# US 8,541,598 B2 · Biodegradable solvents for the chemical industry

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- Number: US 8,541,598 B2
- Document ID: US8541598B2
- Status: Granted
- Kind: B2
- Application number: 12/673,200
- Filed: 2008-08-21
- Published: 2011-08-18
- Granted: 2013-09-24
- Earliest claimed: 2007-08-21
- Assignees: Dublin City University
- Applicants: Nick Gathergood; Saibh Morrissey; Bruce Pegot
- Inventors: Nick Gathergood; Saibh Morrissey; Bruce Pegot
- Web page: https://patentgrep.com/patent/US8541598B2

## CPC

- C07D 233/60: with hydrocarbon radicals, substituted by oxygen or sulfur atoms, attached to ring nitrogen atoms
- C07D: HETEROCYCLIC COMPOUNDS (macromolecular compounds C08)

## Abstract

This invention relates to ionic liquid (ILs) solvents for chemical synthesis based on an alkyl-imidazolium cation core containing ionic liquids which have enhanced biodegradability and reduced toxicity relative to existing imidazolium bases ILs such as 1-butyl-3-methylimidazolium (bmmim) salts. Many of the described ILs produce a score of over 60% biodegradability over 28 days in a biodegradability test such as the Sturm Test, the Closed Bottle Test (OECD 301D) or the CO2 Headspace Test (ISO 14593). The ILs of the invention comprise an alkyl substituted imidazolium cationic core having a —C═OX— side chain in the 3-position of the imidazole ring, wherein X═O, NH, N or S and an associated counteranion characterized in that the —C═OX side chain comprises at least one ether linkage. The biodegradable and non-toxic IL may be used as green solvents for the chemical, pharmaceutical, biofuel and biomass industries. The ILs of the invention are particularly useful in hydrogenation, pericyclic and metathesis reactions.

## Claims

### Claim 1

A compound consisting of an alkyl substituted imidazolium cationic core and an associated counter anion, wherein the imidazolium cationic core has a —C═OX— side chain in the 3-position of the imidazole ring, the —C═OX— side chain comprising a straight alkyl chain and at least one ether linkage, wherein X═O or S.

### Claim 2 (depends on 1)

The compound according to claim 1 wherein X is O and the —C═OX— side chain comprises an ester group.

### Claim 3 (depends on 1)

The compound according to claim 1 wherein the alkyl chain comprises from 4 to 13 atoms.

### Claim 4 (depends on 1)

The compound according to claim 1 wherein X is S and the —C═OX— side chain comprises a thioester group.

### Claim 5 (depends on 1)

The compound according to claim 1 characterized in that the imidazole ring is substituted with at least one C1-C4 alkyl group.

### Claim 6 (depends on 1)

The compound according to claim 1 characterized in that the imidazole ring is substituted in at least one position with at least one alkyl group selected from the group consisting of 1-methyl, 2-methyl, 4-methyl, 5-methyl, 1-ethyl, 2-ethyl, 4-ethyl, 5-ethyl, 1-propyl, 2-propyl, 4-propyl, 5-propyl and 4-trifluoromethyl.

### Claim 7 (depends on 1)

The compound according to claim 1 characterized in that the —C═OX— side chain comprises 1-4 ether linkages.

### Claim 8 (depends on 1)

The compound according to claim 1 characterized in that the —C═OX— side chain is selected from the group consisting of 2-methoxyethyl ester, 2-ethoxyethyl ester, 2-propoxyethyl ester, 2-butoxyethyl ester, 2-(2-ethoxyethoxy)ethyl ester, 2-(2-propoxyethoxy)ethyl ester and 2-(2-butoxyethoxy)ethyl ester, 2-[2-(2-methoxyethoxy)ethoxy]ethyl ester, 2-[2-(2-ethoxyethoxy)ethoxy]ethyl ester, 2-[2-(2-propoxyethoxy)ethoxy]ethyl ester and 2-[2-(2-butoxyethoxy)ethoxy]ethyl ester.

### Claim 9 (depends on 1)

The compound according to claim 1 characterized in that the —C═OX— side chain is selected from the group consisting of 2-methoxyethyl thioester, 2-ethoxyethyl thioester, 2-propoxyethyl thioester, 2-butoxyethyl thioester, 2-(2-ethoxyethoxy)ethyl thioester, 2-(2-propoxyethoxy)ethyl thioester and 2-(2-butoxyethoxy)ethyl thioester, 2-[2-(2-methoxyethoxy)ethoxy]ethyl thioester, 2-[2-(2-ethoxyethoxy)ethoxy]ethyl thioester, 2-[2-(2-propoxyethoxy)ethoxy]ethyl thioester and 2-[2-(2-butoxyethoxy)ethoxy]ethyl thioester.

### Claim 10 (depends on 1)

The compound according to claim 1 characterized in that the counter anion is selected from the group consisting of Br−, Cl−, I−, NTf2−, BF4−, PF6−, N(CN)2−, sulfate, OctOSO3−, tosylate, benzenesulfonate, hydrogen sulfate, a linear alkyl sulfate, heptadecafluorooctanesulfonate, 2-(2-methoxyethoxy)-ethylsulfate, methanesulfonate, trifluoromethanesulfonate, nonafluorobutanesulfonate, phosphate, dimethyl phosphate, diethyl phosphate, bis(pentafluoroethyl)phosphinate, bis(2,4,4-trimethylpentyl)-phosphinate, tris(pentafluoroethyl)trifluorophosphate, tris(heptafluoropropyl)trifluorophosphate, tris(nonafluorobutyl)trifluorophosphate, diethylphosphate, nitrate, thiocyanate, tricyanomethanide, bis(pentafluoroethylsulfonyl)imide, bis(trifluoromethyl)imide, tris(trifluoromethylsulfonyl)methide, bis(methanesulfonyl)amide, 2,2,2-trifluoro-N-(trifluoromethylsulfonyl)acetamide and tetracyanoborate, bis[oxalato]borate, bis-[1,2-benzenediolato(2-)]borate, bis-[salicylato(2-)]borate, bis-[malonato(2-)]-borate, bis-[2,2′biphenyl-diolato-(2-)-O,O′]-borate, acetate, trifluoroacetate, decanoate, hexafluoroantimonate, tetrachloroaluminate and cobalt tetracarbonyl.

### Claim 11 (depends on 10)

The compound according to claim 10 wherein the linear alkyl sulfate has general formula CnH2n+1OSO3−, n=1 to 8, and is selected from the group consisting of methyl sulfate, ethyl sulfate, propyl sulfate, butyl sulfate, pentyl sulfate, hexyl sulfate, heptyl sulphate, octyl sulfate and trifluoroethyl sulfate.

### Claim 12 (depends on 1)

The compound according to claim 1, characterized in that the counter anion is OctOSO3−.

### Claim 13

A compound selected from the group consisting of
KG7 (3-methyl-1-(2-[2-methoxy]ethoxycarbonylmethyl)imidazolium bromide),
KG8 (3-methyl-1-(2-[2-ethoxy]ethoxycarbonylmethyl)imidazolium bromide),
KG9 (3-methyl-1-(2-[2-propoxy]ethoxycarbonylmethyl)imidazolium bromide),
KG10 (3-methyl-1-(2-[2-butoxy]ethoxycarbonylmethyl)imidazolium bromide),
KG12 (3-methyl-1-(2-[2-methoxyethoxy]ethoxycarbonylmethyl)imidazolium bromide),
KG13 (3-methyl-1-(2-[2-ethoxyethoxy]ethoxycarbonylmethyl)imidazolium bromide),
KG14 (3-methyl-1-(2-[2-propoxyethoxy]ethoxycarbonylmethyl)imidazolium bromide),
KG15 (3-methyl-1-(2-[2-butoxyethoxy]ethoxycarbonylmethyl)imidazolium bromide),
KG16 (2,3-dimethyl-1-(2-[2-butoxy]ethoxycarbonylmethyl)imidazolium bromide),
KG18 (2,3-dimethyl-1-(2-[2-methoxyethoxy]ethoxycarbonylmethyl)imidazolium bromide),
KG23 (3-methyl-1-(2-[2-methoxy]ethoxycarbonylmethyl)imidazolium PF6),
KG24 (3-methyl-1-(2-[2-ethoxy]ethoxycarbonylmethyl)imidazolium PF6),
KG25 (3-methyl-1-(2-[2-propoxy]ethoxycarbonylmethyl)imidazolium PF6),
KG26 (3-methyl-1-(2-[2-butoxy]ethoxycarbonylmethyl)imidazolium PF6),
KG27 (3-methyl-1-(2-[2-methoxyethoxy]ethoxycarbonylmethyl)imidazolium PF6),
KG28 (3-methyl-1-(2-[2-ethoxyethoxy]ethoxycarbonylmethyl)imidazolium PF6),
KG29 (3-methyl-1-(2-[2-propoxyethoxy]ethoxycarbonylmethyl)imidazolium PF6),
KG30 (3-methyl-1-(2-[2-butoxyethoxy]ethoxycarbonylmethyl)imidazolium PF6),
KG32 (2,3-dimethyl-1-(2-[2-butoxy]ethoxycarbonylmethyl)imidazolium PF6),
KG33 (2,3-dimethyl-1-(2-[2-methoxyethoxy]ethoxycarbonylmethyl)imidazolium PF6),
KG34 (3-methyl-1-(butoxycarbonylmethyl)imidazolium octylsulfate),
KG35 (3-methyl-1-(pentoxycarbonylmethyl)imidazolium octylsulfate),
KG36 (3-methyl-1-(2-[2-methoxy]ethoxycarbonylmethyl)imidazolium octylsulfate),
KG37 (3-methyl-1-(2-[2-ethoxy]ethoxycarbonylmethyl)imidazolium octylsulfate),
KG38 (3-methyl-1-(2-[2-propoxy]ethoxycarbonylmethyl)imidazolium octylsulfate),
KG39 (3-methyl-1-(2-[2-butoxy]ethoxycarbonylmethyl)imidazolium octylsulfate),
KG40 (3-methyl-1-(2-[2-methoxyethoxy]ethoxycarbonylmethyl)imidazolium octylsulfate),
KG41 (3-methyl-1-(2-[2-ethoxyethoxy]ethoxycarbonylmethyl)imidazolium octylsulfate),
KG42 (3-methyl-1-(2-[2-propoxyethoxy]ethoxycarbonylmethyl)imidazolium octylsulfate),
KG43 (3-methyl-1-(2-[2-butoxyethoxy]ethoxycarbonylmethyl)imidazolium octylsulfate),
KG44 (2,3-dimethyl-1-(2-[2-butoxy]ethoxycarbonylmethyl)imidazolium octylsulfate),
KG45 (2,3-dimethyl-1-(2-[2-methoxyethoxy]ethoxycarbonylmethyl)imidazolium octylsulfate,
KG49 (3-methyl-1-(2-[2-methoxy]ethoxycarbonylmethyl)imidazolium NTf2),
KG50 (3-methyl-1-(2-[2-ethoxy]ethoxycarbonylmethyl)imidazolium NTf2),
KG51 (3-methyl-1-(2-[2-propoxy]ethoxycarbonylmethyl)imidazolium NTf2),
KG52 (3-methyl-1-(2-[2-butoxy]ethoxycarbonylmethyl)imidazolium NTf2),
KG53 (3-methyl-1-(2-[2-methoxyethoxy]ethoxycarbonylmethyl)imidazolium NTf2),
KG54 (3-methyl-1-(2-[2-ethoxyethoxy]ethoxycarbonylmethyl)imidazolium NTf2),
KG55 (3-methyl-1-(2-[2-propoxyethoxy]ethoxycarbonylmethyl)imidazolium NTf2),
KG56 (3-methyl-1-(2-[2-butoxyethoxy]ethoxycarbonylmethyl)imidazolium NTf2),
KG58 (2,3-dimethyl-1-(2-[2-butoxy]ethoxycarbonylmethyl)imidazolium NTf2),
KG59 (2,3-dimethyl-1-(2-[2-methoxyethoxy]ethoxycarbonylmethyl)imidazolium NTf2),
KG62 (3-methyl-1-(2-[2-methoxy]ethoxycarbonylmethyl)imidazolium BF4),
KG63 (3-methyl-1-(2-[2-ethoxy]ethoxycarbonylmethyl)imidazolium BF4),
KG64 (3-methyl-1-(2-[2-propoxy]ethoxycarbonylmethyl)imidazolium BF4),
KG65 (3-methyl-1-(2-[2-butoxy]ethoxycarbonylmethyl)imidazolium BF4),
KG66 (3-methyl-1-(2-[2-methoxyethoxy]ethoxycarbonylmethyl)imidazolium BF4),
KG67 (3-methyl-1-(2-[2-ethoxyethoxy]ethoxycarbonylmethyl)imidazolium BF4),
KG68 (3-methyl-1-(2-[2-propoxyethoxy]ethoxycarbonylmethyl)imidazolium BF4),
KG69 (3-methyl-1-(2-[2-butoxyethoxy]ethoxycarbonylmethyl)imidazolium BF4),
KG71 (2,3-dimethyl-1-(2-[2-butoxy]ethoxycarbonylmethyl)imidazolium BF4),
KG72 (2,3-dimethyl-1-(2-[2-methoxyethoxy]ethoxycarbonylmethyl)imidazolium BF4),
KG75 (3-methyl-1-(2-[2-methoxy]ethoxycarbonylmethyl)imidazolium N(CN)2),
KG76 (3-methyl-1-(2-[2-ethoxy]ethoxycarbonylmethyl)imidazolium N(CN)2),
KG77 (3-methyl-1-(2-[2-propoxy]ethoxycarbonylmethyl)imidazolium N(CN)2),
KG78 (3-methyl-1-(2-[2-butoxy]ethoxycarbonylmethyl)imidazolium N(CN)2),
KG79 (3-methyl-1-(2-[2-methoxyethoxy]ethoxycarbonylmethyl)imidazolium N(CN)2),
KG80 (3-methyl-1-(2-[2-ethoxyethoxy]ethoxycarbonylmethyl)imidazolium N(CN)2),
KG81 (3-methyl-1-(2-[2-propoxyethoxy]ethoxycarbonylmethyl)imidazolium N(CN)2),
KG82 (3-methyl-1-(2-[2-butoxyethoxy]ethoxycarbonylmethyl)imidazolium N(CN)2),
KG84 (2,3-dimethyl-1-(2-[2-butoxy]ethoxycarbonylmethyl)imidazolium N(CN)2),
KG85 (2,3-dimethyl-1-(2-[2-methoxyethoxy]ethoxycarbonylmethyl)imidazolium N(CN)2),
KG405 (3-methyl-1-[bis-1-methoxyethyl]carbamylmethyl)imidazolium octylsulfate) and
KG407 (3-methyl-1-[bis-1-methoxyethyl]carbamylmethyl)imidazolium bromide)
KG422 (3-methyl-1-[1-methoxyethyl]carbamylmethyl)imidazolium bromide),
KG423 (3-methyl-1-[1-methoxypropyl]carbamylmethyl)imidazolium bromide).

### Claim 14 (depends on 1, 13)

A method of preparing the compound according to claim 1 or 13 comprising the steps of:
forming a halo ester alkylating agent by reacting an alcohol comprising an ether or polyether group with halo acetyl halide; and
reacting said halo ester alkylating agent with an imidazole to form an imidazole ester halide salt.

### Claim 15 (depends on 14)

The method as claimed in claim 14 wherein the halo acetyl halide is selected from the group consisting of bromo acetyl bromide, chloro acetyl chloride, bromo acetyl chloride and chloro acetyl bromide.

### Claim 16 (depends on 14)

The method according to claim 14 wherein the halide salt is reacted with an alkali salt in an anion exchange reaction, the alkali salt comprising an NTf2−, BF4, PF6−, N(CN)2−, or an OctOSO3− anion.

### Claim 17 (depends on 14)

The method according to claim 14 wherein the compound comprises an ether linkage containing chain which is selected from the group consisting of 2-methoxyethyl ester, 2-ethoxyethyl ester, 2-propoxyethyl ester, 2-butoxyethyl ester, 2-(2-ethoxyethoxy)ethyl ester, 2-(2-propoxyethoxy)ethyl ester and 2-(2-butoxyethoxy)ethyl ester, 2-[2-(2-methoxyethoxy)ethoxy]ethyl ester, 2-[2-(2-ethoxyethoxy)ethoxy]ethyl ester, 2-[2-(2-propoxyethoxy)ethoxy]ethyl ester, 2-[2-(2-butoxyethoxy)ethoxy]ethyl ester.

### Claim 18

A method of improving the biodegradability or reducing the toxicity of an imidazole cation containing ionic liquid wherein the imidazole cation comprises an ester or thioester side chain at the 3-position of the imidazole ring, the side chain comprising a straight chain alkyl group, the method comprising the step of introducing at least one ether group into the side chain.

### Claim 19 (depends on 18)

The method as claimed in claim 18 further comprising the step of introducing an OctOSO3− anion into the ionic liquid.

### Claim 20 (depends on 1, 13)

A method of reducing toxicity and/or increasing biodegradability of a chemical reaction, a biomass dissolution or a biofuel preparation, the method comprising the step of using the compound as claimed in claim 1 or 13 as a solvent or co-solvent, wherein the chemical reaction is selected from the group consisting of enzymatic and biocatalytic reactions, neutralizations, acidifications, basifications, oxidations, reductions, hydrogenation reactions, radical reactions, electrophilic additions, electrophilic substitutions, nucleophilic additions, nucleophilic substitutions, rearrangements, pericyclic reactions, and metathesis reactions.

### Claim 21 (depends on 20)

The method according to claim 20 wherein the biomass dissolution is a cellulose dilution.

### Claim 22 (depends on 20)

The method according to claim 20 wherein the chemical reaction is a hydrogenation reaction.

### Claim 23 (depends on 20)

The method according to claim 20 wherein the chemical reaction is a metathesis reaction.

### Claim 24 (depends on 20)

The method according to claim 20 wherein the chemical reaction is a pericyclic reaction.

### Claim 25 (depends on 22)

The method according to claim 22 wherein the hydrogenation reaction is selective reduction of trans-cinnamaldehyde to hydrocinnamaldehyde in the presence of hydrogen gas and palladium supported on carbon.

### Claim 26 (depends on 22)

The method according to claim 22 wherein the hydrogenation reaction is selective reduction of the alkene bond conjugated to the carbonyl group of benzyl cinnamate using hydrogen gas and palladium supported on carbon.

### Claim 27 (depends on 20)

The method according to claim 20 wherein the compound is 3-methyl-1-(2-[2-propoxy]ethoxycarbonylmethyl)imidazolium NTf2.

### Claim 28 (depends on 1, 13)

A method of preparing the compound of claim 1 or 13 comprising the steps of:
forming a halo thioester alkylating agent by reacting a thiol comprising an ether or polyether group with halo acetyl halide; and
reacting said halo thioester alkylating agent with an imidazole to form an imidazole thioester halide salt.

### Claim 29 (depends on 28)

The method of claim 28, wherein the halo acetyl halide is selected from the group consisting of bromo acetyl bromide, chloro acetyl chloride, bromo acetyl chloride and chloro acetyl bromide.

### Claim 30 (depends on 28)

The method of claim 28, wherein the halide salt is reacted with an alkali salt in an anion exchange reaction, the alkali salt comprising an NTf2−, BF4, PF6−, N(CN)2−, or an OctOSO3− anion.

### Claim 31 (depends on 28)

The method of claim 28, wherein the compound comprises an ether linkage containing chain which is selected from the group consisting of 2-methoxyethyl thioester, 2-ethoxyethyl thioester, 2-propoxyethyl thioester, 2-butoxyethyl thioester, 2-(2-ethoxyethoxy)ethyl thioester, 2-(2-propoxyethoxy)ethyl thioester, 2-(2-butoxyethoxy)ethyl thioester, 2-[2-(2-methoxyethoxy)ethoxy]ethyl thioester, 2-[2-(2-ethoxyethoxy)ethoxy]ethyl thioester, 2-[2-(2-propoxyethoxy)ethoxy]ethyl thioester and 2-[2-(2-butoxyethoxy)ethoxy]ethyl thioester.