WO2014171894A1

WO2014171894A1 - Synthesis of cyclic carbonates

Info

Publication number: WO2014171894A1
Application number: PCT/SG2014/000168
Authority: WO
Inventors: Yugen Zhang; Michael R. REITHOFER; Yin Ngai SUM
Original assignee: Agency For Science, Technology And Research
Priority date: 2013-04-18
Filing date: 2014-04-17
Publication date: 2014-10-23

Abstract

The present invention provides a method of synthesizing a cyclic carbonate comprising the step of reacting an alcohol with carbon dioxide.in the presence of a base.

Description

Synthesis of Cyclic Carbonates

Technical Field The present invention generally relates to a method of synthesizing a cyclic carbonate.

Background Cyclic carbonates are versatile compounds that have useful applications as monomers for synthesis of biocompatible polymers, polar aprotic solvents, degreasers, electrolytes and as intermediates for linear dialkyl carbonate synthesis. In particular, the use of. cyclic carbonates in the production of biocompatible materials has gained increasing interest due to its . biocompatibilitv, versatility, reactivity and low cost of production.

Traditionally, cyclic carbonates have been synthesized by reacting phosgene or by coupling halogenated formates with diols . However, these methods involve the use of extremely toxic and poisonous starting materials, which are harmful to both living organisms as well as the environment.. Recently, efforts have been made to replace phosgene with the relatively less toxic triphosgene or oxalylchloride . Other novel synthetic .strategies for the synthesis of cyclic carbonates ^■ include carbon dioxide insertion into epoxides and oxetane, transesterification of diols with urea, oxidative carbonylation of diols using carbon monoxide ^■ using a transition metal catalyst and catalytic reaction from specific starting materials such as popargyl alcohols. However, all of these examples have been limited to conversion of very specific starting 'materials to very specific. products, and the reactions are not versatile such that they are applicable to a wide range of starting materials.

A simultaneous conversion of carbon dioxide and diols to cyclic carbonates would be desirable, as water would be the only by-product in the process and the reaction would be highly efficient atomicall . The use of carbon dioxide for the formation of cyclic carbonates has been successfully employed in the conversion of epoxides and oxetanes to ethylene carbonate analogues and trimethyl carbonate analogues, respectively. However, the reaction is limited to only these two precursors, and as a result, this reaction has had limited impact on the development of alternative synthetic routes of cyclic carbonates Further, this reaction is thermodynamically unfavourable, and does not proceed readily. Heterogeneous and homogeneous catalysts have been developed in an attempt to accelerate the reaction, but overall conversion of the _.diol precursors have remained low (-5%) . Further, since the limiting step for this reaction is the production of water as a by-product, dehydrating agents such as triphenylphosphine-die^'thyl azodicarboxylate, has been introduced into the reaction in an attempt to increase reaction efficiency. However, this did not result in improvement in conversion of the diol precursors or reaction efficiency.

There is therefore a need to provide a method for synthesizing a cyclic carbonate which ameliorates one or more of the disadvantages described above.

Summary

In a first aspect, there is provided a method of synthesizing a cyclic carbonate comprising the step of reacting an alcohol with carbon dioxide in the presence of a base.

9 Advantageously, the disclosed method of synthesizing a cyclic carbonate may be significantly less harmful to living organisms and the environment. More advantageously, the disclosed method may utilise green chemistry. Unlike traditional methods for synthesizing cyclic carbonates, the disclosed method may not use extremely toxic and/or poisonous starting materials. The starting materials in the disclosed method such as alcohols and carbon dioxide are non-toxic and may not require special handling. Advantageously, the disclosed method may exclude the use of chemicals that are harmful to humans. More advantageously, the disclosed method may exclude the use of cross-linking agents such as phosgene. Further advantageously, the disclosed method may not require the use of harmful inorganic catalysts. Instead, the disclosed method may use a simple, non-toxic and biocompatible base to facilitate the reaction. Even further advantageously, the disclosed method may not contribute to production of harmful by-products since the by-products of the reactions of this method are benign and nontoxic. Therefore, the disclosed method may be considerably safer both to living organisms and the environment compared to conventional routes of cyclic carbonate synthesis.

Further advantageously, the disclosed method of synthesizing a cyclic carbonate may proceed significantly more efficiently than conventional methods. The reaction may proceed in mild reaction conditions, under ambient temperature and pressure, in a variety of common and non-harmful solvents, may have a high conversion and yield and may not require high energy input for the reaction to proceed. Even further advantageously, since the reaction may proceed with high yield and limited by- products, it may be highly atomically efficient. Therefore, unlike conventional methods for synthesizing cyclic carbonates, the disclosed method may allow for efficient synthesis of cyclic carbonates from simple starting materials such as alcohols and carbon dioxide.

More, advantageously, the disclosed method of synthesizing a cyclic carbonate may be versatile and robust. Unlike traditional methods of synthesizing a cyclic carbonate, the disclosed method may not be limited in the type of starting material that may be used or the type of product that may be formed. The reaction may therefore be applicable to a wide variety of starting materials to yield a wide variety of products. Further advantageously, the disclosed method may be useful for synthesising both 5- and 6- membered cyclic carbonates, which was not possible by conventional methods.

Even more advantageously, the use of a simple, non-toxic and biocompatible base may facilitate the synthesis of a cyclic carbonate from alcohols to proceed in a_. safe, non-toxic yet efficient and versatile manner. The base may have sufficient basicity for the synthesis of cyclic carbonates, aid in the cyclization reaction and have appropriate solubility properties in solvents used for the reaction. The base may therefore play a critical role in the efficiency of the reaction.

The disclosed method for synthesizing a cyclic carbonate may be the first of its kind for synthesizing cyclic carbonates from an alcohol and carbon dioxide using a base, where the reaction is versatile and robust such that it is applicable to a wide variety of starting materials to produce a wide variety of 5- and 6-membered cyclic carbonates. Definitions

The following words and terms used herein shall have the meaning indicated:

The term "green chemistry" and "sustainable chemistry" may be used interchangeably, and refer to a philosophy of chemical research and engineering that encourages the design of products and processes that minimize the use and generation of hazardous substances. The terms "green" and "sustainable" for the purposes of this disclosure, should be construed accordingly.

The term "cyclic carbonate" refers to a non-aromatic monocyclic or multicyclic ring system containing at least one carbonare group C(=0) (0-)_·.

The term "alkyl" as a group or part of a group, refers to a straight or branched aliphatic hydrocarbon group, preferably a C₁-C₂₀ alkyl group and more preferably a Ci-^'Cio alkyl group, unless otherwise noted. Examples of suitable straight and branched Ci-C^o alkyl substituents include, but are not limited to, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl and any isomers thereof. The group may be a terminal group or a bridging group.

The term "alkanol" and "aliphatic alcohol" may be used interchangeably and refer to, as a group or part of a group, a straight or branched alkyl group comprising an alcohol (-OH) group, in which alkyl is defined herein. Preferably the alkanol group is a C1-C20 alkanol group, and more preferably a C₁-C10 alkanol group, unless otherwise noted. Examples of suitable straight and branched Ci-C₁₀ alkanol substituents include, but are not limited to, methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol and any isomers thereof. The group may be a terminal group or a bridging group .

The term "alkoxy" and "alkyloxy" may be used interchangeably and refer to, as a group or part of a group, an alkyl-0- group in which alkyl is as defined herein. The alkoxy group is preferably a Ci-C?o alkoxy group, and more preferably a Ci-Cio alkoxy group, unless otherwise noted. Examples include, but are not limited to, methoxy, ethoxy, propyloxy, butoxy, pentoxy, hexoxy, heptoxy, octoxy, nonoxy, decoxy and any isomers , thereof. The group may be a terminal group or a bridging group.

The term "aryl", as a group or part of a group, refers to an optionally substituted monocyclic, or fused polycyclic, aromatic carbocycle (ring structure having ring atoms that are all carbon) preferably having from 5-20 atoms per ring. Examples of aryl groups include phenyl, phenol, tolyl, naphthyl, anthryl and the like. The group may be a terminal group or a bridging group .

The word "substantially" does not exclude "completely" e.g. a composition which is "substantially free" from Y may be completely free from Y. Where necessary, the word "substantially" may be omitted from the definition of the invention.

Unless specified otherwise, the terms "comprising" and "comprise", and grammatical variants thereof, are intended to represent "open" or "inclusive" language such that they include recited elements but also permit inclusion of additional, unrecited elements.

As used herein, the terms "about" and "approximately", in the context of concentrations of components of the formulations, or where applicable, typically means +/- 5% of the stated value, more typically +/- 4% of the stated value, more typically +/- 3% of the stated value, more typically, +/- 2% of the stated value, even more typically +/- 1% of the stated value, and even more typically +/- 0.51 of the stated value.

Throughout this disclosure, certain embodiments may be disclosed in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the disclosed ranges. Accordingly, the description of a range should be considered to have specifically disclosed all the possible sub-ranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range .

Disclosure of Optional Embodiments

Illustrative, non-limiting embodiments of a method of synthesizing a cyclic carbonate according to the first aspect will now be disclosed.

A method of synthesizing a cyclic carbonate may comprise the step of reacting an alcohol with carbon dioxide in the presence of a base.

The cyclic carbonate may be a non-aromatic monocyclic or multicyclic ring system containing at least one carbonate group C(=0) (0-) 2· The cyclic carbonate may have 5 to 8 atoms per ring. The cyclic carbonate may have 5, 6, 7 or 8 atoms per ring. The cyclic carbonate may be a 5-membered, 6-membered, 7-membered or β-membered heterocyclic ring. The cyclic carbonate may be a 5-membered or 6-membered heterocyclic ring.

The cyclic carbonate may have the general formula (I) :

(I)

'n' in formula (I) may be 0, 1, 2 or 3. ^vn' in formula (I) may be 0 or 1. R¹, R', R³, R⁴, R⁵ or R⁶ is independently selected from the group consisting of H, optionally substituted C i-i - alkyl, optionally substituted Ci-io-alkanol and optionally substituted C5-2o~aryl.

R¹ or R⁴ in formula (I) may be independently selected from the group consisting of H, Ci-5-al kanol , Cs-io-aryl and Ci-^-alkyl. R¹ or R⁴ in formula (I) may be independently selected from the group consisting of H, methanol, ethanol, n-propanol, 2- propanol, n-butanol, sec-butanol, iso-butanol, tert-butanol , n- pentanol, 2-pentanol, 3-pentanol 3-methylbutan- l-ol , 2- methylbutan-l-ol , 2, 2-dimethylpropan-l-ol , 3-methylbutan-2-ol , 2-methylbutan-2-ol, phenyl, o-phenol, p-phenol, m-phenol, o- tolyl, p-tolyl, m-tolyl, naphthyl, anthryl, methyl, ethyl, n- propyl, 2-propyl, n-butyl, sec-butyl, iso-butyl, tert-butyl, n- pentyl, 3-methyl-l-butyi, 2-methyl-l-butyl , 2 , 2 , -dimethyl- 1- propyl, 3-pentyl, 2-pentyl, 3-methyl - 2-butyl and 2-methyl-2- butyl. R or R in formula (I) may be independently selected from the group consisting of H, methanol, phenyl and methyl.

R~ or R⁵ in formula (I) may be independently selected from the group consisting of .H, Ci_ 5-alkyl and C₅_i₀-aryl. R" or R⁵ formula (I) may be independently selected from the group consisting of H, methyl, ethyl, n-propyl, 2-propyl, n-butyl, sec-butyl, iso-butyl, tert-butyl, n-pentyl, 3-methyl-l-butyl, 2- methyl- 1-butyl , 2, 2, -dimethyl-l-propyl, 3-pentyl, 2-pentyl, 3- methyl-2-butyl and 2-methyl-2-butyl , phenyl, o-phenol, p-phenol, , m-phenol, o-tolyl, p-tolyl, m-tolyl, naphthyl and anthryl. R² or R⁵ in formula (I) may be independently selected from the group consisting of H, ethyl and phenyl .

R³ or R⁶ in formula (I) may be independently selected from the group consisting of H and Ci-s-alkyi . R³ or R⁶ in formula (I) may be independently selected from the group consisting of H, methyl, ethyl, n-propyl, 2-propyl, n-butyl, sec-butyl, iso-butyl, tert-butyl, n-pentyl, 3-methyl-l-butyl, 2-methyl- 1-butyl , 2,2,- dimethyl-l-propyl , 3-pentyl, 2-pentyl, 3-methyl-2-butyl and 2- methyl-2-butyl . R³ or R^b in formula (I) may be independently selected from the group consisting of H and methyl.

The alcohol may have the formula (II) :

ormula (II) may or 3. in formula may be 0 or 1. R , R-, R^J, R R⁵ or ^"R° in formula (II) may independently selected from the group consisting of H, optionally substituted Ci-io-alkyl, optionally substituted Ci-io- alkanol and optionally substituted C5-2o-aryl.

R¹ or R⁴ in formula (II) may be independently selected from the group consisting of H, Ci-5-alkanol , Cs-io-aryl and Ci-5-alkyl. R¹ or in formula (II) may be independently selected from the group consisting of H, methanol, ethanol, n-propanol, 2- propanol, n-butanol, sec-butanol, iso-butanol, tert-butanol , n- pentanol, 2-pentanol, 3-pentanol 3-methylbutan-l-ol, 2- methylbutan- l-ol , 2, 2-dimethylpropan-l-ol, 3-methylbutan-2-ol , 2-methylbutan-2-ol , phenyl, o-phenol, p-phenol, m-phenol, o- tolyl, p-tolyl, m-tolyl, naphthyl, anthryl, methyl, ethyl, n- propyl, 2-propyl, n-butyl, sec-butyl, iso-butyl, tert-butyl, n- pentyl, 3-methyl-l-butyl , 2-methyl- 1-butyl , 2 , 2 , -dimethyl-1- propyl, 3-pentyl, 2-pentyl, 3-inethyl-2-butyl and 2-methyl-2- butyl. R¹ or R⁴ - in formula (II) may be independently selected from the group consisting of H, methanol, phenyl and methyl.

R² or R⁵ in formula (II) may be independently selected from the group consisting of H, Ci-5-alkyl and Cs-io-aryl. R² or R⁵ in ■ formula (II) may be independently selected from the group consisting of H, methyl, ethyl, n-propyl, 2-propyl, n-butyl, sec-butyl, iso-butyl, tert-butyl, n-pentyl, 3-methyl-l-butyl, 2- methyl- 1-butyl , 2, 2, -dimethyl - 1-propyl , 3-pentyl, 2-pentyl, 3- methyl-2-butyl , 2-methyl-2-butyl, phenyl, o-phenol, p-phenol, m- phenol, o-tolyl, p-tolyl, m-tolyl, naphthyl and anthryl.^' R² or R⁵ in formula (II) may be independently selected from the group consisting of K, ethyl and phenyl.

R³ or R⁶ in formula (II) may be independently selected from the group ^' consisting of H and -Ci-5-alkyl . R³ or R^ in formula (II) may be independently selected from the group consisting of H, methyl, ethyl, n-propyl, 2-propyl, n-butyl, sec-butyl, iso-butyl, tert-butyl, n-pentyl, methyl, ethyl, n-propyl, 2-propyl, n-butyl, sec-butyl, iso-butyl, ter-butyl, n-pentyl, 3-methyl-l-butyl, 2- methyl-l-butyl, 2, 2, -dimethyl-l-propyl, 3-pentyl, 2-pentyl, 3- methyl-2-butyl and 2-methyl-2-butyl . R³ or R° in formula (II) may be independently selected from the group consisting of H and methyl .

X in formula (II) may be a leaving group selected^' from halo, R⁷-S0₃-* , or R⁸-S0₄-* . The halo group may be selected from the group consisting of fluoro, chloro, bromo and iodo.

R⁷ in X may be selected from the group consisting of hydrogen, optionally substituted Ci_io-alkoxy , optionally substituted Ci-io-alkyl, optionally substituted Ci-io-trihalo and optionally substituted C₅_io-aryl. R⁷ in X may be selected from the group consisting of hydrogen, methoxy, ethoxy, n-propoxy, 2- propoxy, n-butoxy, sec-butoxy, iso-butoxy, tert-butoxy, n- pentoxy, 2-pentoxy, 3-pentoxy, 3-methyl-l-butoxy, ^' 2-methyl-l- butoxy, 2, 2-dimethyl-l-propoxy, 3-methyl-2-butoxy , 2-methyl-2-^' butoxy, methyl, ethyl, n-propyl, 2-propyl, n-butyl, · sec-butyl, iso-butyl, ter-butyl, n-pentyl, 3-methyl-l-butyl, 2-methyl-l- butyl, 2 , 2 , -dimethyl-l-propyl , 3-pentyl, 2-pentyl, 3-methyl-2- butyl, 2-methyl-2-butyl , trifluoromethyl, 1, 1, 1-trifuloroethyl , 3,3, 3-trifluoropropyl, 4,4, 4 -trifluorobutyl, 3, 3, 3-trifluoro-l- methylpropyl , 3,3, 3-trifluoro-2-methylpropyl , 2,2,2-trifluoro- 1 , 1-dimethylethyl, 5 , 5 , 5-trifluoropentyl , 4 , , -trifluoro-3- methylbutyl, 4 , 4 , 4-trifluoro-2-methylbutyl , 3, 3, 3-trifluoro-2- propyl, 3, 3, 3-trifluoro-2-methylpropyl, trichloromethyl , 1,1,1- trichloroethyl , 3 , 3 , 3-trichloropropyl , 4 , 4 , 4 -trichlorobutyl , 3, 3, 3-trichloro- 1-methylpropyl , 3, 3, 3-trichloro-2-methylpropyl , 2, 2, 2-trichloro-l, 1-dimethylethyl, 5 , 5 , 5-trichloropentyl , 4,4,4- trichloro-3-methylbutyl, 4 , 4 , 4-trichloro-2-methylbutyl , 3,3,3- trichloro-2-propyl , 3, 3, 3-trichloro-2-methylpropyl, tribromomethyl, 1 , 1 , 1-tribromoethyl , 3 , 3 , 3-tribromopropyl ,

4 , 4 , 4-tribromobutyl , 3 , 3 , 3-tribromo-l-methylpropyl , 3,3,3- tribromo-2-methylpropyl, 2,2, 2-tribromo-l , 1-dimethylethyl ,

5, 5, 5-tribromopentyl, 4 , 4 , 4 - tribromo-3-methyibutyl , 4,4,4- tribromo-2-methylbutyl , 3 , 3 , 3-tribromo-2-propyl , 3 , 3 , 3-tribromo- 2-methylpropyl, triiodomethyl , 1, 1, 1-triiodoethyl, 3,3,3- triiodopropyl , 4,4, 4-triiodobutyl , 3,3, 3-triiodo-l-methylpropyl , 3,3, 3-triiodo-2-methylpropyl , 2,2, 2-triiodo-l, 1-dimethylethyl, 5,5, 5-triiodopentyl , 4,4, 4-triiodo-3-methylbutyl , 4,4, 4 -trioodo- 2-methylbutyl , 3 , 3 , 3-triiodo-2-propyl , 3, 3, 3-triiodo-2- methylpropyl , phenyl, o-phenol, p-phenol, m-phenol, o-tolyl, p- tolyl, m-tolyl, naphthyl, anthryl, n-hexoxy, n-heptoxy, n-octoxy, n-nonoxy, n-decoxy, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, and any isomers thereof. R⁷ in X -may be selected from the group consisting of hydrogen, methoxy, methyl, trifluoromethyl , p- tolyl and o-tolyl.

R⁸ in X is selected from the group consisting of hydrogen, optionally substituted Ci-₁₀-alkyl , optionally substituted Ci-io- trihalo and optionally substituted C₅-i₀-aryl. R⁷ in X may be selected from the group consisting of hydrogen, methyl, ethyl, n-propyl, 2-propyl, n-butyl, sec-butyl, iso-butyl, ter-butyl, n- pentyl, 3-methyl-l-butyl, 2-methyl-l-butyl, 2 , 2 , -dimethyl- 1- propyl, 3-pentyl, 2-pentyl, 3-methyl-2-butyl , 2-methyl-2-butyl , trifluoromethyl , 1, 1, 1-trifuloroethyl, 3, 3, 3-trifluoropropyl , 4 , 4 , -trifluorobutyl , 3, 3, 3-trifluoro-l-methylpropyl, 3,3,3- trifluoro-2-methylpropyl, 2, 2, 2-trifluoro-1, 1-dimethylethyl,

5, 5, 5-trifluoropentyl, , 4 , -trifluoro-3-methylbutyl , 4,4,4- trifluoro-2-methylbutyl , 3, 3, 3-trifluoro-2-propyl, 3,3,3- trifluoro-2-methylpropyl , trichloromethyl , 1,1, 1-trichloroethyl , 3 , 3 , 3-trichloropropyl , 4 , 4 , 4 -trichlorobutyl , 3 , 3 , 3-1 richloro- 1 - methylpropyl , 3,3, 3-1 richloro- 2-methylpropyl, 2,2,2-trichloro- 1 , 1-dimethylethyl , 5 , 5 , 5- trichloropentyl , 4 , 4 , 4-trichloro-3- methylbutyl, 4 , , -trichloro-2-methylbutyl , 3 , 3 , 3-trichloro-2- propyl, 3, 3, 3-trichloro-2-methylpropyl, tribromomethyl , 1,1,1- tribromoethyl , 3 , 3 , 3-tribromopropyl , 4 , 4 , 4-tribromobutyl, 3,3,3- tribromo-1-methylpropyl , 3, 3, 3-tribromo-2-methylpropyl, 2,2,2- tribromo-1, 1-dimethylethyl, 5 , 5 , 5-tribromopentyl , 4,4,4- tribromo-3-methylbutyl , 4,4, 4-t ribromo-2-methylbutyl , 3,3,3- tribromo-2-propyl , 3, 3, 3-tribromo-2-methylpropyl , triiodomethyl,

1.1.1- t riiodoethyl , 3 , 3 , 3-triiodopropyl , 4 , 4 , 4 -triiodobutyl , 3, 3, 3-triiodo-l-methylpropyl, 3 , 3 , 3- triiodo-2-methylpropyl ,

2.2.2-triiodo-l , 1-dimethylethyl , 5, 5, 5-triiodopentyl, 4,4,4- triiodo-3-methylbutyl , 4 , 4 , 4-trioodo-2-methylbutyl, 3,3,3- triiodo-2-propyl, 3 , 3 , 3-triiodo-2-methylpropyl , phenyl, ο- phenol, p-phenol, m-phenol, o-tolyl, p-tolyl, m-tolyl, p-tolyl, m-tolyl, o-tolyl, naphthyi, anthryl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, and any isomers thereof. R⁸ in X may be selected from the group consisting of hydrogen, methyl, trifluoromethyl, p-tolyl and o-tolyl.

The asterisk in X may denote the point of attachment of X to the rest of the compound.

X may be selected from the group consisting of chloro, bromo, iodo,

O

CH,0 S 0— CH, S 0-

O (methyl sulphat (mesylate) ,

Jtriflate) , toluenesulfonyl ) ,

The alcohol may be a diol.

The method of synthesizing the cyclic carbonate may comprise the step of replacing one hydroxyl functional group of the diol with a leaving group. The leaving group may be selected from the group consisting of halo, R⁷-S0₃-* and R⁸-S0₄-⁺ . The halo group may be selected from the group -consisting of fluoro, chioro, bromo and iodo.

P.⁷ of the leaving group may be selected from the group consisting of hydrogen, optionally substituted Ci-io-alkoxy, optionally substituted Ci-io-alkyl , optionally substituted Ci-i₀- trihalo and optionally substituted Cs-io-aryl. R⁷ of the leaving group may be selected from the group consisting of hydrogen, methoxy, ethoxy, n-propoxy, 2-propoxy, n-butoxy, sec-butoxy, iso-butoxy, tert-butoxy, n-pentoxy, 2-pentoxy, 3-pentoxy, 3- methyl-l-butoxy, 2-methyl-l-butoxy, 2 , 2-dimethyl-l-propoxy , 3- methyl-2-butoxy , 2-methyl-2-butoxy, methyl, ethyl, n-propyl, 2-- propyi, n-butyl, sec-butyl, iso-butyl, ter-butyl, n-pentyl, 3- methyl- 1-butyl , 2-methyl- 1-butyl , 2 , 2 , -dimethyl-l-propyl , 3- pentyl, 2-pentyl, 3-methyl-2-butyl , 2-methyl-2-butyl , trifluoromethyl , 1, 1, 1-trifuloroethyl, 3, 3, 3-trifluoropropyl,

4.4.4-trifluorobutyl, 3,3, 3-trifluoro-l-methylpropyl, 3,3,3- t ri fluoro-2-methylpropyl , 2,2,2-trifluoro-l, 1 -dimethylethyl ,

5.5.5-trifluoropentyl , 4 , , 4-trifluoro- 3-methylbutyl , 4,4,4- trifluoro-2-methylbutyl , 3, 3, 3-trifluoro-2-propyl, 3,3,3- trifluoro-2-methylpropyl , trichloromethyl , 1, 1, 1-trichloroethyl, 3,3,3-trichloropropyl, 4,4, 4-t richlorobutyl , 3,3,3-trichloro-l- methylpropyl , 3 , 3 , 3-trichloro-2-methylpropyl , 2 , 2 , 2-trichloro- 1 , 1-dimethylethyl , 5 , 5 , 5-trichloropentyl , , 4 , 4-trichloro-3- methylbutyl, , 4 , 4 -trichloro-2-methylbutyl , 3 , 3 , 3- trichloro-2- propyl, 3 , 3 , 3-trichloro-2-methylpropyl , tribromomethyl , 1,1,1- tribromoethyl , 3 , 3 , 3-t ribromopropyl , 4 , 4 , -tribromobutyl , 3,3,3- tribromo-l-methylpropyl , 3,3, 3-t ribromo-2-methylpropyl , 2,2,2- tribromo- 1 , 1-dimethylethyl , 5 , 5 , 5- tribromopentyl , 4,4,4- tribromo- 3-methylbutyl , 4 , 4 , 4 -t ribromo-2-methylbutyl , 3,3,3- tribromo-2-propyl, 3, 3, 3-tribromo-2-methylpropyl , triiodomethyl ,

1.1.1-triiodoethyl , 3 , 3 , 3- t iiodopropyl , 4 , , 4- riiodobutyl , 3, 3, 3-triiodo-l-methylpropyl, 3, 3, 3-triiodo-2-methylpropyl ,

2.2.2-triiodo-l , 1-dimethylethyl , 5 , 5 , 5-triiodopentyl , 4,4,4- triiodo-3-methylbutyl, , 4 , 4-trioodo-2-methylbutyl, 3,3,3- triiodo-2-propyl , 3 , 3 , 3-triiodo-2-methylpropyl , . phenyl, o- phenol, p-phenol, m-phenol, o-tolyl, p-tolyl, m-tolyl, o-tolyl, p-tolyl, m-tolyl, naphthyl, anthryl, n-hexoxy, n-heptoxy, n- octoxy, n-nonoxy, n-decoxy, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, and any isomers thereof. R⁷ of the leaving group may be selected from the group consisting of hydrogen, methoxy, methyl, trifluoromethyl, p-tolyl and o-tolyl.

R⁸ of the leaving group is selected from the group consisting of hydrogen, optionally substituted Ci_io^~alkyl, optionally substituted Ci-io-trihalo and optionally substituted Cs-io-aryl. R⁸ of the leaving group may be selected from the group consisting of hydrogen, methoxy, ethoxy, n-propoxy, 2-propoxy, n-butoxy, sec-butoxy, iso-butoxy, tert-butoxy, n-pentoxy, 2- pentoxy, 3-pentoxy, 3-methyl-l-butoxy , 2-methyl-l-butoxy , 2,2- dimethyl-l-propoxy , 3-methyl-2-butoxy , 2-methyl-2-butoxy , methyl, ethyl, n-propyl, 2-propyl, n-butyl, sec-butyl, iso-butyl, ter- butyl, n-pentyl, 3-methyl-l-butyl , 2-methyl-l-butyl , 2,2,- dimethyl-l-propyl, 3-pentyl, 2-pentyl, 3-methyl-2-butyl , 2- methyl-2-butyl , trifluoromethyl , 1 , 1 , 1 -1 ri fuloroethyl , 3,3,3- trifluoropropyl, 4 , 4 , 4-trifluorobutyl, 3, 3, 3-trifluoro-1- methylpropyl , 3 , 3 , 3-trifluoro-2-methylpropyl , 2 , 2 , 2-trifluoro- 1 , 1-dimethylethyl , 5, 5, 5-trifluoropentvl, 4 , 4 , 4-trifluoro-3- methylbutyl , 4,4, 4-trifluoro-2-methylbutyl , 3,3,3-trifluoro-2- propyl, 3, 3, 3-trifluoro-2-methylpropyl, trichloromethyl , 1,1,1- trichloroethyl , 3, 3, 3-trichloropropyl, , 4 , -trichlorobutyl , 3, 3, 3-trichloro-l-methylpropyl, 3, 3, 3-trichloro-2-methylpropyl , 2,2,2-trichloro-l, 1-dimethylethyl , 5,5, 5-trichloropentyl , 4,4,4- trichloro-3-methylbutyl , 4,4, 4 - 1 richloro-2-methylbut yl , 3,3,3- trichloro-2-propyl , 3, 3, 3-trichloro-2-methylpropyl , tribromomethyl , 1 , 1 , 1-tribromoethyl , 3 , 3 , 3-tribromopropyl , 4 , , 4-tribromobutyl , 3 , 3 , 3 -tribromo- 1-methylpropyl , 3,3,3- tribromo- 2 -methylpropyl , 2,2, 2-tr ibromo- 1 , 1-dimethylethyl , 5 , 5 , 5-tribromopentyl , 4 , 4 , -tribromo-3-methylbutyl , 4,4,4- tribromo-2-methylbutyl , 3, 3, 3- tribromo-2-propyl , 3, 3, 3-tribromo- 2-methylpropyl , triiodomethyl , 1 , 1 , 1 -1 riiodoethyl , 3,3,3- triiodopropyl , 4,4, 4-triiodobutyl , 3,3, 3-triiodo- 1 -methylpropyl , 3,3, 3-triiodo-2 -methylpropyl , 2,2,2-triiodo-l, 1 -dimethyl ethyl , 5,5, 5-triiodopentyl , 4,4, 4-triiodo- 3-methylbutyl , 4,4, 4-trioodo- 2-methylbutyl , 3 , 3 , 3-triiodo-2-propyl , 3 , 3 , 3-triiodo-2- methylpropyl , phenyl, o-phenol, p-phenol, m-phenol, o-tolyl, p- tolyl, m-tolyl, p-tolyl, m-tolyl, o-tolyl, naphthyl, anthryl, n- hexoxy, n-heptoxy, n-octoxy, n-nonoxy, n-decoxy, n-hexyl, n- heptyl, n-octyl, n-nonyl, n-decyl, and any isomers thereof. R⁸ of the leaving group may be selected from the group consisting of hydrogen, methoxy, methyl, trifluoromethyl , ρ-tolyl and o-tolyl.

The asterisk of the leaving group may denote the point of attachment of the leaving group to the rest of the compound.

The leaving group may be selected from the group consisting of chloro, bromo, iodo,

(mesylate)

O ;triflate) , (p-toluenesulfonyl ) ,

The replacing step of one hydroxyl functional group of the diol with a leaving group may comprise the step of reacting the diol with a halide selected from phosphorus trihalide or thionylhalide .

The halide may be selected from the group consisting of phosphorus trichloride, phosphorus tribromide, phosphorus triiodide, thionyl chloride and thionyl bromide.

The replacing step of one hydroxyl functional group of the diol with a leaving group may comprise the step of reacting the diol with a sulfonyl halide selected from R⁹-0-SO:-X¹ or R⁹-SO_:-X¹. X¹ may be selected from chloride or bromide and R⁹ may be selected from C₅_₂o-aryl or Ci-io-alkyl . R⁹ may be selected from the group consisting of phenyl, o-phenol, p-phenol, m-phenol, o- tolyl, p-tolyl, m-tolyl, p-tolyl, m-tolyl, o-tolyl, naphthyl, anthryl, methyl, ethyl, n-propyl, 2-propyl, n-butyl,. sec-butyl, iso-butyl, ter-butyl, n-pentyl, 3-methyl-l-butyl , 2-methyl-l- butyl, 2 , 2 , -dimethyl-l-propyl , 3-pentyl, 2-pentyl, 3-methyl-2~ butyl, 2-methyl-2-butyl , n-hexoxy, n-heptoxy, n-octoxy, n-nonoxy, n-decoxy, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, and any isomers thereof.

The replacing step may further comprise an organic base selected from an N containing heteroaryl. The N containing heteroaryl may be selected from the group consisting of benzimidazole , benzisoxazole, benzothiazole , benzoxazole, cinnoline, diazine, dithiazole, furazan, imidazole, melamine, oxazine, oxazole, isoxazole, oxadiazole, pyrazine, pyrazole, pyridine, pyrimidme, pyrrole, qumazoline, triazine, tetrazine, tetrazole, thiazine, thiazole, thiadiazole and isothiazole, azepine, diazepine, thiazepine and azocine.

The method of synthesizing the cyclic carbonate may comprise the step of reacting an alcohol with carbon dioxide in the presence of a base. The base may be a deprotonating agent.

The base may be soluble in solvents. The base may be soluble in aqueous solvents. The base may be soluble in organic solvents. .The base may be soluble in D F, DMSO or a mixture thereof .

The base may be an inorganic base. The base may be ammonia and salts thereof. The base may be ammonium hydroxide. The base may be a -salt of carbonate or hydroxide. The base may be a carbonate salt. The base may be a metal salt of a carbonate. The base may be selected from alkali metal carbonate or alkaline earth metal carbonate. The base may be selected from the group consisting of lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, caesium carbonate, beryllium carbonate, strontium carbonate, magnesium carbonate and calcium carbonate. The base may be caesium carbonate.

The caesium carbonate may be a sufficiently strong base to cause the deprotonation of alcohols to form alkoxides. The caesium carbonate may have an appropriate p¾ for deprotonating an alcohol to form the corresponding alkoxide. Caesium carbonate may be soluble in DMF, DMSO or a mixture thereof. Caesium carbonate may aid in ring-closure reactions. Caesium carbonate may aid in an intramolecular anionic SNo substitution to cause the ring-closure reaction. The caesium carbonate may be a suitable base for the synthesis of cyclic carbonates.

The method of synthesizing the cyclic carbonate may comprise reacting the base with the alcohol at a baseralcohol ratio in the range of about 0.8:1 to about 1.8:1, about 0.8:1 to about 1:1, about 0.8:1 to about 1.2:1, about 0.8:1 to about 1.4:1, about 0.8:1 to about 1.6:1, about 1:1 to about 1.2:1, about 1:1 to about 1.4:1, about 1:1 to about 1.6:1, about 1:1 to about 1.8:1, about 1.2:1 to about 1.4:1, about 1.2:1 to about 1.6:1, about 1.2:1 to about 1.8:1, about 1.4.:1 to about 1.6:1, about 1.4:1 to about 1.8:1 or about 1.6:1 to about 1.8:1. The method of synthesizing a cyclic carbonate may comprise reacting the base with the alcohol at a base:alcohol ratio in the range of about 1:1 to about 1.5:1.

The step of reacting the base with the alcohol may be undertaken at a temperature in the range of about 25 °C to about 55 °C, about 25 °C to about 30 °C, about 25 °C to about 35 °C, about 25 °C to about 40 °C, about 25 °C to about 45 °C, about 25 °C to about 50 °C, about 30 °C to about 35 °C, about 30 °C to about 40 °C, about 30 °C to about 45 °C, about 30 °C to about 50 °C, about 30 °C to about 55 °C, about 35 °C to about 40 °C, about 35 °C to about 45 °C, about 35 °C to about 50 °C, about 35 °C to about 55 °C, about 40 °C to about 45 °C, about 40 °C to about 50 °C, about 40 °C to about 55 °C, about 45 °C to about 50 °C, about 45 °C to about 55 °C or about 50 °C to about 55 °C . The step of reacting the base with the alcohol may be undertaken at a temperature in the range of about 30 °C to about 50 °C .

The method of synthesizing the cyclic carbonate may comprise the step of reacting an alcohol with carbon dioxide in the presence of a base. The carbon dioxide may be at a pressure in the range of about 0.25 atm to about 12 atm, about 0.25 atm to about 0.5 atm, about 0.25 atm to about 1 atm, about 0.25 atm to about 2 atm, about 0.25 atm to about 5 atm, about 0.25 atm to about 7.5 atm, about 0.25 atm to about 10 atm, about 0.5 atm to about 1 atm, about 0.5 atm to about 2 atm, about 0.5 atm to about 5 atm, about 0.5 atm to about 7.5 atm, about 1 atm to about 2 atm, about 1 atm to about 5 atm, about 1 atm to about 7.5 atm, about 1 atm to about 10 atm, about 1 atm to about 12 atm, about 2 atm to about 5 atm, about 2 atm to about 7.5 atm, about 2 atm to about 10 atm, about 2 atm to about 12 atm, about 5 atm to about 7.5 atm, about 5 atm to about 10 atm, about 5 atm to about 12 atm, about 7.5 atm to about 10 atm, about 7.5 atm to about 12 atm or about 10 atm to about 12 atm. The carbon dioxide may be at a pressure in the range of about 0.5 atm to about 10 atm . The step of reacting the base with the alcohol may be undertaken for a time period in the range of about 1 to about 30 hours, about 1 to about 5 hours, about 1 to about 10 hours, about 1 to about 15 hours, about 1 to about 20 hours, about 1 to about 25 hours, about 5 hours to about 10 hours, about 5 hours to about 15 hours, about 5 hours to about 20 hours, about 5 hours to about 25 hours, about 5 hours to about 30 hours, about 10 to about 15 hours, .about 10 to about 20 hours, about 10 to about 25 hours, about 10 hours to about 30 hours, about 15 to about 20 hours, about 15 to about 25 hours, about 15 hours to about 30 hours, about 20 to about 25 hours, about 20 hours to about 30 hours or about 25 hours to about 30 hours.

The method of synthesizing the cyclic carbonate may comprise a step of adding a solvent. The solvent may be added to dissolve the alcohol. The solvent may be an organic solvent. The organic solvent may be a polar aprotic solvent. The polar aprotic solvent may be selected from the group consisting of dimethyl formamide (DMF), dimethyl sulfoxide . (DMSO) , tetrahydrofuran (THF) , ethyl acetate (EtOAc), acetone, acetonitrile (MeCN) , hexamethylphosphoramide (HMPA) and dichloromethane . The polar aprotic solvent may be dimethyl formamide (DMF) or dimethyl sulfoxide (DMSO) .

The cyclic carbonate may be synthesized at a yield more than 50%, more than 60%, more than 70%, more than 80%, more than 90% or more than 95% .

Examples

Non-limiting examples of the invention will be further described in greater detail by reference to specific Examples, which should not be construed as in any way limiting the scope of the invention.

Example 1 : Experimental details All reactions were set up in an Innovative Technologies

Glovebox equipped with nitrogen gas. Chemicals were purchased from commercial sources and used as received without further purification. Anhydrous solvents were purchased in Sure-seal packaging from Sigma-Aldrich and were used as received. Carbon dioxide gas was supplied by SOXAL. ¹H and ^ljC NMP. spectroscopy was performed on a Bruker AV-400 (400 MHz) instrument. Reaction temperatures refer to temperatures of the heating blocks. With the exception of compound 7, all cyclic carbonates described below have been previously prepared by other methods and characterized by NMR spectroscopy. Standard reaction conditions

The general reaction procedures were as follows. In a nitrogen filled glove box, a 20 mL crimp top vial was charged with 1 mmol starting material and dissolved in 3 mL N,N- dimethylformamide (DMF) . Subsequently, 1.1^' mmol (1.1 equiv.) CS2CO3 was added at once. The vial was closed with a crimp cap, brought out of the glove box and carbon dioxide was bubbled through the solution for about 1 minute. The vial was placed in a 40 °C heat block and stirred for 15 hours under 1 atm of carbon dioxide using a carbon dioxide filled balloon. The reaction was quenched by adding 15 mL dichloromethane (DCM) . The resulting suspension was filtered over Celite, and the solvent was first removed on a rotary evaporator. The DMF was removed on an oil vacuum pump over 6 hours, then the residue was resuspended in^' DCM and filtered over cotton wool to remove any^' traces of salts. The solvent was removed and the product was dried on an oil vacuum pump.

Example 2 : Investigating the use of halo-alcohols

To assess the possibility of synthesising cyclic carbonates using green chemistry and without the use of a transition metal catalyst, the^' use of general halo-alcohols as starting materials was investigated. The major challenge to overcome was that the reaction may produce a large amount of .polycarbonates with low selectivity towards the cyclic carbonate products. Using the reaction conditions outlined in Example 1, a test reaction was carried out with 3-chloro- 1-propanol and carbon dioxide in the presence of K-CO₃ and a catalytic amount of triazabicyclodecene (TBD) (Scheme. 1) . At 60 °C, trimethyl carbonate (TMC, compound 1) could be detected in 58 % yield by NMP. spectroscopy, whereas a small decrease in yield was observed when the reaction was carried out at 40 °C.

3-chl

t

(Compound 1)

Scheme 1 shows the conversion of 3-chloro-l-propanol trimethyl carbonate (TMC) in the presence of tiazabicyclodec (TBD) .

Interestingly, only minor polymeric by-products of compound 1 were observed even though TBD was used as an additive. It should be noted that even sparteine, a weaker base than TBD, is capable of polymerizing TMC (compound 1) within minutes. The fact that TBD did not cause a polymerization of compound 1 may be explained by the carbon dioxide present in the reaction binding to TBD and acting as an inhibitor of the polymerization reaction.

This was the first example showing that a 6-membered cyclic carbonate can be synthesized directly from carbon dioxide without using any toxic starting materials such as phosgene or carbon monoxide. Example 3 : Investigating the influence of various reaction conditions

The influence of altering the various reaction conditions was investigated using the reaction of Example 2.

Influence of the base

As shown in Table 1, an increase in the yield of compound 1 was observed when 2CO3 was replaced with Cs C0₃. At 60 °C, compound 1 was formed with up to 77 % yield by NMR spectroscopy, whereas almost quantitative formation of compound 1 was detected by lowering the temperature to 40 °C. However, employing the stronger base KO^tBu resulted in a significant decrease in yield and only 20 % of compound 1 could be detected by NMR spectroscopy .

Table 1. Influence of the base towards TMC (compound 1)

formation

Entry Base rrc yield/%^w

J Cs₂C0₃ 60 77

4 Cs₂C0₃ 40 95

5 ^' KO'Bu 40 20

Yield was determined by ¹ H-NMR using mesitylens as internal standard.

It is believed that the cesium carbonate is most effective base for this reaction, as it is a sufficiently strong base to cause the deprotonation of alcohols to form alkoxides. K2CO₃ is not a strong enough base to cause the deprotonation, while KO^tBr is too strong a base, making it too sensitive to reaction conditions and difficult to handle. Further, C S 2CO 3 is readily available in organic solvents such as DMF, whereas other carbonate salts such as K2CO3 is not as soluble. This may also contribute to the efficacy of C S 2CO 3 as a base for this reaction.

For a successful reaction, it was found that at least 1 equivalent of base was required. Influence of a catalyst

The influence of a catalyst on the reaction^' was investigated by replacing TBD with an imidacolium catalyst to activate carbon dioxide. When 1 , 3- (2 , 6-diisopropylphenyl ) - imidazolium (IPr) was used, no change in yield was observed. However, the use of 1 , 3- ( 2 , 6-dimethylphenyl ) -imidazolium (SMes) resulted in a slight decrease in yield (92 %) . Since only minor changes in yield were observed with different catalysts, but large changes of product formation was observed with different bases (as discussed in detail above in "Influence of the base"), the role of the catalyst in the reaction was further investigated .

When the reaction was performed under standard conditions (40 °C, 1 atm carbon dioxide, 1.1 eq . Cs:C0₃, 15 hour reaction time) both in the presence and absence of the TBD catalyst, the yield by NMR spectroscopy did not change (95%) . Therefore, it was concluded that the addition of a catalyst for the activation of carbon dioxide was not required to form TMC (compound 1) . Further, in order to prove that C S 2CO 3 was not acting as a catalyst, a sub-stoichiometric amount of CS2CO3 was used in a reaction. Full conversion of the starting material was not observed and the yield of compound 1 correlated with the amount of Cs₂C0₃ used. This showed that CS CO 3 was not acting as a catalyst in this reaction.

Influence of carbon dioxide In order to show that the carbon dioxide is essential for the reaction, the experiment was carried out in the absence of carbon dioxide. As expected, formation of compound 1 could not be observed under the standard reaction conditions of Example 2 without carbon dioxide.

Influence of the solvent

Reactions proceeded most successfully when DMF or DMSO was used as the solvent. Reactions performed in polar volatile solvents such as water, THF and acetonitrile were unsuccessful, as no product formation was observed.

Influence of the reaction temperature ' The reaction proceeded successfully in the temperature range of 30 °C to 50 °C. Although the reaction also proceeded at temperatures above 60 °C, the yield and purity of the reaction was decreased. Summary

Based on the above results, the reaction mechanism for the reaction of Example 2 was postulated to be as described in Scheme 2. In the initial step, C S 2CO 3 deprotonates the alcohol, resulting in the formation of caesium alkoxide, which subsequently reacts with carbon dioxide to form a carbonate. In the final step, TMC (compound 1) is formed by an intermolecular ring closing reaction, yielding CsCl as a by-product.

CsHC0₃ CsCl

Schem 2 shows the proposed reaction mechanism for the formation of TMC using 3-chloro-l-propanol as a starting material and CS CO3 as a base.

Example 4 : Investigating the versatility of the reaction based on different starting materials

The versatility of the reaction and its applicability to various starting materials was investigated.

Influence of the leaving group

Based on the reaction of Example 2, the effect of changing the chloride leaving ■ group to other halide groups was investigated. When 2-bromo- 1-ethanol and 2-iodo- 1-ethnaol were used as the starting material, compound 2 was obtained, as expected, at a 92 % yield based on NMR spectroscopy.

Since the accessibility of the halide alcohol is limited, the possibility of using a sulfonate group such as a tosylate group as a leaving group was also explored.

Tosylate

Tosylates are easily accessible by reaction of tosyl chloride with the respective alcohol in the presence of a base, hence this synthetic strategy was expected to allow the conversion of diols into cyclic carbonates in two reaction steps. ^'Reaction of 2-tosyl-l-ethanol with carbon dioxide in the presence of 1.1 equivalents of CS2CO3 in DMF yielded ethylene carbonate in comparable yield to, the product obtained from 2- bromo-l-ethanol .

Other possible leaving groups that may perform in a similar manner to tosylate groups include methyl sulphate, mesylate, and triflate.

Meth}'l sulfate

Selectivity for ring sizes

The selectivity of the reaction to form 5-membered rings over 6-membered rings was investigated- using (±) -3-chloro-l, 2- propanediol. After 15 hours of reaction time, (±) -3-chloro-l , 2- propanediol was converted exclusively to glyceryl carbonate (Table 2, compound 3) . The exclusive formation of the 5-membered ring demonstrated the high selectivity of the reaction to yield the more thermodynamically stable compound.

To further investigate the selectivity of the reaction, the possibility of forming 7- and 8-membered rings was also investigated. When -chlorobutan-l-ol was reacted with carbon dioxide in the presence of 1.1 equivalents of CS2CO₃ in DMF, no product formation was observed by ¾ or ^ljC NMR spectroscopy. This was also the case when 5-bromopentan- l-ol was used as the starting material. Since the formation of 7- and 8-membered rings is not kinetically favoured, these results were not unexpected. Further, the presence of the C=0 bond on the ring is expected to distort the ring structure, further decreasing thermodynamic stability. Example 5: Various starting materials

Reactions with a number of substrates yielding 5- and 6- membered rings were screened and the results are shown in Table 2 below. The reaction mechanism is shown in Scheme 3. In Scheme 3, residues R¹, R² and R³ were methyl, phenyl or CH₂OH. While no significant difference in yield was observed when only one residue was substituted, a small decrease in yield was detected when R¹ and R³ were methyl groups. This decrease in yield may be attributed to steric hindrance as well as a change in nucleophilicity of the leaving group. In general, it was found that both 5- and 6-membered rings could be formed in moderate to excellent yield.

Scheme 3 shows the general conversion of alcohols to cyclic carbonates in the presence of Cs^COs.

Table 2. Cyclic carbonate formation with different starting

Compound X n R¹ R² R³ Yield [%]

1 CI 1 H H H 95

2 Br 0 H NA_¬ H 75

3 CI 0 C¾OH NA. H 92

A OTs 0 Ph N . H 77

5 OTs 1 H (C¾)₂ H 71

6 OTs 1 Me H Me 65

7 OTs 1 R Ph H 5

Characterization data

1 ,3-Dioxan-2-one (1) . Yield: 95%; ¹H-NMR (CDC1₃) δ = 4.45 (t, 4H, ³3HH = 5.8 Hz, O-CH ) , 2.14 (quintet, 2H, ³J_HH = 5.8 Hz, C¾) ppm; ¹³C-NMR (CDC1₃) : δ = 148.5 ( =0 ) , 68.^' 1 (0~ H₂), 21.8 ( H₂) ppm.

Ethylene carbonate (2) . Yield: 75%; ¹H-NMR (CDC1₃) : δ =4.48 is, 4H, C¾) ppm; ¹³C-NMR (CDC1₃) : 155.7 ( C=0 ) , 64.8 (C¾) ppm.

4- (Hydroxymethyl) -1 , 3-dioxolan-2-one (3) . Yield: 92%; ¹H-NMR (CDC1₃) : δ = 4.81 (m, 1H) , 4.55-4.43 (m, 2H) , 3.98 (dd, 1H, ³JH_H = 12.9 Hz, ²J_HH = 3.0 Hz) , 3.71 (dd, 1H, ³J_Hii = 12.9 Hz, J_HI] = 3.4 Hz), 2.40 (bs, 1H, OH) ppm; ¹³C-NMR (CDC1₃) : δ = 155.5 ( C=0 ) , 76.8 ( H), 65.9 (CH_:), 61.8 ( CH₂) ppm.

4-Phenyl-l ,3-dioxolan-2-one (4) . Yield: 76%; ¹H-NMR (CDC1₃) : b = 7.49-7.41 (m, 3H, Ph), 7.39-7.34 (m, 2H, Ph), 5.66 (t, 1H, ³J_m- = -8.0 Hz, CH) , 4.80 (t, 1H, ³J_HH = 8.4 Hz, C¾) , 4.35 (t, 1H, ³ _Hli = 8.4 Hz, C¾) ppm; ¹³C-N R (CDC1₃) : 0 = 154.9 ( C=0 ) , 136.0 (C_q) , 129.9 (CH, Ph) , 129.4 (CH, Ph) , 126.0 (CH, Ph), 78.1 (CH-Ph), 71.3 ( H₂) ppm.

5.5-Dimethyl-l ,3-dioxan-2-one (5) . Yield: 71%; \H-NMP. ( CDC1₃ ) : b = 4.07 (s, 4H, C¾), 1.12 (s, 6H, C¾) ppm; ¹³C-NMR ( CDC1₃ ) : 5 = 148.4 (C=0), 77.6 ( CH₂ ) , 28.6 (C(CH₃)₂), 21.3 (CH₃) ppm.

4.6-Dimethyl-l ,3-dioxan-2-one (6) . Yield: 65%; ¹H-NMR ( CDC1₃ ) : δ = 4.53 (m, 2H), 2.04 (m, 1H) , 1.54 (m, 1H), 1.34 (m, 6H) ppm. ¹³C-NMR ( CDC1₃ ) : δ = 149.6 ( C=0 ) , 75.4 (CH), 36.4 ( CH2 ) , 21.2 (CH₃) ppm. 5-Phenyl-l , 3-dioxan-2-one (7) . Yield: 95%; ^Ή-ΝΜΡ. ( CDC1₃ ) : δ = 7.42-7.31 (m, 3H, Ph), 7.23 (m, 2H, Ph), 4..61-4.49 (m, 4H, 0~ C¾) , 3.49 (m, 1H, CH) ppm; ¹³C ( CD^'C1₃ ) δ = 148.3 (C=0), 134.2 (CH-C), 129.5 (CH on bottom), 128.7 (CH in the middle), 127.6 (CH on the top next to C_q) , 72.2 (0-CH₂) , 37.7 (CH) ppm.

Applications

The disclosed method of synthesizing a cyclic carbonate may be harmless to both living organisms and the environment..

The disclosed method of synthesizing a cyclic ^'carbonate may circumvent the use of toxic and/ or poisonous starting materials The disclosed method of synthesizing a cyclic carbonate may facilitate the manufacture of cyclic carbonates in a "green" or sustainable manner.

The disclosed method of synthesizing a cyclic carbonate may provide cyclic carbonates from a plurality of alcohol starting materials . The disclosed method of synthesizing a cyclic carbonate may provide cyclic carbonates efficiently.

The disclosed method of synthesizing a cyclic carbonate may provide cyclic carbonates at a low cost of production.

The disclosed method of synthesizing a cyclic carbonate may lead to energy savings since the reaction is efficient and can be performed at ambient pressure and temperature.

The disclosed method of synthesizing a cyclic carbonate may provide cyclic carbonates that have uses in a variety of applications

The disclosed method of synthesizing a cyclic carbonate may provide cyclic carbonates that may be useful as monomers for synthesis of biocompatible polymers, polar aprotic solvents, degreasers, electrolytes and as intermediates for linear dialkyl carbonate synthesis.

The disclosed method of synthesizing a cyclic carbonate may provide cyclic carbonates that may be useful as components of batteries, adhesives, paint strippers, cosmetics and plasticizers .

It will be apparent that various other modifications and adaptations of the invention will be apparent to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the invention and it is intended that all such modifications and adaptations come within the scope of the appended claims.

Claims

1. A method of synthesizing a cyclic carbonate comprising the step of reacting an alcohol with carbon dioxide in the presence of a base.

2. The method of claim I, wherein said cyclic carbonate, has the general formula (I):

(I) wherein n is 0 or 1; and

R¹, R², R³, R⁴, R⁵ or R⁶ is independently selected from the group consisting of H, optionally substituted Ci-io-alkyl,

optionally substituted Ci-io-alkanol and. optionally substituted Cs-20-aryl.

3. The method of claim 1 or 2, wherein said alcohol has the formula ( II ) :

(ID

wherein n, R¹, R^~, R³, R⁴, R⁵ or R⁶ are the same as defined in claim ; and

X is a leaving group selected from halo, R⁷-S0₃-* , or R⁸-S0₄-

where R' is selected from the group consisting of hydrogen, optionally substituted Cx-io-alkoxy , optionally substituted Ci-io-alkyl , optionally substituted Ci-io-trihalo, and optionally substituted Cs-io-aryl;

R⁸ is selected from the group consisting of hydrogen, optionally substituted Ci-ip-alkyl, optionally substituted Ci-io-trihalo and optionally substituted C₅-i₀-aryl; and the asterisk denotes the point of attachment ^' of X to the rest of the compound.

4. The method of claim 3, wherein R¹ or R⁴ is ndependently selected from the group consisting of H, C1- 5 - Ikanol, Cs-io-aryl and Ci- 5-alkyl .

5. The method of claim 4, v/herein R¹ or R⁴ is independently selected from the group consisting of H, methanol, phenyl and methyl.

6. The method of any one of claims 3 to 5, wherein R" or

R⁵ is independently selected from the group consisting of H, C₁- 5 - alkyl and Cs-io-aryl.

7. The method of claim 5, wherein R² or R³ is independently selected from the group consisting of H, ethyl and phenyl .

8. The method of any one of claims 3 to 7, wherein R³ or R° is independently selected from the group consisting of H and Ci- 5-alkyl.

9. The method of claim 8, wherein R³ or R° is independently H or methyl.

10. The method of any one of claims 3 to 9, wherein X is selected from the group consisting of chloro, bromo, iodo,

(mesylate),

O

o=s—o-

late) , (p-toluenesulfonyl ).,

;o-toluenesulfonyl)

11. The method of claim 1 or 2, wherein said alcohol is a diol

12. The method of claim 11, further comprising the step of replacing one hydroxyl functional group of said diol with a leaving group.

13. The method of claim 12, wherein said leaving group is selected from halo, R⁷-S0₃-* or R⁸-S0₄-* , wherein R⁷ and R⁸ are as defined in claim 3.

14. The method of claim 12 or 13, wherein said replacing step comprises the step of reacting said diol with a halide selected from phosphorus trihalide or thionylhalide .

15. The method of claim 14, wherein said halide is selected from the group consisting of phosphorus trichloride, phosphorus tribromide, phosphorus triiodide, thionyl chloride and thionyl bromide.

16. The method of claim 12 or 13, wherein said replacing step comprises the step of reacting said diol with a sulfonyl halide selected from R⁹-0-S0₂-X¹ or R⁹-SO_;-X¹, wherein X¹ is selected from chloride or bromide and P.⁹ is selected from C5-20- aryl or Ci-io-alkyl .

17. The method of claim 16, wherein said reacting step further comprises an organic base selected from a N containing heteroaryl .

18. The method of any one of claims 1 to 17, wherein said base is a deprotonating agent.

19. The method of claim 18, wherein said base is an inorganic base.

20. The method of claim 18 or 19, wherein said base is a carbonate salt.

21. The method of any of claims 18 to 20, wherein said base is selected from alkali metal carbonate or alkaline earth metal carbonate.

22. The method of claim 21, wherein said base is selected from the group consisting of lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, caesium carbonate, beryllium carbonate, magnesium carbonate and calcium carbonate .

23. The method of any one of the preceding claims, wherein said base is reacted with said alcohol at a ratio in the range of about 1:1 to about 1.5:1 (base : alcohol ) ..

24. The method of any one of the preceding claims, wherein said reacting step is undertaken at a temperature in the range of about 30°C to about 50°C.

25.-. The method of any one of the preceding claims, wherein said carbon dioxide is at a pressure in the range of about 0.5 atm to about 10 atm.

26. The method of any one of the preceding claims, wherein the reacting step is undertaken for a time period in the range of about 1 to about 30 hours.

27. The method of any one of the preceding claims, comprising the step of adding a solvent to dissolve said alcohol .

28. The method of claim 27, wherein said solvent is an organic solvent.

29. The method of claim 28, wherein said organic solvent is a polar aprotic solvent.

30. The method of claim 29, wherein said polar aprotic solvent is selected from the group consisting of dimethvlformamide (DMF), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF) , ethyl acetate (EtOAc) , acetone, acetonitrile (MeCN) , hexamethylphosphoramide (HMPA) and dichloromethane .

31. The method of any one of the preceding claims, wherein said cyclic carbonate is synthesized at a yield more than 50%, more than 60%, more than 70%, more than 80%, more than 90% or more than 95% .