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

• Fused three five-membered nitrogen heterocycles were prepared.
• Combined intra-intermolecular criss-cross cycloaddition reactions were presented.
• Synthesis of new fluorinated dihydropyrrolo[1,2-b]pyrazoles was performed.
• Mechanisms explaining the formation of bicyclic and tricyclic compounds were discussed.

Perfluoroalkylated hydrazones 1a–e were prepared from diethyl hydrazinophosphate and were engaged in the reaction with 3-substituted homoallenyl aldehydes according to Zwierzak's 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.

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