Dual orbital effects in N-philic cyclizations of silyl radicals onto imines

Abstract

Density functional studies revealed that nucleophilic silyl radicals are able to mask as electrophiles by cyclizing with high preference onto the more electron-rich nitrogen atom of imine C=N double bonds. This remarkable behavior is a result of a combination of SOMO-π* and lone pair (LP)-σ* interactions during the reaction. If the LP is not available due to steric reasons, attack of the Si-radical occurs with slight preference at the carbon atom. This indicates that "dual orbital" interactions are directing the regioselectivity of silyl radical cyclizations. Copyright © 2007 The Chemical Society of Japan.