In order to construct less accessible acyclic quaternary stereocenters, a protocol was developed to α-alkynylate α,α-disubstituted N-tert-butanesulfinyl ketimines stereoselectively using 1-(2-trimethylsilylethynyl)-1,2-benziodoxol-3(1H)-one in the presence of fluoride. Despite the steric and electrical similarity between the two α-substituents, the entire reaction proceeded in a strongly stereoselective manner: tBuOK promoted α-deprotonation of the acyclic ketimine to generate stereodefined fully substituted aza-enolates, which stereoselectively formed C−C bonds with electrophilic alkynylation reagents, affording α-alkynylation products with excellent stereocontrol.

A chiral spiro phosphoric acid-catalyzed enantioselective reaction of ketenes with N–H pyrroles leads to enantioenriched C-acylated pyrroles bearing α-stereogenic carbon centres.

N-Sulfinyl metalloenamines, generated by deprotonating α-linear N-tert-butanesulfinyl ketimines, reacted with nitroalkenes via stereoselective conjugate addition to give Michael adducts with opposite stereochemistry to that obtained using α-branched sulfinylketimines. In the presence of excess base (2.5 equiv t-BuOK), the adducts derived from α-linear ketimines were further stereoselectively deprotonated to afford the corresponding kinetically favorable N-sulfinyl (Z)-enamine derivatives in good yields with good stereoselectivities. A reaction model was proposed to rationalize the observed stereochemistry.