SYMMETRIC THIOINDIGO COMPOUND AND MANUFACTURE OF SYMMETRIC AND ASYMMETRIC THIOINDIGO COMPOUND

摘要

Symmetrical thioindigo compounds (I) IMAGE where R is as defined in claim 1, or mixtures of compounds (I) with asymmetrical thioindigo compounds in which at least one R in a 4- to 7-position is nonidentical to a substituent R in a 4'- to 7'-position and R otherwise is as defined in claim 1, can be obtained by a novel process in a simple, economical manner and high purity by first reacting certain 2,3-dihalo-maleic or -fumaric acid derivatives, in particular 2,3-dichloromaleic anhydride, with a substituted or unsubstituted thiophenol or a mixture of two different thiophenols. The resulting bis-2,3-(thiophenyl)-maleic or -fumaric acid derivatives are subsequently cyclised to give the corresponding 2-thiophenylcarboxymethylene[2H]benzothiophen-3-ones or derivatives thereof, whereupon these compounds are subjected to a further cyclisation. The thioindigo compounds which are preparable according to the invention are known in part and are used in particular as vat or pigment dyes or for transfer printing.