Novel ringtransformations of pyrimidines and pyridines by intramolecular inverse electron demand Diels-Alder reactions

2-(1,1-Dicyanopent-4-yn-1-yl)pyrimidines (1) and 2-(1,1-dicyanopent-4-yn-1-yl)nitropyridines (4) undergo intramolecular inverse electron demand Diels-Alder cycloaddition across the C2-C5 positions; these adducts lose hydrogen cyanide instantaneously, yielding 7,7-dicyano-6,7-dihydro-5H-1-pyrindines (3) and 1,1-dicyano-2,3-dihydronitroindenes (6), respectively. The intramolecular cyclo-additions of the pyridine derivatives represent the first examples of inverse electron demand reactions in pyridines.