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Intramolecular reactions of N-nitrenes with alkynes: conformational anchoring in spiro-fused 2H-azirines
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1986
Year
Intramolecular ReactionsCross-coupling ReactionEngineeringHeterocyclicBiochemistryConformational AnchoringNatural SciencesSpiro CentreSpiro-fused 2H-azirinesStructure ElucidationOrganic ChemistryLead Tetra-acetateMain Group ChemistryChemistryHeterocycle ChemistryBiomolecular Engineering
Oxidation of N-aminoquinazolin-4(3H)-ones (7)–(11) with lead tetra-acetate in dichloromethane results in the intramolecular addition of the N-nitrene to the triple bond in each case and azirines (20), (22), (17), (23), and (30), respectively, are isolated with (31) identified as a by-product in the oxidation of compound (11). An X-ray crystal structure determination on compound (17) reveals a remarkable deformation of bond angles at the spiro centre and this feature appears to be common to all azirines. The five membered ring in the azirines (17), (20), (22), and (23) has the envelope conformation (26) and the six-membered ring in azirine (30) has the twist-boat conformation (32): a possible explanation for this conformational anchoring is offered.