Stereodivergent Construction of Cyclic Ethers by a Regioselective and Enantiospecific Rhodium-Catalyzed Allylic Etherification:Total Synthesis of Gaur Acid

摘要

The transition-metal-catalyzed intermolecular allylic ether-ification is a fundamentally important cross-coupling strategy for the construction of enantiomerically enriched allylic ethers.Although there are numerous examples of the use of simple primary alcohols as nucleophiles,secondary or tertiary alcohols have been used in relatively few studies,partially because of the poor nucleophilicity of these alcohols and the high basicity of the corresponding alkali-metal alkoxides.In response to these underlying problems,we recently reported a regioselective and enantiospecific rhodium-catalyzed allylic etherification with copper(I) alkoxides as nucleophiles.The transmetalation of an alkali-metal alkoxide served to diminish its basicity,thereby promoting the etherification of a soft metal-allyl electrophile.