⁷). R⁴ is selected from the group consisting of hydrogen, C₁-C₄ alkyl, C₁-C₄ haloalkyl, C₃-C₆ cycloalkyl and C₃-C₆ cycloalkyl-C₁-C₄ alkyl; R⁵ and R⁶ are independently selected from the group consisting of C₁-C₄ alkyl, C₁-C₄ haloalkyl, C₃-C₆ cycloalkyl, C₃-C₆ cycloalkyl-C₁- C₄ alkyl, and C₃-C₆ halocycloalkyl; R⁷ is independently selected from the group consisting of C₁-C₄ alkyl, C₃-C₆ cycloalkyl, C₃-C₆ cycloalkyl-C₁-C₄ alkyl, C₁-C₄ haloalkyl, C₃-C₆ halocycloalkyl and phenyl. More preferred R⁴, R⁵ and R⁶ are C₁-C₄ alkyl. In a preferred embodiment, the present invention provides a compound of formula (I) or salts thereof is selected from:

The suitable base for carrying out the reaction step (a) is selected from a group consisting of organic base, inorganic base and organometallics base or a mixture thereof. The inorganic base is selected from metal hydride, metal hydroxide, metal carbonate metal bicarbonate, metal phosphate, wherein the metal lithium, sodium, potassium, calcium, magnesium, cesium and the like. The example of inorganic base include, but is not limited to lithium hydride, sodium hydride, potassium hydride, calcium hydride, sodium bicarbonate, sodium carbonate, calcium carbonate, cesium carbonate, lithium carbonate, potassium carbonate, lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, calcium hydroxide, sodium diphosphate, sodium phosphate, potassium diphosphate and potassium phosphate or a mixture thereof. The organic base is selected from amines, which includes but is not limited to ethylamine, triethylamine, pyridine, piperidine, N,N-(Dimethylamino)pyridine (DMAP), tetramethylammonium hydroxide tetrabutylammonium hydroxide and choline hydroxide or a mixture thereof. The organometallic base is selected from metal alkoxide or metal amide, which include but is not limited to, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium tert-butoxide, magnesium tert-butoxide, aluminium isopropoxide, titanium(IV) isopropoxide, lithium diisopropylamide (LDA), lithium tetramethylpiperidide (LiTMP), and lithium hexamethyldisilazide (LiHMDS) or a mixture thereof. Preferably, the base is selected from a group consisting of amines, metal alkoxide, metal hydride and metal amide or a mixture thereof. Most preferably, the base is selected from sodium bicarbonate, sodium carbonate, cesium carbonate, lithium carbonate or potassium carbonate. The solvent useful for step (a) is selected from the group consisting of aliphatic, alicyclic or aromatic hydrocarbons, for example petroleum ether, n-hexane, n-heptane, cyclohexane, methylcyclohexane, benzene, toluene, xylene and decalin or a mixture thereof; halogenated hydrocarbons, for example chlorobenzene, dichlorobenzene, dichloromethane, chloroform, tetrachloromethane, dichloroethane and trichloroethane or a mixture thereof; ethers such as diethyl ether, diisopropyl ether, methyl tert- butyl ether, methyl tert-amyl ether, dioxane, tetrahydrofuran, 2-methyl tetrahydrofuran, 1,2- dimethoxyethane, 1,2- diethoxyethane, cyclopentylmethylether and anisole or a mixture thereof; nitriles such as acetonitrile, propionitrile, n- orisobutyronitrile andbenzonitrile or a mixture thereof; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylformanilide, N-methylpyrrolidone and hexanlethylphosphoranlide or a mixture thereof; sulphoxides such as dimethyl sulphoxide; sulphones such as sulpholane; alcohols such as methanol, ethanol, propanol, isopropanol, butanol isobutanol, tert-butanol andamyl alcohol or a mixture thereof . Preferably, the suitable solvent is selected from the group consisting of aliphatic, alicyclic or aromatic hydrocarbons, ethers, amide, halogenated hydrocarbons and nitrile or a mixture thereof. Most preferably, the solvent is selected from ethanol, isopropanol, tetrahydrofuran, 2-methyltetrahydrofuran or a mixture thereof. The suitable ligand for reaction step (a) is selected from the group consisting of 1,1- Bis(diphenylphosphino)methane (dppm), 1,2-Bis(dimethylphosphino)ethane (dmpe), 1,2- Bis(diisopropylphosphino)ethane (dippe), 1,2-Bis(diphenylphosphino)ethane (dppe), derivative of phenylanisylmethylphosphine (DIPAMP), Bis(dicyclohexylphosphino)ethane (dcpe), 1,3- Bis(diphenylphosphino)propane (dppp), 1,4-Bis(diphenylphosphino)butane (dppb), (S,S)-DIOP (O- isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane) (DIOP), 2,3- Bis(diphenylphosphino)butane (Chiraphos), 2,2'-Bis(diphenylphosphino)-1,1'-binaphthyl (BINAP), 4,5-Bis(diphenylphosphino)-9,9-dimethylxanthene (Xantphos), Bis[(2-diphenylphosphino)phenyl] ether (DPEphos), SPANphos, SEGPHOS, 1,1'-Bis(diphenylphosphino)ferrocene (dppf), (Me- DuPhos) 1,2-Bis(2,5-dimethylphospholano)benzene (Josiphos), (Diphenylphosphino)ferrocenyl-ethyldicyclohexylphosphine1,5-Diaza-3,7-diphosphacyclooctanes. More preferably, the ligand is selected from 2,2'-Bis(diphenylphosphino)-1,1'-binaphthyl (BINAP), 4,5-Bis(diphenylphosphino)-9,9-dimethylxanthene (Xantphos), 1,2-dimethylethylenediamine (DMEDA) or 1,10-phenanthroline. The metal catalyst or organometallic compounds are compounds having bonds between one or more metal atoms and one or more carbon atoms of an organic group and may be selected from group consisting of organolithium compounds, organosodium compounds, organopotassium compounds organomagnesium, organoaluminum compounds, organocopper compounds, organonickel compounds, organozinc compounds organoplatinum(II) complexes and organopalladium. The non-limiting examples of preferable metal catalyst or organometallic compounds includes Bis(dibenzylideneacetone)palladium(0) [(Pd(dba)2)], tris(dibenzylideneacetone)dipalladium(0) [Pd2(dba)3] and the like. More preferably, the metal catalyst is selected from CuI, Cu(OAc)₂, CuSO₄.H₂O, palladium acetate or tris(dibenzylideneacetone)dipalladium(0) [Pd₂(dba)3]. The reaction temperature and duration required for completing the reaction step (a) may vary from -70 °C to 250 °C for duration of a few minutes to several hours. Preferably, the reaction temperature ranges from 0 °C to 150 °C for a period of a few minutes to 24 h. The reaction step (a) is carried out under atmospheric pressure, but can also be carried out under increased or reduced pressure and optionally under an inert atmosphere. The intermediate compound of formula (IV or IV-a) can be prepared by following the step (b), by reacting a substituted benzaldehyde compound of formula (VI or VIa) or a salt thereof, with a Wittig’s reagents in the presence of a suitable base and in a solvent at a temperature and for a period, which allows sufficient formation of a styrene of formula (IV or IV-a) or a salt thereof. The Wittig reagents also known as phosphonium ylides or alkylidene phosphoranes can be prepared by methods known per se, for example, treating tri-substituted phosphines with the alkyl halide to give phosphonium salts, which furnish the ylides upon treatment with the base such as potassium tert- butoxide. The suitable Wittig’s reagent for carrying out the reaction step (d) is selected from non- limiting examples which include methyltriphenylphosphonium chloride, methyltriphenylphosphonium bromide, methyltriphenylphosphonium iodide, and the like. The suitable base for carrying out the reaction step (b) is selected from the bases as provided for the reaction step (a). Preferably, the base is selected from metal hydroxide, metal hydride, metal alkoxide and metal amide or mixture thereof. Most preferably, the base is selected from sodium bicarbonate, sodium carbonate, cesium carbonate, lithium carbonate or potassium carbonate. The solvent for carrying out the reaction step (b) is selected from solvents, as provided for the reaction step (a). Preferably, the solvent is selected from ether, aromatic hydrocarbon, nitrile and amides or mixture thereof. Most preferably, the solvent is selected from ethanol, isopropanol, tetrahydrofuran, 2- methyltetrahydrofuran or a mixture thereof. The reaction temperature and period required for completing the reaction step (b) may vary from -70 °C to 250 °C for duration of a few minutes to several hours. Preferably the reaction temperature ranges from 0 °C to 150 °C for a period of a few minutes to 24 h. The reaction step (b) can be performed under atmospheric pressure, but can also be carried out under increased or reduced pressure and optionally under an inert atmosphere. Alternatively, the intermediate compound of formula (IV or IV-a) or a salt thereof, is prepared by following the reaction step (c), comprising treating the compound of formula (III or III-a) or a salt thereof, with a suitable base and in a solvent at a temperature and for a period, which allows sufficient formation of a compound of formula (IV or IV-a) or a salt thereof. Further, obtaining a styrene compound of formula (III) or (III-a) or salt thereof, by following the reaction step (d), by reacting the compound of formula (X) or a salt thereof, with a suitable cyclic ethylene derivative E of formula (II) or a salt thereof, in the presence of a suitable base and in a solvent at a temperature and for a period, which allows sufficient formation of a styrene compound of formula (III or IIIa). The suitable base for performing the reaction step (c) and step (d) is selected from the base as provided for reaction step (a). Preferably, the base is selected from amine, metal hydroxide, metal carbonate, metal hydride, metal alkoxide and metal amide or mixture thereof. Most preferably, the base is selected from sodium bicarbonate, sodium carbonate, cesium carbonate, lithium carbonate or potassium carbonate. The solvent for performing the reaction step (c) and step (d) is selected from the solvents as provided for reaction step (a). Preferably the solvent is selected from alcohol, amide, ethers, hydrocarbon and nitrile or mixture thereof. Most preferably, the solvent is selected from ethanol, isopropanol, tetrahydrofuran, 2-methyltetrahydrofuran or a mixture thereof. The reaction temperature and period required for completing the reaction step (c) and step (d) may vary from -70 °C to 250 °C for duration of a few minutes to several hours. Preferably the reaction temperature ranges from -70 °C to 150 °C for a period of a few minutes to 24 h. The reaction step (c) and step (d) can be performed under atmospheric pressure, but can also be carried out under increased or reduced pressure and optionally under an inert atmosphere. In another embodiment, the compound of formula (IB or IB-a) or a salt thereof, is prepared by following the reaction step (A), comprising, reacting a compound of (VIII or VIII-a) or a salt thereof, with a compound of formula R⁴-Y or a salt thereof, wherein, R⁴ is as defined above and Y is X or a suitable leaving group, in the presence of a suitable base and in a solvent at a temperature and for a period, which allows sufficient formation of a compound of formula (IB or IB-a) or a salt thereof. The suitable base for carrying out the reaction step (B) is selected from a group consisting of organic base, inorganic base and organometallics base or mixture thereof. The inorganic base is selected from metal hydride, metal hydroxide, metal carbonate metal bicarbonate, metal phosphate, wherein the metal lithium, sodium, potassium, calcium, magnesium, cesium and the like. The examples of inorganic base include, but are not limited to lithium hydride, sodium hydride, potassium hydride, calcium hydride, sodium bicarbonate, sodium carbonate, calcium carbonate, cesium carbonate, lithium carbonate, potassium carbonate, lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, calcium hydroxide, sodium diphosphate, sodium phosphate, potassium diphosphate and potassium phosphate or a mixture thereof. The organic base is selected from amines, which includes but is not limited to ethylamine, triethylamine, pyridine, piperidine, N,N-(Dimethylamino)pyridine (DMAP), tetramethylammonium hydroxide tetrabutylammonium hydroxide and choline hydroxide or a mixture thereof. The organometallic base is selected from metal alkoxide or metal amide, which include but is not limited to, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium tert-butoxide, magnesium tert-butoxide, aluminium isopropoxide, titanium (IV)isopropoxide, lithium diisopropylamide (LDA), lithium tetramethylpiperidide (LiTMP), and lithium hexamethyldisilazide (LiHMDS) or a mixture thereof. Preferably, the base is selected from a group consisting of amines, metal alkoxide, metal hydride and metal amide or a mixture thereof. Most preferably, the base is selected from sodium bicarbonate, sodium carbonate, cesium carbonate, lithium carbonate or potassium carbonate. The solvent useful for the reaction step (B) is selected from the group consisting of aliphatic, alicyclic or aromatic hydrocarbons, for example petroleum ether, n-hexane, n-heptane, cyclohexane, methylcyclohexane, benzene, toluene, xylene and decalin or a mixture thereof; halogenated hydrocarbons, for example chlorobenzene, dichlorobenzene, dichloromethane, chloroform, tetrachloromethane, dichloroethane and trichloroethane or a mixture thereof; ethers such as diethyl ether, diisopropyl ether, methyl tert-butyl ether, methyl tert-amyl ether, dioxane, tetrahydrofuran, 2- methyl tetrahydrofuran, 1,2-dimethoxyethane, 1,2- diethoxyethane, cyclopentylmethylether and anisole or a mixture thereof; nitriles such as acetonitrile, propionitrile, n- orisobutyronitrile andbenzonitrile or a mixture thereof; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, N- methylformanilide, N-methylpyrrolidone and hexanlethylphosphoranlide or a mixture thereof; sulphoxides such as dimethyl sulphoxide; sulphones such as sulpholane; alcohols such as methanol, ethanol, propanol, isopropanol, butanol isobutanol, tert-butanol andamyl alcohol or a mixture thereof. Preferably, the solvent is selected from group consisting of hydrocarbons, ethers, amide and nitrile or a mixture thereof. Most preferably, the solvent is selected from ethanol, isopropanol, tetrahydrofuran, 2- methyltetrahydrofuran or a mixture thereof. The reaction temperature and period required for completing the reaction step (B) may vary from -70 °C to 250 °C for duration of a few minutes to several hours. Preferably, the reaction temperature ranges from 0 °C to 150 °C for a period of a few minutes to 24 h. The reaction step (B) can be performed under atmospheric pressure, but can also be carried out under increased or reduced pressure and optionally under an inert atmosphere. The compound of (VIII or VIII-a) or a salt thereof, is obtained by following the reaction step (B), comprising reacting a substituted styrene of formula (VII or VII-a) or a salt thereof, with a suitable oxidizing agent in the presence of an ammonium ion source and in a solvent at a temperature and for a period which allows sufficient formation of the compound of formula (VIII or VIII-a) or a salt thereof. The suitable oxidizing agent useful for performing the reaction step (B) is selected from a group consisting of fluorine; chlorine; hydrogen peroxide; nitric acid or nitrate compounds; sulfuric acid; peroxydisulfuric acid; peroxy mono sulfuric acid; chlorite, chlorate, perchlorate and other analogus of halogen compounds; hypochlorite and other hypohalite compounds such as sodium hypochlorite; hexavalent chromium compounds such as chromic and dichromic acids, chromium trioxide, pyridinium chlorochromate, chromate/dichromate compounds; permanganate compounds such as potassium permanganate; sodium perborate; nitrous oxide, nitrogen dioxide, dinitrogen tetroxide; potassium nitrate; sodium bismuthate, iodine, iodine pentoxide, iodobenzene dichloride, iodosobenzene bis(trifluoroacetate), iodosobenzene diacetate, N-iodosuccinimide, and iodosylbenzene. More preferably, the oxidizing agent is selected from hydrogen peroxide, sodium hypochlorite, pyridinium chlorochromate, iodine pentoxide, iodobenzene dichloride, iodosobenzene bis(trifluoroacetate), iodosobenzene diacetate, N-iodosuccinimide, or iodosylbenzene. The source of ammonium ion for the reaction step (B) is selected from a group consisting of ammonium carbamate, ammonium hydroxide, ammonium carbonate, ammonium chloride, ammonium nitrate, ammonium formate, ammonium acetate and the like. The key intermediate of formula (VII or VII-a) or a salt thereof, required for the preparation of a compound of formula (IB or IB-a) or a salt thereof, is obtained by one or more of the following methods comprising reaction steps (B) and step (C) or reaction step (C) and step (D) or reaction steps (E) to (F) in a solvent at a temperature and for a period which allows sufficient formation of the respective reaction product or a salt thereof. In one embodiment, the compound of formula R⁵S-M is wherein; M represents a metal and R⁵ represent C₁-C₆ alkyl, C₂-C₆ alkenyl, C₃-C₆ cycloalkyl, C₃-C₆ cycloalkyl-C₁-C₆ alkyl, C₁-C₆ haloalkyl, and C₃-C₆ halocycloalkyl. A preferred compound of formula R⁵S-M is an alkali metal salt of thioalkoxide, wherein R⁵ is C₁-C₆-alkyl and M is selected from sodium, potassium or lithium. The metal salt of thioalkoxide is selected from a group consisting of lithium thioalkoxides, sodium thioalkoxides, or potassium thioalkoxides. The suitable examples of lithium thioalkoxides include but not limited to lithium thiomethoxide, lithium thioethoxide, lithium thiopropoxide and the likes. The suitable examples of sodium thioalkoxides include but not limited to sodium thiomethoxide, sodium thioethoxide, sodium thiopropoxide and the likes. The suitable examples of potassium thioalkoxides include but not limited to potassium thiomethoxide, potassium thioethoxide, potassium thiopropoxide and the likes In one embodiment, the reaction step (B), step (C), step (D), step (E), step (F) and step (G) may be carried out in the presence or absence of a suitable base. Preferably, the reaction step (D) and step (E) is carried out in absence of a base. The suitable base for carrying out the reaction step (B), step (C), step (D), step (E), step (F) and step (G) is selected from a group consisting of organic base, inorganic base and organometallics base or a mixture thereof. The inorganic base is selected from metal hydride, metal hydroxide, metal carbonate metal bicarbonate, metal phosphate, wherein the metal lithium, sodium, potassium, calcium, magnesium, cesium and the like. The examples of inorganic base include, but are not limited to lithium hydride, sodium hydride, potassium hydride, calcium hydride, sodium bicarbonate, sodium carbonate, calcium carbonate, cesium carbonate, lithium carbonate, potassium carbonate, lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, calcium hydroxide, sodium diphosphate, sodium phosphate, potassium diphosphate and potassium phosphate or a mixture thereof. The organic base is selected from amines, which includes but is not limited to ethylamine, triethylamine, pyridine, piperidine, N,N-(Dimethylamino)pyridine (DMAP), tetramethylammonium hydroxide tetrabutylammonium hydroxide and choline hydroxide or a mixture thereof. The organometallic base is selected from metal alkoxide or metal amide, which include but is not limited to, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium tert-butoxide, magnesium tert-butoxide, aluminium isopropoxide, titanium(IV)isopropoxide lithium diisopropylamide (LDA), lithium tetramethylpiperidide (LiTMP), and lithium hexamethyldisilazide (LiHMDS) or a mixture thereof. Preferably, the base is selected from a group consisting of amines, metal alkoxide, metal hydride and metal amide or mixture thereof. Most preferably, the base is selected from sodium bicarbonate, sodium carbonate, cesium carbonate, lithium carbonate or potassium carbonate. The suitable solvent useful for step (B), step (C), step (D), step (E), step (F), step (G) or step (H) is selected from the group is selected from group consisting of aliphatic, alicyclic or aromatic hydrocarbons, for example petroleum ether, n-hexane, n-heptane, cyclohexane, methylcyclohexane, benzene, toluene, xylene and decalin or a mixture thereof; halogenated hydrocarbons, for example chlorobenzene, dichlorobenzene, dichloromethane, chloroform, tetrachloromethane, dichloroethane and trichloroethane or a mixture thereof; ethers such as diethyl ether, diisopropyl ether, methyl tert- butyl ether, methyl tert-amyl ether, dioxane, tetrahydrofuran, 2-methyl tetrahydrofuran, 1,2- dimethoxyethane, 1,2-diethoxyethane, cyclopentylmethylether and anisole or a mixture thereof; nitriles such as acetonitrile, propionitrile, n-orisobutyronitrile andbenzonitrile or a mixture thereof; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylformanilide, N-methylpyrrolidone and hexanlethylphosphoranlide or a mixture thereof; sulphoxides such as dimethyl sulphoxide; sulphones such as sulpholane; alcohols such as methanol, ethanol, propanol, isopropanol, butanol isobutanol, tert- butanol andamyl alcohol or a mixture thereof. Preferably, the solvent is selected from group consisting of hydrocarbons, ethers, amide and nitrile or mixture thereof. Most preferably, the solvent is selected from ethanol, isopropanol, tetrahydrofuran, 2-methyltetrahydrofuran or a mixture thereof. The reaction temperature and period required for completing the reaction step (B), step (C), step (D), step (E), step (F) or step (G) may vary from -70 °C to 250 °C for a duration of a few minutes to several hours. Preferably the reaction temperature ranges from 0 °C to 150 °C for a period of a few minutes to 24 h. Further, the reaction step (B), step (C), step (D), step (E), step (F) or step (G) can be performed under atmospheric pressure, but can also be carried out under increased or reduced pressure and optionally under an inert atmosphere. The suitable Wittig’s reagent for carrying out the reaction step (B) and step (E) is selected from non- limiting examples which include methyltriphenylphosphonium chloride, methyltriphenylphosphonium bromide, methyltriphenylphosphonium iodide, and the likes. In another embodiment, the present invention also provides a process for preparing the intermediate of formula (IV or IV-a) or salts thereof, by following the reaction step (I) and step (II) in a solvent at a temperature and for a period which allows sufficient formation of the respective reaction product or a salt thereof. The suitable base and solvent for carrying out the reaction step (I) and step (II) is selected from the bases and solvents as provided for the reaction step (a) or step (A). The reaction temperature and period required for completing the reaction step (I) and step (II) or may vary from -70 °C to 250 °C for duration of a few minutes to several hours. Preferably, the reaction temperature ranges from 0 °C to 150 °C for a period of a few minutes to 24 h. The reaction step (I) and step (II) can be performed under atmospheric pressure, but can also be carried out under increased or reduced pressure and optionally under an inert atmosphere. In one embodiment, the preparation of a compound of formula (IA or IA-a), (IB or IB-a) and (IV or IV- a) may involve isolation of the respective reaction intermediates after the completion of the reaction. However, the reaction steps can also be proceed to the next steps without isolation of the respective reaction intermediates. The processes as disclosed in the present invention are preferably carried out batch-wise. However, semi-continuous or continuous reaction passages, e.g., under flow conditions, are also possible. The process as disclosed in the present invention can be run in the absence of a solvent or in the presence of one or more suitable solvents. The optional solvent should be resistant against oxidation (i.e. a solvent will be preferred whose rate of oxidation is substantially lower than that of the compounds of formula (I or X-a) to (IX or IX-a) and suitable for suspending, or preferably dissolving the reactants. Any person skilled in the art knows the best work-up procedure of the reaction mixtures after the end of the respective reactions. In one embodiment, the work-up is usually carried out by isolation of the product by filtration, and optionally washing with solvent, further optionally drying of the product if required. The isolation of the reaction product can also be carried out by a technique which includes but is not limited to decantation, centrifugation, evaporation, liquid-liquid extraction, distillation, recrystallization, chromatography and the like. The process steps according to the invention are generally carried out under atmospheric pressure. Alternatively, however, it is also possible to work under increased or reduced pressure. Without further elaboration, it is believed that any person skilled in the art who is using the preceding description can utilize the present invention to its fullest extent. The following examples are therefore to be interpreted as merely illustrative and not limiting of the disclosure in any way whatever. EXAMPLES The invention is further illustrated with reference to the following examples as represented in Scheme A, Scheme B and Scheme C. It is apparent to those skilled in the art that many modifications, both to materials, methods and various reaction parameters, may be practiced without departing from the scope of the invention. The starting materials according to the present invention are known compounds that are commercially available or can be prepared in a known manner. Following examples are given by way of illustration and therefore should not be construed to limit the scope of the invention. Scheme-A

Scheme-B

Scheme-C Examples: Example 1: Preparation of ((3-fluoro-2-vinylphenyl)imino)dimethyl-l6-sulfanone (IA-a1) Step (a): Preparation of ((3-fluoro-2-vinylphenyl)imino)dimethyl-l6-sulfanone (IA-a1) To a stirred suspension of 1-bromo-3-fluoro-2-vinylbenzene (IV-a1, 10 g, 49.7 mmol), iminodimethyl- l6-sulfanone (V-a1, 5.10 g, 54.7 mmol) and sodium tert-butoxide (6.21 g, 64.7 mmol) in toluene (100 mL), argon gas was purged for 20-30 min at 25 °C. To this reaction mixture, xantphos (1.44 g, 2.49 mmol) and tris(dibenzylideneacetone)dipalladium(0) (2.28 g, 2.49 mmol) were added. The reaction mixture was heated to 80 °C and stirred for 6 h under an argon atmosphere. After completion of the reaction, the reaction mixture was filtered through a celite bed and the filtrate obtained was washed with water (25 mL) and brine solution (25 mL). The organic layer was dried over sodium sulphate, filtered and concentrated under reduced pressure to obtained a brown sticky material, which was purified by column chromatography (eluent: 30 % ethyl acetate in hexane) to obtain ((3-fluoro-2- vinylphenyl)imino)dimethyl-l6-sulfanone (IA-a1, 7.4 g, 34.7 mmol, 69.8 % yield). ¹H-NMR (400 MHz, chloroform-d): δ 6.99-7.07 (2H, m), 6.89 (1H, dd, J = 12.0, 18.0 Hz), 6.69-6.75 (1H, m), 5.96 (1H, dd, J = 1.6, 18.0 Hz), 5.45 (1H, dd, J = 1.6, 12.0 Hz), 3.15 (6H, s); MS: 214.35 (M+1). The preparation of the intermediate 1-bromo-3-fluoro-2-vinylbenzene (IV-a1) can be synthesised either by Process-I or Process-II. Process-I Step a(i): Preparation of 2-bromo-6-fluorophenethyl hydrogen sulfate (III-a1) To a solution of N,N-diisopropyl amine (0.98 g, 9.71 mmol) in anhydrous tetrahydrofuran (10 mL) at - 70 °C, a solution of n-butyl lithium in cyclohexane (2M, 4.29 mL, 8.57 mmol) was added in drop wise manner. The reaction mixture was stirred at the same temperature for 1.5 h and then allowed to warm up to 0 °C during 30 min. The reaction mixture was again cooled to -70 °C, after which 1-bromo-3- fluorobenzene (I-a1, 1 g, 5.7 mmol) was added in a drop wise manner and stirring was continued for further 30 min. Then a solution of ethylene sulfate (II-a, 0.851 g, 6.86 mmol) in tetrahydrofuran (4 mL) was added to the reaction mixture in a drop wise manner. After completion of the addition, the reaction mixture was further stirred at -70 °C for 1h and then gradually warmed up to 20-25 °C and stirred further for 16 h. After completion of the reaction, the reaction mixture was cooled to 0 °C, quenched by adding 1N hydrochloride solution and stirred further for 15 min. The mixture was then extracted with ethyl acetate (2 x 20 mL), the combined organic layers were washed with brine solution (10 mL), dried over sodium sulphate, filtered and concentrated under reduced pressure to obtain 2-bromo-6-fluorophenethyl hydrogen sulfate (III-a1, 1.67 g, 97.7%). ¹H-NMR (400 MHz, DMSO-d6) δ 7.43-7.48 (m, 1H), 7.19-7.27 (m, 2H), 3.84-3.76 (m, 2H), 3.01 (td, J = 7.5, 2.0 Hz, 2H); ¹⁹F-NMR (377 MHz, DMSO-d6) δ -111.9; MS: 297.05 [M-1]. Step a(ii): Preparation of 1-bromo-3-fluoro-2-vinylbenzene (IV-a1) Method-1: To a solution of 2-bromo-6-fluorophenethyl hydrogen sulfate (III-a1, 0.2 g, 0.669 mmol) in N,N- dimethylformamide (7 mL), sodium hydroxide (53 mg, 1.33 mmol) was added. The reaction mixture was heated at 85 °C and stirred for 2 h. After completion of the reaction, the reaction mixture was poured into water (10 mL) and stirred for 10 min. The resulting mixture was extracted with methyl tert- butyl ether (2 x 10 mL). The combined organic layer was washed with brine solution (20 mL), dried over sodium sulphate, filtered and concentrated under reduced pressure to obtain 1-bromo-3-fluoro-2- vinylbenzene (IV-a1, 126 mg, 94% yield). ¹H-NMR (400 MHz, CHLOROFORM-d): δ 7.36-7.39 (1H, m), 7.01-7.09 (2H, m), 6.76 (1H, dd, J = 12.0, 17.8 Hz), 5.93 (1H, dd, J = 1.6, 17.8 Hz), 5.63 (1H, dd, J = 1.6, 12.0 Hz); MS: 200.0 [M⁺] Method-2: To a solution of 2-bromo-6-fluorophenethyl hydrogen sulfate (III-a1, 0.2 g, 0.669 mmol) in N,N- dimethylformamide (7 mL), potassium hydroxide (75 mg, 1.33 mmol) was added. The reaction mixture was heated at 85 °C and stirred for 2 h. After completion of the reaction, the reaction mixture was poured into water (10 mL) and stirred for 10 min. The obtained mixture was extracted with methyl tert- butyl ether (2 x 10 mL). The combined organic layers were washed with brine solution (20 mL), dried over sodium sulphate, filtered and concentrated under reduced pressure to obtain 1-bromo-3-fluoro-2- vinylbenzene (IV-a1, 121 mg, 90% yield). ¹H-NMR (400 MHz, CHLOROFORM-d): δ 7.36-7.39 (1H, m), 7.01-7.09 (2H, m), 6.76 (1H, dd, J = 12.0, 17.8 Hz), 5.93 (1H, dd, J = 1.6, 17.8 Hz), 5.63 (1H, dd, J = 1.6, 12.0 Hz); MS: 200.0 [M⁺] Method-3: To a solution of 2-bromo-6-fluorophenethyl hydrogen sulfate (III-a1, 0.3 g, 1.003 mmol) in tert-butanol (10 mL), potassium tert-butoxide (338 mg, 3.01 mmol) was added. The reaction mixture was heated at 85 °C and stirred for 2 h. After completion of the reaction, the reaction mixture was poured into water (10 mL) and stirred for 10 min. The resulting mixture was extracted with methyl tert-butyl ether (2 x 10 mL). The combined organic layer was washed with brine solution (20 mL), dried over sodium sulphate, filtered and concentrated under reduced pressure to obtain 1-bromo-3-fluoro-2-vinylbenzene (IV-a1, 190 mg, 90% yield). ¹H-NMR (400 MHz, CHLOROFORM-d): δ 7.36-7.39 (1H, m), 7.01-7.09 (2H, m), 6.76 (1H, dd, J = 12.0, 17.8 Hz), 5.93 (1H, dd, J = 1.6, 17.8 Hz), 5.63 (1H, dd, J = 1.6, 12.0 Hz); MS: 199.9 [M⁺] Process-II Step a(iii): Preparation of 1-bromo-3-fluoro-2-vinylbenzene (IV-a1) To a suspension of potassium tert-butoxide (27.6 g, 246 mmol) in tetrahydrofuran (200 mL), methyltriphenylphosphonium bromide (52.8 g, 148 mmol) was added in portions at 25 °C. The reaction mixture was stirred for 15 min and then cooled to 0 - 5 °C. To the resulting mixture, a solution of 2- bromo-6-fluorobenzaldehyde (VI-a1, 25 g, 123 mmol) in tetrahydrofuran (50 mL) was introduced drop wise, followed by further 15 min stirring at the same temperature. The reaction mixture was slowly warmed up to 25 °C, with stirring for further 1 h. After completion of the reaction, the reaction mixture was cooled to 0 °C and quenched by the addition of saturated aqueous ammonium chloride solution. Stirring was continued for 15 min, after which the mixture was extracted with ethyl acetate (2 x 100 mL). The combined organic layers were washed with brine (50 mL), dried over sodium sulphate, filtered and concentrated under reduced pressure to afford a crude material, which was further purified by column chromatography (eluent: n-hexane) to obtain 1-bromo-3-fluoro-2-vinylbenzene (IV-a1, 16 g, 80 mmol, 65% yield). ¹H-NMR (400 MHz, chloroform-d): δ 7.36-7.39 (1H, m), 7.01-7.09 (2H, m), 6.76 (1H, dd, J = 12.0, 17.8 Hz ), 5.93 (1H, dd, J = 1.6, 17.8 Hz), 5.63 (1H, dd, J = 1.6, 12.0 Hz). Example 2: Preparation of (3-fluoro-2-vinylphenyl)(methyl)(methylimino)-l6-sulfanone (IB-a1). Step (b): Synthesis of (3-fluoro-2-vinylphenyl)(methyl)(methylimino)-l6-sulfanone (IB-a1) To a solution of (3-fluoro-2-vinylphenyl)(imino)(methyl)-l6-sulfanone (VIII-a1, 0.075 g, 0.376 mmol) in N,N-dimethylformamide (2 mL), sodium hydride (0.045 g, 0.753 mmol) was added at 0 °C and stirred for 10 min. To the resulting mixture, methyl iodide (0.022 mL, 0.452 mmol) was added drop wise at 0 °C and stirred further for 10 min. The reaction mixture was then allowed to stir at room temperature for further 2 h. After completion of the reaction, the reaction mixture was quenched by the addition of ice water (5 mL), stirred for 10 min and extracted with ethyl acetate (2 x 5 mL). The combined organic layers were washed with cooled water (2 x 5 mL), brine solution (5 mL) and then concentrated under reduced pressure to obtain 3-fluoro-2-vinylphenyl)(methyl)(methylimino)-l6-sulfanone (IB-a1, 0.060 g, 0.281 mmol, 75% yield). ¹H-NMR (400 MHz, CHLOROFORM-D): δ 7.91 (1H, d, J = 7.6 Hz), 7.28-7.44 (2H, m), 7.26-7.31 (1H, m), 5.85-5.95 (1H, m), 5.75-5.80 (1H, m), 3.14 (3H, s), 2.64 (3H, s); MS: 213.80 [M+1]⁺. Step (c): Preparation of (3-fluoro-2-vinylphenyl)(imino)(methyl)-l6-sulfanone (VIII-a1) To a solution of (3-fluoro-2-vinylphenyl)(methyl)sulfane (VII-a1, 0.200 g, 1.189 mmol) in methanol (5 mL), iodobenzene diacetate (1.149 g, 3.57 mmol) and ammonium carbamate (0.371 g, 4.76 mmol) were added at room temperature. The reaction mixture was stirred at 25 °C for 1 h. After completion of the reaction, the reaction mixture was concentrated under reduced pressure to get a sticky mass, which was purified by column chromatography (eluent: 50 % ethyl acetate in n-hexane) to obtain (3-fluoro-2- vinylphenyl)(imino)(methyl)-16-sulfanone (VIII-a1, 0.17 g, 0.853 mmol, 72% yield). ¹H-NMR (400 MHz, DMSO-D6): δ 7.82-7.89 (1H, m), 7.50-7.61 (2H, m), 7.38 (1H, dd, J = 11.6, 17.2 Hz), 7.74-5.83 (2H, m), 3.05 (3H, s); MS: 200.30 [M+1]⁺. The preparation of the (3-fluoro-2-vinylphenyl)(methyl)sulfane (VIII-a1) intermediate was achieved either by Process-I or Process-II or Process-III). Process-I Step c(i): Preparation of 2-fluoro-6-(methylthio)benzaldehyde (IX-a1) To a solution of 2,6-difluorobenzaldehyde (VI-a1 g, 14.07 mmol) in dimethyl sulfoxide (5 mL), a solution of sodium thiomethoxide (0.660 g, 9.42 mmol) in dimethyl sulphoxide (5 mL) was added drop wise at 25 °C under a nitrogen atmosphere and then stirred for 12 h. After completion of the reaction, the reaction mixture was poured into water (20 mL). The obtained precipitate was filtered, washed with water (5 mL) and dried to obtain 2-fluoro-6-(methylthio)benzaldehyde (IX-a1, 1.8 g, 10.58 mmol, 75 % yield). ¹H-NMR (400 MHz, CHLOROFORM-d): δ 10.50 (1H, s), 7.47-7.52 (1H, m), 7.07 (1H, d, J = 8.0 Hz), 6.88-6.92 (1H, m), 2.47 (3H, s). Step c(ii): Preparation of (3-fluoro-2-vinylphenyl)(methyl)sulfane (VII-a1) To a suspension of potassium tert-butoxide (0.65 g, 5.88 mmol) in tetrahydrofuran (7 mL), methyltriphenylphosphonium bromide (1.05 g, 2.94 mmol) was added portion wise at 25 °C, followed by stirring for 15 min. The reaction mixture was cooled to 0 to 5 °C, and a solution of 2-fluoro-6- (methylthio)benzaldehyde (IX-a1, 0.5 g, 2.94 mmol) in tetrahydrofuran (3 mL) was added. The reaction mixture was stirred for 15 min at the same temperature and then slowly warmed up to 25 °C with stirring for further 1 h. The reaction progress was monitored by TLC (mobile phase: n-hexane). After completion of the reaction, the reaction mixture was cooled to 0 °C and quenched with a saturated aqueous ammonium chloride solution, followed by stirring for 15 min. The mixture was extracted with ethyl acetate (2 x 5 mL), the combined organic layers were washed with a brine solution (5 mL), dried over sodium sulphate, filtered and concentrated under reduced pressure to afford a crude material, which was further purified by column chromatography (eluent: n-hexane) to obtain (3-fluoro-2- vinylphenyl)(methyl)sulfane (VII-a2, 0.36g, 2.94 mmol, 73 % yield). ¹H-NMR (400 MHz, CHLOROFORM-d): δ 7.14-7.20 (1H, m), 7.01 (1H, d, J = 3.3, 7.9 Hz ), 6.86-6.91 (1H, m ), 6.78 (1H, dd, J = 17.9, 11.7 Hz), 5.86 (1H, dd, J =1.6, 17.9 Hz), 5.62 (1H, dd, J =1.6, 11.7 Hz), 2.47 (3H, s). Process-II Step c(iii): Preparation of 1,3-difluoro-2-vinylbenzene (IV-a1) To a suspension of potassium tert-butoxide (15.8 g, 141 mmol) in tetrahydrofuran (70 mL), methyltriphenylphosphonium bromide (25.1 g, 70.4 mmol) was added in portions at 25 °C and stirred for 15 min. The reaction mixture was cooled to 0 to 5 °C and a solution of 2,6-difluorobenzaldehyde (VI-a1, 10 g, 70.4 mmol) in tetrahydrofuran (30 mL) was added. The reaction mixture was stirred for 15 min at the same temperature and then slowly warmed up to 25 °C, followed by stirring for further 1 h. After completion of the reaction, the reaction mixture was cooled to 0 °C and quenched by addition of a saturated aqueous ammonium chloride solution and further 15 min of stirring. The mixture was extracted with ethyl acetate (2 x 50 mL), the combined organic layers were washed with a brine solution (30 mL), dried over sodium sulphate, filtered and concentrated under reduced pressure to obtain a crude material, which was further purified by column chromatography (eluent: n-hexane) to obtain 1,3- difluoro-2-vinylbenzene (IV-a1, 6.8 g, 70.4 mmol, 69 % yield). ¹H-NMR (400 MHz, CHLOROFORM-d): δ 7.11-7.19 (1H, m), 6.83-6.90 (2H, m), 6.73 (1H, dd, J = 12.0, 18.2 Hz ), 6.04 (1H, dd, J = 1.6, 18.2 Hz), 5.58 (1H, dd, J = 1.6, 12.0 Hz). Step c(iv): Preparation of (3-fluoro-2-vinylphenyl)(methyl)sulfane (IV-a1) To a solution of 1,3-difluoro-2-vinylbenzene (IV-a1, 2 g, 14.27 mmol) in dimethyl sulphoxide (5.00 mL), a solution of sodium thiomethoxide (0.660 g, 9.42 mmol) in dimethyl sulfoxide (5 mL) was added in portions under a nitrogen atmosphere at 25 °C, followed by 12 h of stirring. After completion of the reaction, the reaction mixture was poured into water (20 mL) and stirred for 10 min. The mixture was extracted with ethyl acetate (2 x 10 mL), the combined organic layers were washed with a brine solution (10 mL), dried over sodium sulphate, filtered and concentrated under reduced pressure. The obtained residue was further purified by column chromatography (eluent: 5 % ethyl acetate in n-hexane) to obtain (3-fluoro-2-vinylphenyl)(methyl)sulfane (VII-a1, 1.6 g, 9.51 mmol, 67 % yield). ¹H-NMR (400 MHz, CHLOROFORM-d): δ 7.14-7.19 (1H, m), 7.00 (1H, d, J = 7.6 Hz ), 6.86-6.90 (1H, m), 6.78 (1H, dd, J = 17.6, 12.0 Hz), 5.86 (1H, dd, J = 17.6, 1.6 Hz), 5.63 (1H, dd, J = 1.6, 12.0 Hz), 2.46 (3H, s). Example 3: Preparation of ((3-fluoro-2-vinylphenyl)imino)dimethyl-l6-sulfanone (IA-a1) Method A: Pd catalyzed synthesis of ((3-fluoro-2-vinylphenyl)imino)dimethyl-l6-sulfanone (IA- a1)

To a stirred suspension of 1-bromo-3-fluoro-2-vinylbenzene ((IV-a1, 100 g, 497 mmol), iminodimethyl-λ6-sulfanone (V-a1, 51 g, 547 mmol), and sodium tert-butoxide (66.9 g, 696 mmol) in toluene (1000 ml) was purged with argon gas for 20-30 min at 25°C. Then, xantphos (2.88 g, 4.97 mmol) and Pd2(dba)3 (4.56 g, 4.97 mmol) were added to the reaction mixture. The reaction mixture was stirred at 110 ⁰C for 6 h under argon atmosphere. After completion of the reaction, the reaction mixture was filtered through a celite bed and washed with toluene (2 × 100 mL). Filtrate was washed with water (250 mL) and brine solution (250 mL). The organic layer was dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure to get a brown sticky crude material. Resulting crude material was stirred in n-heptane (300 ml) for 8 h at 25 °C. The obtained solid was filtered, washed with n-heptane (100 ml) and dried under reduced pressure to obtain ((3-fluoro-2- vinylphenyl)imino)dimethyl-λ6-sulfanone (IA-a1, 88 g, 413 mmol, 83 % yield) as an off-white solid. ¹H-NMR (400 MHz, CDCl3): δ 6.99-7.07 (2H, m), 6.89 (1H, dd, J = 12.0, 18.0 Hz), 6.69-6.75 (1H, m), 5.96 (1H, dd, J = 1.6, 18.0 Hz), 5.45 (1H, dd, J = 1.6, 12.0 Hz), 3.15 (6H, s). MS: m/z 214.00 [M+1]⁺. Method B: Cu catalyzed synthesis of ((3-fluoro-2-vinylphenyl)imino)dimethyl-λ6-sulfanone (IA- a1) from bromo styrene (IV-a1) To a stirred suspension of 1-bromo-3-fluoro-2-vinylbenzene (IV-a1, 0.5 g, 2.48 mmol), sodium iodide (NaI) (1.4 g, 9.34 mmol), copper iodide (CuI) (0.23 g, 1.20 mmol), 1,2-dimethylethylenediamine (DMEDA) (0.21 g, 2.38 mmol) and N,N-dimethylformamide (5 mL), were heated at 110 ⁰C for 6 h. To this reaction mixture, iminodimethyl-λ6-sulfanone (V-a1, 0.23g, 2.46 mmol) and t-BuOK (0.83g, 7.39 mmol) were added and the heating for was continued for 14 h. After completion of the reaction, the reaction mixture was cooled to 25 °C, diluted with water (25 ml), Ethyl acetate (EtOAc) (25 mL) and filtered through a celite bed. The celite bed was washed with ethyl acetate (2 × 50 mL). The combined filtrate was washed with water (50 mL), brine solution (50 mL), dried over anhydrous Na₂SO₄ and concentrated under reduced pressure to obtain ((3-fluoro-2-vinylphenyl)imino)dimethyl-λ6-sulfanone (IA-a1, 0.51 g, 67% purity) as a gummy material. The crude material was purified by silica gel column to obtain an off-white solid. ¹H-NMR (400 MHz, CDCl3): δ 6.99-7.07 (2H, m), 6.89 (1H, dd, J = 12.0, 18.0 Hz), 6.69-6.75 (1H, m), 5.96 (1H, dd, J = 1.6, 18.0 Hz), 5.45 (1H, dd, J = 1.6, 12.0 Hz), 3.15 (6H, s). MS: m/z 214.00 [M+1]⁺. Method C: Cu catalyzed synthesis of ((3-fluoro-2-vinylphenyl)imino)dimethyl-l6-sulfanone (IA- a1) from iodo styrene

A stirred suspension of 1-iodo-3-fluoro-2-vinylbenzene (IV-a1, 1 g, 4.03 mmol), iminodimethyl- λ6-sulfanone (V-a1, 0.563 g, 6.05 mmol), and copper iodide (CuI) (0.384 g, 2.016 mmol) in dry N,N-dimethylformamide (10 ml) was purged with argon gas for 15 min at 25-30 °C. To this suspension, 1,2-dimethylethylenediamine (DMEDA) (0.355 g, 4.03 mmol) was added and stirred at 25-30 °C for 5 min followed by the addition of potassium tert-butoxide (1.357 g, 12.09 mmol). The reaction mixture was stirred further at 110 ⁰C for 12 h under argon atmosphere. After completion of the reaction, the reaction mixture was filtered through a celite bed and washed with ethyl acetate (2 × 100 ml). The filtrate was washed with water (250 mL) and brine solution (250 mL), dried over anhydrous Na₂SO₄, and concentrated under reduced pressure to get a crude product. This crude product was further purified by silica gel column chromatography to obtain ((3-fluoro-2- vinylphenyl)imino)dimethyl-λ⁶-sulfanone (IA-a1) as an off white solid. ¹H-NMR (400 MHz, CDCl₃): δ 7.07-6.98 (m, 2H), 6.88 (dd, J = 18.2, 12.1 Hz, 1H), 6.74-6.69 (m, 1H), 5.98-5.93 (m, 1H), 5.44 (dt, J = 12.0, 2.2 Hz, 1H), 3.14 (d, J = 3.9 Hz, 6H). ¹⁹F-NMR (377 MHz, CDCl₃): δ -114. MS: m/z 214.00 [M+1]⁺. The preparation of the intermediate 1-bromo-3-fluoro-2-vinylbenzene (IV-a1) can be realised either by Process-I or Process-II. Process-I: Synthesis of 1-bromo-3-fluoro-2-vinylbenzene (IV-a1) via Wittig approach

To a suspension of potassium tert-butoxide (27.6 g, 246 mmol) in tetrahydrofuran (THF) (200 ml), methyltriphenylphosphonium bromide (52.8 g, 148 mmol) was added in portions at 25 °C and stirred for 15 min. The reaction mixture was cooled to 0 to 5°C followed by dropwise addition of a solution of 2-bromo-6-fluorobenzaldehyde (VI-a1, 25 g, 123 mmol) in tetrahydrofuran (THF) (50 mL). The reaction mixture was stirred for 15 min at 0 to 5°C and then slowly warmed to 25 °C with stirring for further 1 h. After completion of the reaction, the mixture was cooled to 0°C and quenched with saturated aqueous NH₄Cl solution and stirred for 15 min. The reaction mixture was extracted with ethyl acetate (EtOAc) (2 × 100 mL), the organic layer was washed with brine (50 mL), dried over anhydrous Na₂SO₄, filtered and concentrated under reduced pressure to obtain a crude material. The crude material was further purified by column chromatography (eluent: n-hexane) to obtain 1- bromo-3-fluoro-2-vinylbenzene (IV-a1, 16 g, 80 mmol, 64.6 % yield) as a colourless oil. ¹H-NMR (400 MHz, CDCl₃): δ 7.36-7.39 (1H, m), 7.01-7.09 (2H, m), 6.76 (1H, dd, J = 12.0, 17.8 Hz), 5.93 (1H, dd, J = 1.6, 17.8 Hz), 5.63 (1H, dd, J = 1.6, 12.0 Hz). Process-II: Synthesis of 1-bromo-3-fluoro-2-vinylbenzene (IV-a1) via ortho-metallation approach

Step a(i): Preparation of 2-bromo-6-fluorophenethyl hydrogen sulfate (III-a1) To a solution of diisopropylamine (0.98 g, 9.71 mmol) in anhydrous tetrahydrofuran (THF) (10 mL) at -70°C, 2M solution of n-butyllithium in cyclohexane (4.29 mL, 8.57 mmol) was added in a dropwise manner. The reaction mixture was stirred at -70°C for 1.5 h followed by 0 °C for 30 min. The reaction mixture was again cooled to -70 °C, 1-bromo-3-fluorobenzene I-a1 (1 g, 5.7 mmol) was added to the reaction mixture in drop wise manner and stirred further for 30 min at the same temperature. A solution of ethylene sulfate II (0.851 g, 6.86 mmol) in tetrahydrofuran (THF) (4 mL) was added to reaction mixture in drop wise manner. After complete addition, the reaction mixture was further stirred at -70 °C for 1h and then gradually warmed to 20-25 °C and stirred further for 16 h. After completion of the reaction, the reaction mixture was cooled to 0 °C and quenched with 1N HCl solution and stirred for 15 min. The reaction mixture was extracted with Ethyl acetate (EtOAc) (2 × 20 mL), washed with brine solution (10 mL), dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure to obtain 2-bromo-6-fluorophenethyl hydrogen sulfate III-a1 (1.67 g, 97.7%) as an off-white solid. ¹H-NMR (400 MHz, DMSO-D6): δ 7.43-7.48 (m, 1H), 7.19-7.27 (m, 2H), 3.84-3.76 (m, 2H), 3.01 (td, J = 7.5, 2.0 Hz, 2H). Step a(ii): Preparation of 1-bromo-3-fluoro-2-vinylbenzene (IV-a1) To a solution of 2-bromo-6-fluorophenethyl hydrogen sulfate III-a1 (0.2 g, 0.669 mmol) in N,N- dimethylformamide (7 mL), sodium hydroxide (NaOH) (53 mg, 1.33 mmol) was added. The reaction mixture was heated to 85 °C and stirred for 2 h. After completion of the reaction, the mixture was poured into water (10 mL) and stirred for 10 min. The reaction mixture was extracted with MTBE (2 × 10 mL), washed with brine solution (20 mL), dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure to obtain 1-bromo-3-fluoro-2-vinylbenzene IV-a1 (26 mg, 94% yield) as a colourless oil. ¹H-NMR (400 MHz, CDCl₃): δ 7.36-7.39 (1H, m), 7.01-7.09 (2H, m), 6.76 (1H, dd, J = 12.0, 17.8 Hz), 5.93 (1H, dd, J = 1.6, 17.8 Hz), 5.63 (1H, dd, J = 1.6, 12.0 Hz). Process-III: Preparation of 1-fluoro-3-iodo-2-vinylbenzene (IV-a1) via orthometallation approach

Step a(i): Preparation of 2-fluoro-6-iodophenethyl hydrogen sulfate (III-a1) To a solution of diisopropylamine (1.94 ml, 13.66 mmol) in anhydrous tetrahydrofuran (THF) (10ml), 2 M solution of n-butyllithium in cyclohexane (6.30 ml, 12.61 mmol) was added dropwise at -70 °C. The reaction mixture was stirred at -70 °C for 1.5 h followed by 0 °C for 30 min. The reaction mixture was again cooled to -70 °C followed by dropwise addition of 1-fluoro-3- iodobenzene (I-a1, 3.11 g, 10.51 mmol) and stirred further for 30 min at the same temperature. A solution of ethylene sulfate II (1.56 g, 12.61 mmol) in tetrahydrofuran (THF) (10 ml) was added to the reaction mixture in dropwise manner. After complete addition, the reaction mixture was further stirred at -70 °C for 1 h, followed by gradually warming to 20-25 °C and stirred further for 16 h. After completion of the reaction, the mixture was cooled to 0 °C and quenched with 1N HCl solution and stirred for 15 min. The reaction mixture was extracted with Ethyl acetate (EtOAc) (2 × 20 mL), washed with brine solution (10 mL), dried over anhydrous Na₂SO₄, filtered and concentrated under reduced pressure to obatin 2-fluoro-6-iodophenethyl hydrogen sulfate (III-a1) as an off-white solid (3.5 g, 96%). ¹H-NMR (400 MHz, DMSO-D6): δ 8.04 (s, 1H) (acidic proton), 7.67 (d, J = 7.8 Hz, 1H), 7.23-7.19 (m, 1H), 7.05 (td, J = 8.1, 5.9 Hz, 1H), 3.80-3.77 (m, 2H), 2.99 (td, J = 7.6, 2.1 Hz, 2H). Process-IV: Preparation of 1-iodo-3-fluoro-2-vinylbenzene (IV-a1) To a solution of 2-fluoro-6-iodophenethyl hydrogen sulfate (III-a1, 4.2 g, 12.13 mmol) in tetrahydrofuran (THF) (40 mL), sodium hydroxide (NaOH) (1.48 g, 36.4 mmol) was added. The reaction mixture was heated to 65 °C and stirred for 4 h. After completion of the reaction, the reaction mixture was poured into water (10 mL) and stirred for 10 min. The reaction mixture was extracted with n-hexane (2 × 10 mL), washed with brine solution (20 mL), dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure to obtain 1-iodo-3-fluoro-2-vinylbenzene (IV-a1) as colourless oil with yield of 2.2 g (73.1%). ¹H-NMR (400 MHz, DMSO-D6): δ 7.73 (dt, J = 7.8, 0.9 Hz, 1H), 7.29-7.23 (m, 1H), 7.06 (td, J = 8.1, 5.8 Hz, 1H), 6.55 (dd, J = 17.9, 11.7 Hz, 1H), 5.76-5.71 (m, 1H), 5.64-5.60 (m, 1H).

Claims

CLAIMS: 1. A compound of formula (I):

Formula (I) wherein, R² is selected from the group consisting of halogen, cyano, hydroxy, C₁-C₆-alkyl, C₁-C₆-alkoxy, C₁-C₆-alkylthio, C₁-C₆-haloalkyl, C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl, C₁-C₆-alkylsulfinyl, and C₁-C₆-alkylsulfonyl; m is an integer selected from 0 to 3; Q is selected from -N=S(=O)_0-1(R⁶)(R⁷) or -S(=O)_0-1(R⁵)(=NR⁴); R⁴ is selected from the group consisting of hydrogen, cyano, hydroxy, C₁-C₆-alkyl, C₃-C₆- cycloalkyl, C₃-C₆-cycloalkyl-C₁-C₆alkyl, C₁-C₆-alkylcarbonyl and C₁-C₆-haloalkyl carbonyl; R⁵ and R⁶ are independently selected from the group consisting of C₁-C₆-alkyl, C₂-C₆-alkenyl, C₃-C₆-cycloalkyl, C₃-C₆-cycloalkyl-C₁-C₆alkyl, C₁-C₆-haloalkyl, C₃-C₆-halocycloalkyl and phenyl; R⁷ is independently selected from the group consisting of C₁-C₆-alkyl, C₂-C₆-alkenyl, C₃-C₆- cycloalkyl, C₃-C₆-cycloalkyl-C₁-C₆alkyl, C₁-C₆-haloalkyl and C₃-C₆-halocycloalkyl; R⁴ or R⁵ with the C atom contiguous to the C atom substituted with Q may form a 4- to 6- membered heterocyclic ring, wherein the C atoms of the heterocyclic ring may be optionally replaced by C(=O) or C(=S); R⁶ and R⁷ together with the S atom to which they are attached may form a 4- to 6- membered heterocyclic ring, wherein the C atoms of the heterocyclic ring may be optionally replaced by C(=O) or C(=S); or R⁴ or R⁵ or R⁶ with the R² may form a 4- to 6- membered heterocyclic ring, wherein the C atoms of the heterocyclic ring may be optionally replaced by C(=O) or C(=S); or R⁶ or R⁷ with the C atom contiguous to the C atom substituted with Q may form a 4- to 6- membered heterocyclic ring, wherein the C atoms of the heterocyclic ring may be optionally replaced by C(=O) or C(=S); wherein, said heterocyclic rings may be optionally substituted with the group consisting of halogen, cyano, C₁-C₆-alkyl, C₃-C₆-cycloalkyl, C₁-C₆-haloalkyl or C₃-C₆- halocycloalkyl; or salts, stereo-isomers, and polymorphs thereof; with the proviso that 6-fluoro- 2-methyl-7-vinyl-3H-2λ⁴-benzo[c]isothiazole-2-oxide.

2. The compound of formula (I) as claimed in claim 1, wherein said compound of formula (I) is a compound of formula (IA)

wherein, R² is selected from the group consisting of halogen, cyano, hydroxy, C₁-C₆ alkyl, C₁-C₆ alkoxy, C₁-C₆ alkylthio, C₁-C₆ haloalkyl and C₃-C₆ cycloalkyl. m is an integer selected from 1 to 2. R⁶ is selected from the group consisting of C₁-C₄ alkyl, C₁-C₄ haloalkyl, C₃-C₆ cycloalkyl, C₃- C₆ cycloalkyl-C₁-C₄ alkyl, and C₃-C₆ halocycloalkyl; R⁷ is selected from the group consisting of C₁-C₄ alkyl, C₃-C₆ cycloalkyl, C₃-C₆ cycloalkyl-C₁- C₄ alkyl, C₁-C₄ haloalkyl, C₃-C₆ halocycloalkyl and phenyl. 3. The compound of formula (IA) as claimed in claim 2, wherein said compound of formula (IA) is a compound of formula (IA-a)

wherein, R², R⁶ and R⁷ are as defined in claim 2. 4. The compound of formula (I) as claimed in claim 1, wherein said compound of formula (I) is compound of formula (IB)

wherein, R² is selected from the group consisting of halogen, cyano, hydroxy, C₁-C₆ alkyl, C₁-C₆ alkoxy, C₁-C₆ haloalkyl and C₃-C₆ cycloalkyl. m is an integer selected from 1 to 2. R⁴ is selected from the group consisting of hydrogen, C₁-C₄ alkyl, C₁-C₄ haloalkyl, C₃-C₆ cycloalkyl and C₃-C₆ cycloalkyl-C₁-C₄ alkyl; R⁵ is selected from the group consisting of C₁-C₄ alkyl, C₁-C₄ haloalkyl, C₃-C₆ cycloalkyl, C₃- C₆ cycloalkyl-C₁-C₄ alkyl, and C₃-C₆ halocycloalkyl. 5. The compound of formula (IB) as claimed in claim 4, wherein said compound of formula (IB) is a compound of formula (IB-a)

wherein, R², R⁴ and R⁵ are as defined in claim 4. 6. A process for preparing the compound of formula (I) as claimed in claim 1, wherein said process comprising the step of: converting a compound of formula (IV) or a salt thereof, to the compound of formula (I) or a salt thereof, in the presence of a suitable reagent and a suitable solvent

wherein, X represents halogen or a suitable leaving group; R², Q and m are as defined in claim 1. 7. The process as claimed in claim 6, wherein said compound of formula (I) is the compound of formula (IA)

wherein, R², R⁶, R⁷ and m are as defined in claim 1. 8. The process as claimed in claim 6 or 7, wherein said process for preparing compound of formula (IA) further comprises the steps of: a) reacting a styrene of formula (IV) or a salt thereof, with a compound of formula (V) or a salt thereof, in the presence of a suitable ligand, a metal catalyst and a base to obtain a compound of formula (IA) or a salt thereof wherein, R², R⁶, R⁷ and m are as defined in claim 1; b) reacting a substituted benzaldehyde of formula (VI) or a salt thereof, with a Wittig’s reagent in the presence of a suitable base to obtain a styrene of formula (IV) or a salt thereof as defined in step (a)

wherein X represents halogen or a suitable leaving group; R², Q and m are as defined in claim 1; or c) treating the compound of formula (III) or a salt thereof, with a suitable base to obtain a compound of formula (IV) or a salt thereof as defined in step (a)

wherein R², X, Z and m are as defined in claim 1; d) reacting a compound of formula (X) or a salt thereof, with a suitable cyclic ethylene derivative E of formula (II) or a salt thereof, in the presence of a suitable base, to obtain the compound of formula (III) or a salt thereof as defined in step (c)

wherein, the compound E represent

Z represents H, OSO₃H or COOH; R², X and m are as defined in claim 1.

. The process as claimed in claim 8, wherein said compound of formula (IA) is the compound of formula (IA-a). 10. The process as claimed in claim 6, wherein said compound of formula (I) is the compound of formula (IB)

wherein, R², R⁴, R⁵ and m are as defined in claim 1. 11. The process as claimed in claim 6 or 10, wherein said process for preparing compound of formula (IB) further comprises the steps of: A. reacting a compound of (VIII) or a salt thereof, with a compound of formula R⁴-Y or a salt thereof, in the presence of a suitable base to obtain a compound of formula (IB) or a salt thereof

wherein, Y is X or a suitable leaving group and R⁴ is as defined in claim 1; B. reacting a substituted styrene of formula (VII) or a salt thereof, with a suitable oxidizing agent in the presence of an ammonium ion source, to obtain the compound of formula (VIII) or a salt thereof as defined in step (A)

wherein, R², R⁵, and m are as defined in claim 1; C. reacting a compound of formula (IX) or a salt thereof, with a Wittig’s reagent in the presence of a suitable base to obtain to a styrene of formula (VII) or a salt thereof as defined in step (B)

wherein, R², R⁵, and m are as defined in claim 1; D. reacting a substituted benzaldehyde of formula (VI) or a salt thereof, with a compound of formula R⁵S-M or a salt thereof, in the presence or absence of a suitable base, to obtained the compound of formula (IX) or a salt thereof as defined in step (C)

wherein, R², R⁵, X and m are as defined in claim 1; and M represents a metal; or E. reacting a substituted styrene of formula (IV) or a salt thereof, with a compound of formula R⁵S-M or a salt thereof, in the presence or absence of a suitable base to obtain a compound of formula (VII) or a salt thereof as defined in step (C)

wherein R², R⁵ and X are as defined above and M represents a metal; F. obtaining the compound of formula (IV) or a salt thereof as defined in step (E), by reacting a substituted benzaldehyde of formula (VI) or a salt thereof, with a Wittig’s reagent in presence of suitable base

wherein R² and X are as defined in claim 1; and M represents a metal; or G. treating the compound of formula (III) or a salt thereof, with a suitable base to obtain a styrene of formula (IV) or a salt thereof as defined in step (E), and converting the compound of formula (IV) or a salt thereof, to the compound of formula (VII) or a salt thereof by following step (E) wherein, Z is H, OSO₃H or COOH; and R², R⁵ and X are as defined in claim 1; H. obtaining the compound of formula (III) or a salt thereof as defined in step (F) by reacting a compound of formula (X) with a suitable cyclic ethylene derivative E of formula (II) or a salt thereof, in presence of suitable base

wherein, the compound E represents

; Z represents H, OSO₃H or COOH; R², X and m are as defined in claim 1. 12. The process as claimed in claim 11, wherein said compound of formula (IB) is the compound of formula (IB-a). 13. The process as claimed in claim 8 or 11, wherein said process for preparing the compound of formula (IV) or a salt thereof, further comprising the steps of: I. treating the compound of formula (III) or a salt thereof, with a suitable base to obtain a styrene of formula (IV) or a salt thereof

wherein, Z represents H, OSO₃H or COOH; R², X and m are as defined in claim 1; II. obtaining the compound of formula (III) or a salt thereof as defined in step I, by reacting a compound of formula (X) or a salt thereof, with a suitable cyclic ethylene derivative E of formula (II) or a salt thereof, in the presence of a suitable base

wherein, the compound E represents

Z represents H, OSO₃H or COOH; R², X and m are as defined in claim 1. 14. The process as claimed in claim 13, wherein said compound of formula (E) is

, represented as compound of formula (IIa) and the compound of formula (III) is

, represented as compound of formula (IIIa). 15. The process as claimed in claim 8, wherein the step (a) comprises a ligand is selected from 2,2'- Bis(diphenylphosphino)-1,1'-binaphthyl (BINAP), 4,5-Bis(diphenylphosphino)-9,9- dimethylxanthene (Xantphos), 1,2-dimethylethylenediamine (DMEDA) or 1,10-phenanthroline; a metal catalyst is selected from CuI, Cu(OAc)2 or CuSO4.H2O, palladium acetate or tris(dibenzylideneacetone)dipalladium(0) [Pd2(dba)3]; a base is selected from sodium tert- butoxide, potassium tert-butoxide, sodium carbonate, cesium carbonate or potassium carbonate. 16. The process as claimed in claim 8, wherein the step (b) comprises Wittig’s reagent is selected from methyltriphenylphosphonium chloride, methyltriphenylphosphonium bromide, methyltriphenylphosphonium iodide; a base is selected from sodium bicarbonate, sodium carbonate, cesium carbonate, lithium carbonate or potassium carbonate; and a solvent is selected from acetonitrile, 2-methyl tetrahydrofuran, tetrahydrofuran, N,N-dimethylformamide or a mixture thereof. 17. The process as claimed in claim 8, wherein the step (c) and step (d) comprises a base is selected from sodium bicarbonate, sodium carbonate, cesium carbonate, lithium carbonate or potassium carbonate. 18. The process as claimed in claim 11, wherein the compound of formula R⁵S-M is an alkali metal salt of thioalkoxide; wherein the alkali metal is selected from sodium, potassium or lithium.

19. The process as claimed in claim 11, wherein the step (A) comprises a base is selected from sodium bicarbonate, sodium carbonate, cesium carbonate, lithium carbonate or potassium carbonate. 20. The process as claimed in claim 11, wherein the step (B) comprises oxidizing agent is selected from hydrogen peroxide, sodium hypochlorite, pyridinium chlorochromate, iodine pentoxide, iodobenzene dichloride, iodosobenzene bis(trifluoroacetate), iodosobenzene diacetate, N- iodosuccinimide, or iodosylbenzene; ammonium ion is selected from ammonium carbamate, ammonium hydroxide, ammonium carbonate, ammonium chloride, ammonium nitrate, ammonium formate, or ammonium acetate; and a solvent is selected from acetonitrile, 2-methyl tetrahydrofuran, tetrahydrofuran, N,N-dimethylformamide or a mixture thereof. 21. The process as claimed in claim 11, wherein the step (C) and (F) comprises Wittig’s reagent is selected from methyltriphenylphosphonium chloride, methyltriphenylphosphonium bromide, methyltriphenylphosphonium iodide; and a base is selected from sodium bicarbonate, sodium carbonate, cesium carbonate, lithium carbonate or potassium carbonate. 22. The process as claimed in claim 11, wherein the step (D), step (E), step (G) and step (H) comprises a base is selected from sodium bicarbonate, sodium carbonate, cesium carbonate, lithium carbonate or potassium carbonate.