Intramolecular 1,3-dipolar ene reactions of nitrile oxides occur by stepwise 1,1-cycloaddition/retro-ene mechanisms

The intramolecular 1,3-dipolar ene reactions of nitrile oxides are studied and it is found that the reaction consists of a three-step process consisting of a stepwise carbenoid addition of nitrile oxide for forming a bicyclic nitroso compound. Results indicate that the ring strain in the competing reaction path is responsible for achieving the ene path.