Synthesis of benzo[b]thiepins, a class of 12π-electron heterocycles

Abstract

3,4-Dimethoxycarbonyl-5-pyrrolidin-1-ylbenzo[b]thiepin has been prepared in a one-step synthesis by cycloaddition of 3-pyrrolidin-1-ylbenzo[b]thiophen (Ia) to dimethyl acetylenedicarboxylate; upon being heated, benzo[b]thiepins of this type rearrange to give naphthalenes and upon oxidation they yield thermally stable 1,1-dioxides.