Novel N-(2-benzo[b]thienyl)iminophosphoranes and their use in the synthesis of benzo[b]thieno[2,3-b]pyridines

Novel N-(2-benzo[b]thienyl)iminophosphoranes react with α,β-unsaturated aldehydes and ketones to give benzo[b]thieno[2,3-b]pyridines in an aza-Wittig/electrocyclic-ring closure process. The diphenylmethyliminophosphorane reacts with aromatic and heteroaromatic aldehydes to give iminic products: upon UV irradiation, two imines furnish cyclization products in acceptable yields.