Benzofuran Synthesis from N -Aryloxysulfonamides and 2-Bromoallyl Sulfones via Sequential Treatment with Base and Acid

Abstract Sequential treatment of N-aryloxysulfonamides and 2-bromoallyl sulfones with cesium carbonate and p-toluenesulfonic acid led to the formation of 2-(arylsulfonylmethyl)benzofurans. An initial formal nucleophilic vinylic substitution sets the stage for a room-temperature [3,3]-sigmatropic rearrangement of the O-aryl-N-vinyl hydroxylamine intermediate. An allenoate ester also reacted analogously to afford the corresponding benzofuran-esters.