Lewis Acid-Catalyzed Addition of Benzophenone Imine to Epoxides Enables the Selective Synthesis and Derivatization of Primary 1,2-Amino Alcohols

Abstract

Benzophenone imine was found to be an effective ammonia surrogate for the selective preparation of primary 1,2-amino alcohols from epoxides, including enantiopure epichlorohydrin, in the presence of catalytic Y(OTf)3. High-throughput screening of 48 Lewis acids quickly identified Y(OTf)3 as an effective mediator of the addition reaction under mild conditions. Following acidic hydrolysis, the primary amino alcohol salt is revealed and partitions into the aqueous solution, while the benzophenone byproduct is easily removed by simple extraction with ethyl acetate. These ammonium salts can be directly Boc-protected or further derivatized without isolation to form benzamides and sulfonamides under Schotten–Baumann-type conditions in up to 79% isolated yield over three steps. This methodology has been used to prepare key intermediates for the synthesis of PRMT5 inhibitors with high enantiopurity as well as numerous other amide and sulfonamide derivatives.