Highly Selective and Switchable Access to Tetrasubstituted Alkenyl Sulfones and Naphthyl Sulfones: 1,4-Aryl Migration versus Cyclization.

A highly efficient, chemo-, and regioselective approach has been developed for the switchable synthesis of tetrasubstituted alkenyl sulfones and naphthyl sulfones from homopropargylic alcohols via sulfonylation/1,4-aryl migration and sulfonylation/cyclization. The present switchable processes are characterized by mild and metal-free conditions, high selectivities, good functional group tolerance, the use of inexpensive and easily handled sulfonyl hydrazides as sulfonyl sources, and the release of the nontoxic byproducts H2O and N2.