Stereodivergent Construction of Vicinal Acyclic Quaternary-Tertiary Carbon Stereocenters by Michael-Type Alkylation of α,α-Disubstituted N-tert-Butanesulfinyl Ketimines.

Vicinal quaternary-tertiary carbon stereocenters were constructed with excellent stereoselectivity via aza-enolization of enantioenriched acyclic N-tert-butanesulfinyl ketimines bearing two sterically similar α-linear alkyl substituents followed by conjugate addition to nitroalkenes. Further changes of the absolute configuration of the sulfinyl group and/or the α-stereocenter in the ketimine allowed the facile stereodivergent synthesis of all four diastereomers of the Michael-type alkylation adducts. This reaction is a successful example of acyclic stereocontrol based on stereoselective α-deprotonation for the formation of fully substituted aza-enolates from ketone derivatives.