Diastereoselective Aza‐Mislow–Evans Rearrangement of N‐Acyl tert‐Butanesulfinamides into α‐Sulfenyloxy Carboxamides

A diastereoselective [2,3] rearrangement of O‐silyl N‐sulfinyl N,O‐ketene acetals derived from chiral N‐acyl tert‐butanesulfinamides was developed, giving α‐sulfenyloxy carboxamides with excellent enantioselectivity. Enolization and subsequent silylation of N‐acyl tert‐butanesulfinamides initiate this aza variant of the Mislow–Evans rearrangement, in which the chirality at the sulfur atom in the rearrangement precursors is faithfully transferred to the α‐carbon stereocenter of the products. The Ellman sulfinamide, often used as a chiral ammonia equivalent, can serve in this rearrangement as a chiral precursor for the asymmetric synthesis of α‐oxygen‐functionalized carboxamides. “N” for nifty: An aza variant of the Mislow–Evans rearrangement was developed that relies on the formation of rearrangement precursors reminiscent of those required for the Ireland–Claisen rearrangement. The enolization and subsequent silylation of chiral N‐acyl tert‐butanesulfinamides initiated a [2,3] sigmatropic rearrangement with faithful chirality transfer from the sulfur atom of the sulfinyl group to the α‐carbon atom of the amide (see scheme).