Conrotatory Ring-Opening Reactions of Cyclopropyl Anions in Monocyclic and Tricyclic Systems

Only conrotatory transition structures were located by B3LYP6-311++G(3df, 2p) computations for the electrocyclic ring opening of cyclopropyl anions having different substituents (H, Me, CN). The transition structure for the similarly substituted cyclopropyl anion fused to a bicyclic system exhibits the same features, in apparent contradiction with the observed product. A reaction path where the direction of twist changes after the transition state provides an explanation alternative to those proposed in recent reports.