Synthesis of thieno[2,3-b]pyrrole-2(4)-carboxylic and 2,4-dicarboxylic acids

Abstract

1-Substituted 5-chloro-4-formylpyrrole-3-carboxylates reacted with thioglycolic acid or ethyl thioglycolate in EtOH containing EtONa at room temperature, forming 4-(ethoxycarbonyl)thieno[2,3-b]pyrrole-2-carboxylic acids or thieno[2,3-b]pyrrole-2,4-dicarboxylates. Cyclocondensation with thioglycolic acid upon refluxing in K2CO3–DMF system was accompanied by decarboxylation and led to the formation of thieno[2,3-b]pyrrole-4-carboxylates. Hydrolysis of the obtained carboxylates with LiOH provided thieno[2,3-b]pyrrole-2(4)-carboxylic and 2,4-dicarboxylic acids.