DEVELOPMENT OF MOLECULAR MECHANICS TORSION PARAMETERS FOR ALPHA,BETA-CYCLOPROPYL KETONES AND CONFORMATIONAL-ANALYSIS OF BICYCLO[M.1.0]ALKAN-2-ONES

Conformations of cyclopropyl methyl ketone have been studied using ab initio methods in an effort to quantify the effects of conjugative ove rlap between the cyclopropane ring and an adjacent ketone carbonyl. Re sults were comparable with previous experimental and theoretical studi es. Cyclopropyl methyl ketone exhibits a global energy minimum in the s-cis conformer and a local energy minimum near the s-trans conformer. The potential energy curve obtained was used to derive torsion parame ters which were employed in molecular mechanics studies of the conform ations of the set of bicyclo[m.1.0]alkan-2-ones having larger ring siz es from five- to 16-membered. Similar conformations for the cyclopropy l ketone substructure are observed for all the medium and large ring s ystems examined. Possible synthetic ramifications of local conformatio nal anchoring by this functional group array are discussed.