Desilylation-Activated Propargylic Transformation: Enantioselective Copper-Catalyzed [3+2] Cycloaddition of Propargylic Esters with β-Naphthol or Phenol Derivatives

Abstract

A copper-catalyzed asymmetric [3+2] cycloaddition of 3-trimethylsilylpropargylic esters with either β-naphthols or electron-rich phenols has been realized and proceeds by a desilylation-activated process. Under the catalysis of Cu(OAc)2·H2O in combination with a structurally optimized ketimine P,N,N-ligand, a wide range of optically active 1,2-dihydronaphtho[2,1-b]furans or 2,3-dihydrobenzofurans were obtained in good yields and with high enantioselectivities (up to 96 % ee). This represents the first desilylation-activated catalytic asymmetric propargylic transformation. Cu on active duty: The highly enantioselective title reaction of 3-trimethylsilylpropargylic acetates has been realized on the basis of a desilylation-activated strategy. With the support of a finely modified ketimine P,N,N-ligand, the reaction gave rise to either chiral 1,2-dihydronaphtho- or benzofurans in good yields and with up to 96 % ee.