Phosphite-Gold(I)-Catalyzed [2+2]Intermolecular Cycloaddition of Enol Ethers with N-Allenylsulfonamides

Addition of catalytic amounts of a phosphite-based gold(I) catalyst efficiently triggers the intermolecular [2+2]?cycloaddition of allenes and alkenes substituted by electron-donor groups. The reaction is fast and furnishes cyclobutane derivatives in a stereoselective manner using low catalyst loadings. Besides, the same catalyst selectively affords homodimerization products from the starting allene, a process that may be conveniently fine tuned by addition of norbornene.