Recovery and recycling of chiral tartaric acid resolving agents
A process for the recovery of substituted tartaric acid resolving agents from resolution process liquors comprising organic solvents, wherein the substituted tartaric acid derivatives are neutralised by adding a base, extracted into an aqueous phase and crystallized from the aqueous phase by addition of a mineral acid in the presence of an organic solvent.
1. A process for recovering a substituted tartaric acid resolving agent from a resolution process liquor,
wherein the resolution process liquor comprises an organic solvent, and a substituted tartaric acid resolving agent of the formula:
said process comprising:
A) adding a base to the resolution process liquor to neutralize the substituted tartaric acid resolving agent;
B) extracting the liquor obtained in A) into an aqueous phase; and
C) adding a mineral acid and a water soluble or partly water soluble organic co-solvent to the aqueous phase obtained in B) to crystallize a substituted tartaric acid resolving agent from the aqueous phase.
2. A process according to claim 1 wherein the substituted tartaric acid resolving agent is chosen from (+)-di-O,O′-toluoyl-(D)-tartaric acid, (−)-di-O,O′-toluoyl-(L)-tartaric acid, (+)-di-O,O′-benzoyl-(D)-tartaric acid, or (−)-di-O,O′-benzoyl-(L)-tartaric acid.
3. A process according to claim 1 wherein the base is added as an aqueous solution.
4. A process according to claim 1 wherein the substituted tartaric acid resolving agent is neutralized by a hydroxide, carbonate or hydrogen carbonate salt of an alkali or alkaline earth metal or ammonia.
5. A process according to claim 1 wherein the organic co-solvent is a C 1 to 10 -alcohol.
6. A process according to claim 1 wherein the organic co-solvent is 2-butanol.
7. A process according to claim 1 wherein the mineral acid is hydrochloric acid, hydrobromic acid, or sulfuric acid.
8. A process according to claim 1 wherein the mineral acid is hydrochloric acid.
9. A process according to claim 1 wherein the substituted tartaric acid resolving agent is crystallised in the form of a solvate with the co-solvent.