Abstract Vilsmeier's reagent treatment of substituted diphenacyl sulfides or diphenacyl disulfides has led to the formation of a series of benzfused 3-chlorothiophene-2- carbaldehydes by a Domino Vilsmeier–Haack reaction/ring closure sequence, opening a new route for the synthesis of 3-chlorobenzo [b] thiophene-2-carbaldehydes and their benzfused analogues. A plausible mechanism has been proposed.
