Metal-free synthesis of biaryls from aryl sulfoxides and sulfonanilides via sigmatropic rearrangement

Abstract

Treatment of aryl sulfoxides and sulfonanilides with trifluoroacetic anhydride resulted in the dehydrative metal-free construction of the corresponding unsymmetrical biaryls. The reaction would proceed via (1) the activation of aryl sulfoxide with the anhydride, (2) interrupted Pummerer reaction of the resulting arylsulfonium with sulfonanilide, (3) [3,3] sigmatropic rearrangement to cleave the transient S–N bond and to form the prospective biaryl C–C bond, and (4) global aromatization. The choice of the amino protecting group is crucial, and only N-sulfonylanilines, i.e., sulfonanilides, could participate in the formation of biaryls.