Lithiation of N-alkyl-(o-tolyl)aziridine: stereoselective synthesis of isochromans.

The lithiation reaction of o-tolylaziridine 1 has been investigated by using the aziridine ring capability to act as a directing metalation group. Trapped with electrophiles, the resulting o-aziridinyl benzyllithium 1-Li gives access to several functionalized aziridines 2a-j. The hydroxyalkylated derivatives 2d-j were converted into important scaffolds such as isochromans 3a-d. A stereoselective preparation of isochromans (R)-3b, (1R,3S)-3d, and (1R,3R)-3d has been developed starting from enantioenriched o-tolylaziridine.