Stereocontrolled Construction of Acyclic Quaternary Carbon Centers via α-Hydroxymethylation of α-Branched <i>N</i>-<i>tert</i>-Butanesulfinyl Ketimines.

Hydroxymethylation of α-branched <i>N</i>-<i>tert</i>-butanesulfinyl ketimines with formaldehyde equivalents was developed to stereoselectively construct acyclic quaternary stereocenters bearing two sterically and electronically similar substituents. The stereoselective <i>t</i>BuOK-promoted α-deprotonation of acyclic ketimines allowed for the stereodefined formation of fully substituted aza-enolates, followed by facially selective C-C bond formation involving formaldehyde formed <i>in situ</i>, yielding α-hydroxymethylated products with precise stereocontrol.