Synthesis of Functionalized Azetidines through Chemoselective Zinc-Catalyzed Reduction of β-Lactams with Silanes

摘要

An efficient method for the one-step conversion of β-lactams to their corresponding functionalized azetidines has been developed. This approach takes advantage of the selective reduction of the 2-azetidinone nucleus with hydrosilanes in the presence of a zinc-based catalyst. The methodology is tolerant towards sensitive groups such as allene, ester, and cyanohydrin moieties. In addition, the process allows the preparation of enantiopure azetidines without erosion of the stereochemical integrity. A catalytic cycle involving an azetidinium salt intermediate has been proposed.