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.