α-Oxoketene Dithioacetals Mediated Benzoannelation of Aromatic Heterocycles: an Efficient Regiocontrolled Synthesis of Highly Substituted and Polycyclic Benzo[b]thiophenes

An efficient regiocontrolled synthesis of highly substituted and complex polycyclic benzo[b]thiophenes has been developed via our benzoannelation strategy involving conjugate addition–displacement on a variety of α-oxoketene dithioacetals by carbanions derived from 2- and 3-cyanomethylthiophenes followed by acid induced cyclization of the resulting conjugate adducts.