An Efficient Platform for Enantioselective aza -Michael Addition to Both Linear and Cyclic Enones

Abstract

We report a bifunctional phase-transfer catalytic system for the enantioselective aza-Michael addition to both linear and cyclic enones, providing β-amino carbonyls in yields up to 99% and enantioselectivities up to 98% ee. The method was evaluated across 61 examples spanning structurally diverse linear and cyclic enones, including variation in aryl and heteroaryl substitution, alkyl substitution, ring size, and cyclic acceptor class. The resulting aza-Michael adducts were further utilized as synthetic intermediates for the preparation of biologically relevant motifs, including enantioenriched divergent cyclic 1,3-amino alcohols. The synthetic utility of the method was further demonstrated through the preparation of a key intermediate en route to N14-desacetoxytubulysin H. Mechanistic studies, including control experiments, 1H NMR titration studies, and DFT calculations, are consistent with a working bifunctional dual-organization model involving cooperative catalyst–substrate interactions.