Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D401/00—Heterocyclic compounds containing two or more hetero rings, having nitrogen atoms as the only ring hetero atoms, at least one ring being a six-membered ring with only one nitrogen atom
  • C07D401/02—Heterocyclic compounds containing two or more hetero rings, having nitrogen atoms as the only ring hetero atoms, at least one ring being a six-membered ring with only one nitrogen atom containing two hetero rings
  • C07D401/12—Heterocyclic compounds containing two or more hetero rings, having nitrogen atoms as the only ring hetero atoms, at least one ring being a six-membered ring with only one nitrogen atom containing two hetero rings linked by a chain containing hetero atoms as chain links
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K31/00—Medicinal preparations containing organic active ingredients
  • A61K31/33—Heterocyclic compounds
  • A61K31/395—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins
  • A61K31/435—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins having six-membered rings with one nitrogen as the only ring hetero atom
  • A61K31/44—Non condensed pyridines; Hydrogenated derivatives thereof
  • A61K31/445—Non condensed piperidines, e.g. piperocaine
  • A61K31/4523—Non condensed piperidines, e.g. piperocaine containing further heterocyclic ring systems
  • A61K31/454—Non condensed piperidines, e.g. piperocaine containing further heterocyclic ring systems containing a five-membered ring with nitrogen as a ring hetero atom, e.g. pimozide, domperidone
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P9/00—Drugs for disorders of the cardiovascular system
  • A61P9/04—Inotropic agents, i.e. stimulants of cardiac contraction; Drugs for heart failure
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/72—Copper
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
  • B01J27/06—Halogens; Compounds thereof
  • B01J27/08—Halides
  • B01J27/122—Halides of copper
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D231/00—Heterocyclic compounds containing 1,2-diazole or hydrogenated 1,2-diazole rings
  • C07D231/02—Heterocyclic compounds containing 1,2-diazole or hydrogenated 1,2-diazole rings not condensed with other rings
  • C07D231/10—Heterocyclic compounds containing 1,2-diazole or hydrogenated 1,2-diazole rings not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members
  • C07D231/12—Heterocyclic compounds containing 1,2-diazole or hydrogenated 1,2-diazole rings not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members with only hydrogen atoms, hydrocarbon or substituted hydrocarbon radicals, directly attached to ring carbon atoms
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D231/00—Heterocyclic compounds containing 1,2-diazole or hydrogenated 1,2-diazole rings
  • C07D231/02—Heterocyclic compounds containing 1,2-diazole or hydrogenated 1,2-diazole rings not condensed with other rings
  • C07D231/10—Heterocyclic compounds containing 1,2-diazole or hydrogenated 1,2-diazole rings not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members
  • C07D231/14—Heterocyclic compounds containing 1,2-diazole or hydrogenated 1,2-diazole rings not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
  • C07D231/18—One oxygen or sulfur atom
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D403/00—Heterocyclic compounds containing two or more hetero rings, having nitrogen atoms as the only ring hetero atoms, not provided for by group C07D401/00
  • C07D403/02—Heterocyclic compounds containing two or more hetero rings, having nitrogen atoms as the only ring hetero atoms, not provided for by group C07D401/00 containing two hetero rings
  • C07D403/12—Heterocyclic compounds containing two or more hetero rings, having nitrogen atoms as the only ring hetero atoms, not provided for by group C07D401/00 containing two hetero rings linked by a chain containing hetero atoms as chain links
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/50—Improvements relating to the production of bulk chemicals
  • Y02P20/55—Design of synthesis routes, e.g. reducing the use of auxiliary or protecting groups

Definitions

• the present invention provides processes for preparation of substituted pyrazole compounds of formula II, that can be used as intermediates for preparation of substituted piperidine urea compounds useful for the treatment of dilated cardiomyopathy (DCM).
• DCM dilated cardiomyopathy
• R is independently selected from F, C 1 -C 4 alkyl, C 1 -C 4 haloalkyl; and R is independently selected from H, F, C 1 -C 4 alkyl, C 1 -C 4 haloalkyl,
• R 4 is C 1 -C 4 alkyl
• R 6 is H or a protecting group or salt thereof
• R is selected from H, Cl or trialkylsilyl.
• DCM dilated cardiomyopathy
• R 1 is a 5 to 6-membered heteroaryl ring having at least one nitrogen atom and is optionally substituted with one or more selected from halo, cyano, hydroxyl, C1-C4 alkyl, C1-C4 haloalkyl, and C1-C4 alkoxy.
• WO2016/118774 discloses preparation of 4-methylsulphonyl substituted piperidine urea compounds using reagents like N-Fluorodibenzenesulfonimide, (NFSI), diethylaminosulfur trifluoride, lithiated compounds that are strong, expensive reagents and are not viable for commercial scale up of 4-methylsulphonyl substituted piperidine urea compounds.
• reagents like N-Fluorodibenzenesulfonimide, (NFSI), diethylaminosulfur trifluoride, lithiated compounds that are strong, expensive reagents and are not viable for commercial scale up of 4-methylsulphonyl substituted piperidine urea compounds.
• the present invention provides processes for preparation of substituted pyrazole compounds of formula II that can be used as intermediates for preparation of compound of formula I.
• the present invention provides processes for preparation of substituted pyrazole compounds of formula II that can be used as intermediates for the preparation of substituted piperidine urea compounds useful for treatment of dilated cardiomyopathy (DCM).
• DCM dilated cardiomyopathy
• R 2 is independently selected from F, C 3
• R is independently selected from H, F, C1-C4 alkyl, C1-C4 haloalkyl,
• R 4 is Ci-C4 alkyl
• R 6 is H or a protecting group or salt thereof
• R is selected from H, Cl or trialkylsilyl.
• the present invention provides a process for preparation of a compound of formula II,
• R 2 is independently selected from F, C 1 -C 4 alkyl, C 1 -C 4 haloalkyl
• R 3 is independently selected from H, F, C 1 -C 4 alkyl, C 1 -C 4 haloalkyl
• R 4 is C 1 -C 4 alkyl, R 6 is H or a protecting group or salt thereof and R 7 is a group selected from H, Cl or trialkylsilyl;
• L 2 is a leaving group
• R 6 is as defined above
• the present invention provides a process for preparation of a compound of formula II,
• R is independently selected from F, C 1 -C 4 alkyl, C 1 -C 4 haloalkyl; and R is independently selected from H, F, C 1 -C 4 alkyl, C 1 -C 4 haloalkyl, R 4 is C 1 -C 4 alkyl, R 6 is H or a protecting group or salt thereof and R 7 is selected from H, Cl or trialkylsilyl;
• R 3 and R 4 are as defined above, n is 2-8; Li is selected from a leaving group;
• L 2 is a leaving group
• the present invention provides a process for preparation of a compound of formula II
• R 2 , R 3 , R 4 R 6 and R 7 are as defined above;
• the present invention provides a process for preparation of a compound of formula II, wherein the steps of fluorination and oxidization are carried out without isolating the compound of formula IV.
• the present invention provides a process for preparation of a compound of formula IV,
• R 3 , R 4 , R 6 and R 7 are as defined above.
• the present invention provides a process for preparation of a compound of formula III,
• R 3 , R 4 , R 6 and R 7 are as defined above.
• the present invention provides a compound of formula VI,
• R 3 , R 4 , R 7 and Li are as defined above.
• the present invention provides a process for preparation of a compound of formula V,
• R 3 , R 4 , R 6 and R 7 are as defined above;
• R , R and R are as defined above;
• the present invention provides a process for preparation of a compound of formula V,
• R 3 , R 4 , R 6 and R 7 are as defined above;
• R , R and R are as defined above;
• the present invention provides a compound of formula II and salts thereof.
• R 6 is H or salt thereof.
• the present invention provides a pyrazole compound of formula III
• R 3 , R 4 and R 6 are as defined above.
• the present invention provides pyrazole compound of formula IV,
• R 3 , R 4 and R 6 are as defined above.
• C 1 -C 4 alkyl in the present invention refers to methyl, ethyl, isopropyl, n- butyl, iso-butyl, tert-butyl, or the like.
• C 1 -C 4 haloalkyl in the present invention refers to alkyl group substituted by one or more halogens. Examples of C 1 -C 4 haloalkyl include, but not limited to fluoromethyl, difluoromethyl, trifluoromethyl, fluoroethyl, difluoroethyl, trifluoroethyl, tetrafluoroethyl, or the like.
• C 1 -C 4 alkoxy in the present invention refers to methoxy, ethoxy, propoxy, isopropoxy, butoxy or the like.
• ambient temperature in the present invention refers to the temperature in the range of 5°C to 35°C.
• heteroaryl in the present invention refers to 5-6 membered heteroaromatic ring having at least one nitrogen atom as a ring member.
• salt in the present invention refers to hydrochloride, hydrobromide, mesylate, tosylate or the like.
• protecting group in the present invention refers to the groups used in the art and serve the function of blocking amino moiety while the reactions are carried out at other sites of the molecule.
• amino protecting groups include, but not limited to acyl, alkoxycarbonyl, alkenyloxycarbonyl and aralkyloxycarbonyl groups such as carbobenzyloxy, tert.-butoxycarbonyl, trityl, pthaloyl, and the like.
• deprotection in the present invention refers to the process of removal of protecting group.
• the step of deprotection is carried out by a procedure known in the art or as described in Protecting Groups by Carey & Sundberg, which is included as a reference.
• the step can be carried out using an acid such as hydrochloric acid, hydrobromic acid, acetic acid or trifluoroacetic acid, or a base such as sodium hydroxide or potassium hydroxide.
• the term“leaving group” in the present invention refers to an atom or a group of atoms which can be displaced during the reaction.
• the leaving group includes but are not limited to organosulphonyl groups, acyloxy groups, alkoxy groups, alkoxy carbonyl groups (e.g., ethoxy carbonyl or the likes); halogens (e.g., iodine, bromine, chlorine or fluorine); amido; azido; isocyanato; substituted or unsubstituted thiolates (e.g., thiomethyl or thiophenyl).
• the Examples of leaving groups include mesyl, tosyl, bromo, iodo, and the like.
• a catalyst, used in the step of formation of compound of formula VI/VIB/VIC, is selected from the salts of copper or iron.
• the catalyst includes copper chloride (CuCl), copper bromide (CuBr), copper iodide (Cul), iron chloride (FeCl 3 ), Iron bromide (FeBr 3 ) or the like.
• reducing agent in the present invention refers to Zinc/acetic acid, Zinc/alcoholic potassium hydroxide, sodium borohydride, potassium borohydride, lithium aluminum hydride, triphenylphosphine/HCl, and tris(2- carboxyethyl)phosphine, borane, triphenylphosphine, tributylphosphine, tris(2- carboxyethyl)phosphine, or the like.
• base in the present invention refers to inorganic or organic bases.
• inorganic bases include potassium carbonate, sodium carbonate, cesium carbonate, sodium bicarbonate, sodium hydride, potassium hydride, or the like.
• organic bases includes sodium ethoxide, sodium methoxide, lithium tert- butoxide, sodium tert-butoxide, potassium tert-butoxide, triethylamine, n-butylamine, t-butylamine, pyridine, methyl lithium, n-butyl lithium, lithium diisopropylamide, lithium 2,2,6,6-tetramethylpziperidine, sodium bis(trimethylsilyl)amide, lithium bis(trimethylsilyl)amide, potassium bis(trimethylsilyl)amide, lithium diethylamide or the like.
• the step of fluorination in the present invention is carried out in presence of electrophilic fluorinating agents.
• electrophilic fluorinating agents includes N-fluoro-o-benzenedisulfonimide, N-fluorobenzenesulfonimide, 1- chloromethyl-4-fluoro- 1 ,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate), N- fluoro-pyridinium salts such as l-fluoropyridinium triflate, l-fluoropyridinium tetrafluoroborate, l-fluoro-2,4,6-trimethylpyridinium tetrafluoroborate, 1-Fluoro- 2,4,6-trimethylpyridinium triflate, l-fluoro-2,6-dichloropyridinium triflate, 2,6- dichloro- l-fluoropyridinium tetrafluoroborate, 2-
• the fluorinating agents are selected from a group consisting of l-fluoropyridinium triflate, 1- fluoropyridinium tetrafluoroborate, 1 -fluoro-2,4,6-trimethylpyridinium tetrafluoroborate, 1 -fluoro-2,4,6-trimethylpyridiniumtriflate, 1 -fluoro-2,6- dichloropyridinium triflate, 2,6-dichloro-l-fluoropyridinium tetrafluoroborate, 1- fluoro-4-methylpyridinium triflate, l-fluoro-4-methylpyridinium tetrafluoroborate.
• the step of oxidation is carried out using an oxidant, optionally in the presence of a catalyst to oxidize sulfide to sulfone.
• a catalyst to oxidize sulfide to sulfone.
• the oxidant includes hydrogen peroxide/sodium tungstate, peracetic acid, benzyl hydroperoxide, ethylbenzene hydroperoxide, cumyl hydroperoxide, sodium hypochlorite, oxalic acid dihydrate/hydrogen peroxide (H 2 0 2 ), meta-chloroperoxybenzoic acid (mCPBA), urea- hydrogen peroxide adduct, Permanganate/manganese dioxide, Ruthenium chloride hydrate/sodium periodate, oxone, and the like, optionally in the presence of catalyst, for example, ammonium molybdate or alkali metal tungstate.
• the step of alkylation is carried out using alkylating gent in the presence of a base.
• the alkylating agent includes but is not limited to bromoalkane, chloroalkane, iodoalkane, diazoalkane, dialkylcarbonate, dialkylsulfonate, and the like.
• the present invention provides a process for preparation of a compound of formula II,
• R is independently selected from F, C1-C4 alkyl, C1-C4 haloalkyl; and R is selected from H, F, C1-C4 alkyl, C1-C4 haloalkyl, R 4 is C1-C4 alkyl,
• R 6 is H or a protecting group or salt thereof and R 7 is selected from H, Cl or trialkylsilyl;
• R 6 is as defined above, L 2 is a leaving group
• the present invention provides a process for preparation of a compound of formula II, wherein R and R represent methyl and R represents difluoromethyl.
• the present invention provides a process for preparation of a compound of formula II, converting a compound of formula VI or VIB to a compound of formula V ; fluorinating the compound of formula V to a compound of formula IV followed by oxidizing the compound of formula IV to a compound of formula III, wherein in compounds of formulae II, V, IV, and III, R and R represent methyl and R represents difluoromethyl and are represented as the compounds of formulae IIA, VIA, VIC, VA, IVA and IIIA respectively.
• the present invention provides compounds of formulae IIA, VIA, VIC, VA, IV A and IIIA.
• the present invention provides a process for preparing t-butyl- 4- ⁇ 1 - [3 -(difluoromethyl) - 1 -methyl- 1 H-pyrazole-4- sulfonyl] - 1 -fluoroethyl ⁇ piperidine carboxylate comprising the steps of:
• present invention provides a process for preparing t-butyl-4- ⁇ 1 - [3 -(difluoromethyl) - 1 -methyl- 1 H-pyrazole-4- sulfonyl] - 1 -fluoroethyl Jpiperidine carboxylate comprising the steps of:
• step a) of reacting a compound of formula VII with sulfur is carried out in the presence of a base selected from a group consisting of potassium carbonate, sodium carbonate, cesium carbonate or the like.
• step a) of reacting a compound of formula VII with a sulfur is optionally carried out in the presence an additive agent, selected from a group that includes potassium iodide, sodium iodide or dimethylaminopyridine (DMAP) or the like.
• an additive agent selected from a group that includes potassium iodide, sodium iodide or dimethylaminopyridine (DMAP) or the like.
• the step a) of reacting a compound of formula VII with a sulfur is carried out in a solvent.
• solvents includes dimethylformamide, dimethylacetamide, ethyl methyl ketone, acetone, methyl isopropyl ketone, methyl isobutyl ketone, methyl n-butyl ketone, methyl t-butyl ketone, methyl isoamyl ketone, dimethyl sulfoxide, sulfolane, hexamethylphosphoric triamide, tetrahydrofuran, dioxane, dimethoxyethane, diethylene glycol, dimethyl ether, diethylether, dichloromethane, dichloroethane, chloroform, carbon tetrachloride, toluene, ethyl acetate, acetonitrile, or mixture(s) thereof.
• the step a) of reacting a compound of formula VII with a sulfur is carried out in presence of a reducing agent selected from a group consisting of triphenylphosphine, tributylphosphine, tris(2- carboxyethyl)phosphine, or the like.
• the step b) of reacting a compound of formula WVIA/VIB with a compound of formula VIII is carried out in presence of base.
• reaction does not involve isolation of the compound of formula VI or VIA.
• reaction does not involve isolation of the compound of formula VI or VIA.
• the step of fluorination is carried out in presence of an electrophilic fluorinating agent.
• the step of fluorination is carried out in the presence of N- fluoro-pyridinium salts.
• the compound of formula IVA may not be isolated.
• the compound of formula IIIA may not be isolated.
• the step of oxidation may precede step of fluorination.
• present invention provides a process that does not involve isolation of either tert-butyl-4-[ ⁇ [3-(difluoromethyl)-l-methyl-lH- pyrazol-4-yl] sulfanyl ⁇ (fluoro)methyl]piperidine-l -carboxylate or 4- ⁇ [3-
• the present invention provides a process for preparation tert-butyl-4- ⁇ 1 - [3 -(difluoromethyl)- 1 -methyl- 1 H-pyrazole-4- sulfonyl] - 1 - fluoroethyl ⁇ piperidine-l -carboxylate, wherein, the step of fluorination and oxidation occurs without isolation of tert-butyl 4-[ ⁇ [3-(difluoromethyl)-l-methyl-lH-pyrazol-4- yl] sulfanyl ⁇ (fluoro)methyl]piperidine- 1 -carboxylate.
• R 6 and R 7 are as defined above, comprising the steps of:
• present invention involves a step of hydrolysis of compound of formula IIA, wherein R is Cl or alkylsilyl group, to a compound of formula IIA, wherein R is hydrogen.
• present invention involves a step of de-protection of the compound of formula IIA, wherein R 6 is a protecting group, to a compound of formula IIA, wherein R 6 is hydrogen.
• present invention provides a compound of formula IIB and salts thereof in purity of 95% to 99%.
• present invention provides 4- ⁇ l-[3-(difluoromethyl)-l- methyl-lH-pyrazole-4-sulfonyl]-l-fluoroethyl ⁇ piperidine and salts thereof.
• present invention provides a process for using a compound of formula IIB or salt thereof for preparation of compound of formula I.
• present invention involves isolation of a compound of formula IIC as a solid compound
• R 6 is tert-butyloxycarbonyl and R 7 is hydrogen.
• the compound of formula IIC is isolated in crystalline and/or amorphous form. The isolation of the compound of formula IIC is carried out using crystallization in a suitable solvent or mixture of solvents at a temperature of about -20°C to 30°C.
• the solvents used in the crystallization can be selected from the group consisting of methanol, ethanol, propanol, 2-propanol, tetrahydrofuran, acetonitrile, cyclohexane, hexane, heptane, toluene, water or the like and the mixture thereof.
• present invention provides a pyrazole compound of formula IIIA,
• R 6 is as defined above.
• present invention provides tert-butyl-4- ⁇ [3-(difluoromethyl)- 1 -methyl- 1 H-pyrazole-4- sulfonyl] (fluoro)methyl ⁇ piperidine- 1 -carboxylate.
• present invention provides a process for using a compound of formula IIIA for preparation of compound of formula I.
• An aspect of the present invention provides compound of formulae II, IIA, IIB, IIC, III and/or IIIA as impurity in the compound of formula I.
• the compound of formulae II and III can be converted to the compound of formula I using the methods known or taught in WO 2016118774, which is included as a reference.
• present invention provides a process for preparation of compound of formula II, wherein the process does not involve isolation of the intermediate of formula VIB.
• the process for conversion of a compound of formula V to a compound of formula II involves the step of fluorination, followed by oxidation and subsequent alkylation or permutation and combination of these steps to give a compound of formula II.
• tert-butyl 4-( ⁇ [3-(difluoromethyl)-l-methyl-lH-pyrazol-4- yl]sulfanyl ⁇ methyl)piperidine-l -carboxylate is fluorinated using an electrophilic fluorinating agent to yield tert-butyl-4- ⁇ [3 -(difluoromethyl) -1 -methyl- lH-pyrazole-4- sulfonyl](fluoro)methyl ⁇ piperidine-l-carboxylate, which upon oxidation and subsequent methylation yields tert-butyl-4- ⁇ l-[3-(difluoromethyl)-l-methyl-lH- pyrazole-4- sulfonyl] - 1 - P uorocthy 1 ⁇ pipcridi nc- 1 -carboxylate.
• the compounds of formulae II, III, IV, and V can be used for preparation of compound of formula I.
• the compounds of formulae V and VA can be converted to a compound of formula II, by the methods taught in WO 2016118774 which are included as reference.
• the compounds of formula II can be converted to the compound of formula I using the methods known or taught in WO 2016118774, which is included as a reference.
• the compound of formula VII and VIII, used as starting material can either be obtained commercially or be prepared by the method as disclosed in PCT Pub. No. 2009/000442 and US Pub. No. 2010/29650.
• the compound of formula VIB can also be obtained commercially or can be prepared by the method as disclosed in Chinese Pub. No. 105622469.
• Pyrazole carboxylic acid used as a raw material can either be obtained commercially or be prepared by the method described in US Pat. No. 9650345.
• the present invention provides a process for preparation of 3-(difluoromethyl)-4-iodo-l-methyl-lH-pyrazole comprising the step of decarboxylation of 3-(difluoromethyl)-l-methyl-lH-pyrazole-4-carboxylic acid using Cu powder and Cu20 in presence of aliphatic amine in polar aprotic solvent followed by the step of iodination of 3 -(difluoromethyl)- 1 -methyl- lH-pyrazole using iodine and potassium iodate in presence of acetic acid and sulphuric acid.
• aliphatic amine examples include methylamine, ethylamine, triethylamine, diethylmethylamine, isopropylamine, disopropylamine, diisopropylmethylamine, diisopropylethylamine, n- butylamine, tertiary butylamine, tributylamine, or the like.
• Embodiments of the invention are not mutually exclusive, but may be implemented in various combinations. The described embodiments of the invention and the disclosed examples are given for the purpose of illustration rather than limitation of the invention as set forth in the appended claims.
• Tributylamine (90gm, 0.48mol) was added to a mixture of 3-(difluoromethyl)-l- methyl-lH-pyrazole-4-carboxylic acid (l70gm, 0.966mol), Cu Powder (l0.8gm, 0.176 mol), and Cu 2 0 (9.67gm, 0.067mol) in sulfolane (252gm, 2.lmol) at ambient temperature.
• the reaction mixture was stirred at l50°C for six hours. After completion of the reaction, the product is distilled off from the reaction under vacuum. Tributylamine was recycled back to the reactor.
• Hydrochloric acid (35%; 42ml) was slowly added to the reaction mass while maintaining the temperature of reaction mixture to below 30°C. After completion of the addition, the reaction mixture was stirred at a temperature of about 40°C. The reaction mixture was concentrated at a temperature of about 80°C to obtain a residue. Water (700ml) and dichloromethane (l50ml ) were added to the residue and stirred for about l5minutes. The pH of the mixture was adjusted to 4.5-5 and layers were separated. Aqueous layer was again extracted with dichloromethane (60ml). The organic layers were combined and filtered and washed with water. A solution of potassium hydroxide (20%; 80ml) was added to the organic layer. The organic layer was washed with water, passed through sodium sulfate bed and concentrated to obtain the desired compound.
• EXAMPLE 11 Preparation of tert-butyl 4-( ⁇ [3-(difluoromethyl)-l-methyl-lH- pyrazol-4-yl]sulfanyl ⁇ methyl)piperidine-l-carboxylate using 4,4'- disulfanediylbis[3-(difluoromethyl)-l-methyl-lH-pyrazole]
• LiHMDS (1M; 14.6ml) was dropwise added to a solution of tert-butyl-4- ⁇ [3- (difluoromethyl)- 1 -methyl- 1 H-pyrazole-4-sulfonyl] (fluoro)methyl ⁇ piperidine- 1 - carboxylate (2 gm, 0.0048 mol) in THF (45 ml) under nitrogen atmosphere.
• the reaction mixture was cooled to -78 °C and stirred for 20 minutes.
• a solution of methyl iodide (0.75gm, 0.0053 mol) in THF (5ml) was added to the reaction mixture while maintaining the temperature at -78 °C for 10 minutes and then stirred for 30 minutes at -78 °C.
• Aqueous hydrochloride (3.5N; 24ml) was added to a solution of tert-butyl-4- ⁇ l-[3- (difluoromethyl)- 1 -methyl- lH-pyrazole-4-sulfonyl] - 1 -fluoroethyl ⁇ piperidine- 1 - carboxylate (2.5g) in acetonitrile (lOml).
• the reaction mixture was stirred at 70°C for one hour. The progress of the reaction was monitored by gas chromatography. After completion of the reaction dichloromethane (l5ml) was added to the reaction mixture and layers were separated. The pH of aqueous layer was maintained to 12-13 using 20% NaOH (l8ml) and extracted two times with dichloromethane (25ml). The organic layer was concentrated to obtain given compound.

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