Patent ID: 6649758
Filing Date: 2003-11-18
Classification: C09B

Abstract:
A process for preparing symmetrical or asymmetrical trans-thiazineindigo pigments of the formula (1) whereR1 and R2 are identical or different and each is a radical required to complete a ring system selected from the group consisting of aromatic carbocyclic ring systems, aromatic heterocyclic ring systems, aliphatic carbocyclic ring systems and aliphatic heterocyclic ring systems, said ring systems optionally being substituted, and R3 is hydrogen, C1-C12-alkyl or phenyl, which comprisesa) condensing, in an aqueous medium, a compound of the formula (2) with a compound of the formula (3a) or (3b); or a compound of the formula (4) with a compound of the formula (3a), or (3b), or (3a) and (3b) whereR4 is hydrogen or a metal ion selected from the group consisting of Na+, K+and Zn2+/2, R5 is a leaving group, and Hal is Cl or Br; by maintaining the reaction mixture at a temperature between 30 and 65Â° C. for at least 1 hour and then b) maintaining the reaction mixture at a temperature between 100 and 180Â° C. and a pressure between 1.5 and 50 bar for at least 1 hour in the presence of an amide.