Patent ID: 6984739

Claim:
A process for the preparation of S-(−)-chlorosuccinic anhydride comprising a) reacting S-(+)-aspartic acid and sodium nitrite in a hydrochloric acid-aqueous milieu in which said S-(+)-aspartic acid suspended in demineralized water in a w/w ratio ranging from 1 kg/L to 0.5 kg/L, and concentrated hydrochloric acid is added in a ratio of S-(+)-aspartic acid to hydrochloric acid ranging from 0.35 kg/L to 0.55 kg/L in the presence of sodium chloride, said S-(+)-aspartic acid and said sodium chloride being in a molar ratio ranging from 1:0.3 to 1:0.5, to give crude S-(−)-chlorosuccinic acid; b) isolating said crude S-(−)-chlorosuccinic acid by precipitation by cooling the reaction mixture at a temperature ranging from−10° C. to−20° C.; and c) reacting said isolated crude S-(−)-chlorosuccinic acid and acetic anhydride.