Development of molecular mechanics torsion parameters for alpha,beta-cyclopropyl alpha',beta'-enones and conformational analysis of bicyclo[m.1.0]alk-3-en-2-ones

Conformations of cyclopropyl vinyl ketone have been studied using ab initio methods in an effort to quantify the effects of conjugative overlap between the cyclopropane ring and adjacent enone carbonyl. With respect to the cyclopropyl carbonyl torsion, cyclopropyl vinyl ketone exhibits a global energy minimum in the s-cis conformer and a local energy minimum in the s-trans conformer. The potential energy curve obtained was used to derive torsion parameters which were employed in molecular mechanics studies of the conformations of the set of bicyclo[m.1.0]alk-3-en-2-ones having larger ring sizes from 5- to 16-membered.