Chiral Base-Catalyzed Enantioselective Synthesis of 4-Aryloxyazetidinones and 3,4-Benzo-5-oxacephams

Abstract

Readily available 4-formyloxyazetidinone was enantioselectively transformed into 3,4-benzo-2-hydroxy-5-oxacephams and 4-phenyloxyazetidinones upon treatment with 0.1 equiv of the cinchona alkaloid in toluene via intermolecular nucleophilic trapping of N-acyliminium intermediate by the hydroxyl moiety of phenols or o-hydroxybenzaldehydes. Additionally, the absolute configuration of title compounds was established by CD spectroscopy.