METHOD OF PURIFYING CARBAZOLE ESTER PRECURSORS OF 6-CHLORO-.ALPHA.-METHYL-CARBAZOLE-2-ACETIC ACID

摘要

A process of purifying a (6-chloro-2-carbazolyl)methyl-malonic acid di(C, -Cs alkyl) ester of Formula (I): (see formula I) wherein Ra and Rb must be the same and are selected from the group consisting of C1-C6 alkyl; comprises phase separating one or more impurities from said carbazole ester at least once wherein the solvent used to carry out said phase separation is acetic acid. In a preferred embodiment said acetic acid is glacial acetic acid which is maintained at a temperature of from about 30.degree. to about 110.degree. C and said carbazole ester is obtained in a purity of at least 99. 90% by weight, so that the amount of impurities present therein is 0.10% or less by weight. In a more preferred embodiment of said process, said temperature is from about 50.degree. to about 70.degree. C, and said phase separation is carried out only once.