Highly enantioselective Rh-catalyzed intramolecular Alder-ene reactions for the syntheses of chiral tetrahydrofurans

Abstract

Over 99% ee was obtained for all the tested substrates in a Rh-catalyzed Alder-ene reaction. Simply mixing air-stable, commercially available [{Rh(cod)Cl}2] (cod = 1,5-cyclooctadiene) and 2,2′-bis(diphenylphosphanyl)-1,1′-binaphthyl (binap) at room temperature afforded functionalized and chiral tetrahydrofurans in high yields with high efficiency (turnover frequency: 1500 h-1). The catalyst loading was as low as 0.8 mol %.