A MINDO/3 and NDDO study of antiaromatic three-membered rings and their valence tautomers

Abstract

Calculations using MINDO/3 and a newly parameterised version of NDDO indicate that antiaromatic heterocyclic analogues of the cyclopropenyl anion should be stable and may therefore occur as stable intermediates in reactions; calculations are also reported for the isomeric cyclic carbenes (hetero-analogues of cyclopropylidene) and for the isomeric acyclic carbenes (e.g. HCO–CH:), the acyclic carbenes being predicted to rearrange to the corresponding antiaromatic heterocycles without activation.