Département de chimie moléculaire

Exptl. and computational investigations of anti-Bredt amidinium salts are presented. Calcns. show that the pyramidalization of an amino group can significantly destabilize the formal carbocation center of amidiniums, due to the decreased $π$ donation. In some cases, the unfavorable -I effect of nitrogen surpasses its beneficial +M effect, and amidiniums become less stable than iminiums. It is shown that although 1-aza-3-azonia[3.3.1]bicyclo-non-2-enes can be isolated, they feature a nonclassical reactivity, which is more typical for iminium than amidinium salts, such as pronounced electrophilicity and azomethine ylide instead of carbene formation. [on SciFinder(R)]