The Brønsted Acid-Catalyzed Direct Aza-Darzens Synthesis of <i>N</i>-Alkyl <i>cis</i>-Aziridines

Abstract

A mild protocol for the synthesis of cis-aziridines is described that employs a catalytic amount of Brønsted acid. Despite the potential for diazo compound decomposition via alkylation or homocoupling upon exposure to a proton source, these pathways are slow relative to [2 + 1] annulation in the presence of a Schiff base, leading to aziridine product. The process uses no metals or reagents that must be removed chromatographically, exhibits rapid turnover rates, and produces only atomic nitrogen as a coproduct. High levels of relative stereocontrol are also possible when forming the Schiff base from a chiral nonracemic aldehyde.