Acid catalyzed alpha-alkylation of beta-aminothiophenes with aldehydes. Synthesis of 2-alkyl 3-thiophenamines, bis(3-amino-2-thienyl)methane derivatives and dithieno[3,2-b:2',3'-e]pyridines

The acid catalyzed reaction of 3-thiophenamines with aldehydes in the presence of selenophenol as the reducing agent, gives 2-alkyl-3-thiophenamines. Without reduction, bis(3-amino-2-thienyl)methane derivatives have been obtained and transformed into dithieno[3,2-b:2',3'-e]pyridines by thermal and acidic treatment when the substrates are primary amines. These new tricyclic heterocycles can be synthesized in a one-pot procedure from 3-thiophenamine.