PROCESS FOR PREPARING BENZO1,2-B;4,5-B'DITHIOPHENE-4,8-DICARBOXYLIC ACID OR ITS 2,3-DIHYDRO DERIVATIVE

摘要

The invention relates to a process for preparing benzo[1,2-b;4,5- b']dithiophene-4,8-dicarboxylic acid or its 2,3-dihydro derivative, and to novel products prepared by this process which comprises the following steps: A) heating benzo[1,2-b;4,5-b']dithiophene-4,4,8,8-tetracarboxylic acid, or an acid derivative thereof, in an organic solvent in the presence of a base and an oxidising agent, and adding an acid, to give benzo[1,2-b;4,5-b']dithiophene-4,8-dicarboxylic acid, or B) heating benzo[1,2-b;4,5-b']dithiophene-4,4,8,8-tetracarboxylic acid, or an acid derivative thereof, in a polar organic solvent in the presence of a base under exclusion of an oxidising agent, and adding an acid, to give 2,3-dihydrobenzo[1,2-b;4,5-b']dithiophene-4,8- dicarboxylic acid.