Tandem asymmetric Aza-Darzens/ring-opening reactions: dual functionality from the silane lewis acid.
The addition of a stabilized sulfur ylide (generated by the rhodium-catalyzed reaction of Ph(2)S with ethyl diazoacetate) to N-acylhydrazones promoted by a chiral silane Lewis acid leads to the highly diastereo- and enantioselective synthesis of beta-chloro-alpha-hydrazido esters. The addition of electron-rich arenes and ZnCl(2) to the reaction mixture leads to the highly diastereo- and enantioselective one-pot synthesis of diarylalanine derivatives. In both cases, the silane Lewis acid responsible for the first reaction performs the second function of activating the aziridine intermediate toward nucleophilic attack.
Department of Chemistry, Columbia University, New York, New York 10027, USA.
S Corey
SC
Valdez
James L
JL
Leighton