Cycloadditions of Nitrile Oxides to α,β-Unsaturated Aldehydes. Frontier Orbital Interactions and Secondary Orbital Interactions at Work in Determining Regiochemistry

The regiochemistry of the cycloadditions of nitrile oxides to crotonaldehyde and cinnamaldehyde has been determined and is dictated by frontier orbital interactions and secondary orbital interactions as well. In cycloadditions to α,β-unsaturated compounds the directive effect of the frontier orbital interactions can be diverted by steric drifts and secondary orbital interactions.