METHOD OF PURIFYING DIALKYL ESTERS OF (6-CHLORO-2-CARBAZOYL)METHYLMALONIC ACID S

• Main Authors: ROSE PETER ROBERT, DEVRIES KEITH MICHAEL, RESCEK DIANE MARIE, TUCKER JOHN LLOYD, HAMMEN PHILIP DIETRICH
• Format: Patent
• Language: English
• Published: 20.12.1999
• Edition: 6
• Subjects: CHEMISTRY; HETEROCYCLIC COMPOUNDS; METALLURGY; ORGANIC CHEMISTRY

A process of purifying a (6-chloro-2-carbazolyl)methyl-malonic acid di(C1 -C6 alkyl) ester of 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 DEG to about 110 DEG 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 DEG to about 70 DEG C, and said phase separation is carried out only once.