Competing Diels–Alder reactions of activated nitroethylene derivatives and [3,3]-sigmatropic rearrangements of the cycloadducts

Diels–Alder reaction of nitroethylene derivatives with cyclohexa-1,3-diene afforded three pericyclic products some of which could be converted to others via a new [3,3]-sigmatropic rearrangement or via a Claisen rearrangement.