Applicable β-sulfonium carbanions: facile construction of thiophene derivatives

beta-Sulfonium carbanions, members of the organosulfur family, are ephemeral intermediates and difficult to apply in organic syntheses. We developed a new strategy toward relatively stable beta-sulfonium carbanions, achieved by an intramolecular addition of the sulfur atom of a sulfide to the in situ generated electron-deficient allene moiety. These types of applicable beta-sulfonium carbanions may indicate an unexplored area in which a bundle of synthetically useful building blocks are yet to be discovered.