Stereocontrolled α-Allylation of α-Branched N-tert-Butanesulfinyl Ketimines via a Michael-Wittig Cascade for the Construction of Acyclic Quaternary Stereocenters

Stereoselective Construction of Acyclic β,β-Disubstituted Enesulfinamides via Conjugate Addition of Organocuprates to α-Substituted α,β-Unsaturated N-Sulfinyl Ketimines

In the presence of boron trifluoride, conjugate addition of organocuprates to α-substituted α,β-unsaturated N-tert-butanesulfinyl ketimines provides facile access to acyclic β,β-disubstituted enesulfinamides with high ratios of geometric isomers. Diverse and challenging to synthesize, multisubstituted aza-enolates bearing two electronically and sterically similar β-substituents, which are important precursors for asymmetric construction of the less accessible acyclic quaternary or tetrasubstituted stereocenters at the α-position of ketimines, can be efficiently prepared in good yields with high stereocontrol.

Stereoselective Synthesis of Less Accessible α-Tertiary Amino Ketimines via Electrophilic Amination of α-Branched N-tert-Butanesulfinyl Ketimines

A stereocontrolled electrophilic amination of α-branched N-tert-butanesulfinyl ketimines was developed to construct α-aminoketone derivatives containing less accessible α-tetrasubstituted stereocenters. Stereospecific α-deprotonation of ketimines with potassium tert-butoxide gave stereodefined metalloenamine intermediates that could act as nucleophiles to attack azodicarboxylic derivatives, affording α-aminated products in high yields with excellent stereoselectivities.