One-Pot Synthesis of Substituted 2-Aminobenzo[b]thiophenes

Significance

This paper describes a convenient one-pot synthesis of 2-aminobenzo[b]thiophenes which involves the Willgerodt-Kindler reaction as the first step. Thus, as expected from the Will­gerodt-Kindler process, reaction of the aceto­phenone derivative with sulfur and primary or secondary amines leads to a thioamide. However, the presence of the nitro group para to the chloro substituent promotes a nucleophilic aromatic substitution reaction to afford the benzothiophene product. Primary amines gave the best results while bulky amines gave low yields of products. An isothiazole derivative was obtained (78% yield) in an attempt to prepare an unsubstituted benzo­thiophene.