Stereochemistry of the Kulinkovich cyclopropanation of nitriles.

The stereochemistry of the Kulinkovich cyclopropanation of nitriles with alkenes has been examined by employing (E)-disubstituted alkenes and deuterium-labeled homoallylic alcohols as a stereochemical probe. An intramolecular cyclopropanation proceeds with preservation of the olefin configuration. On the other hand, intermolecular counterparts occur with both preservation and reversal of the olefin configuration, which corresponds to retention and inversion of configuration at the Ti-C bond, respectively, in the cyclopropane-forming step. These uncommon stereochemical outcomes contrast with that of the Kulinkovich cyclopropanation of tertiary amides.