Synthesis of Azirinyl Ethynyl Ketones and Their Use in the Preparation C(O)C≡CR-Substituted NH-Pyrroles/NH-Imidazoles and Azole–Azine/Azole–Azole Heterocyclic Hybrids

Azirinyl-substituted conjugated ynones were first synthesized by the reaction of lithiated acetylenes with 2H-azirine-2-carbonyl chlorides. Azirinyl ethynyl ketones containing only a C(O)C≡CR substituent at position 2 of the azirine ring are good precursors for obtaining α–C(O)C≡CR substituted NH-pyrroles and 5-[C(O)C≡CR]-substituted NH-imidazoles, reacting selectively only at the azirine moiety with 1,3-diketones and arylamidines, respectively. Various N-heterocyclic hybrids (pyrrole-pyrimidine, imidazole-pyrimidine, pyrrole-isoxazole, imidazole-isoxazole, pyrimidine-pyrrole-thiophene, pyrrole-pyrimidine-thiophene, imidazole-pyrimidine-thiophene, isoxazole-pyrrole-thiophene) have been prepared based on orthogonal or domino reactions of an azirine and C(O)C≡CR moieties of azirinyl ethynyl ketones.