Combined intra-intermolecular criss-cross cycloaddition reactions leading to perfluoroalkylated fused tricyclic nitrogen heterocycles

Perfluoroalkylated hydrazones 1a–e were prepared from diethyl hydrazinophosphate and were engaged in the reaction with 3-substituted homoallenyl aldehydes according to Zwierzakʹs method. The resulting non-symmetrical perfluoroalkyl-derived azines reacted in combined intra-intermolecular criss-cross cycloaddition with phenyl isocyanate, phenyl isothiocyanate and dimethyl acetylenedicarboxylate producing fused tricyclic heterocycles. Besides, the thermal cyclization of perfluoroalkylated non-symmetrical azines, without added dipolarophile, was carried out providing fused bicyclic systems.