Unexpected [4 + 2] Cycloaddition through Chromium Non-Heteroatom-Stabilized Alkynyl Carbene Complexes: Regioselective
Aránzazu Gómez1, Ignacio Funes-Ardoiz2, Diego Sampedro2
1Departamento de Química Orgánica e Inorgánica e Instituto Universitario de Química Organometálica "Enrique Moles" , Unidad Asociada al C.S.I.C. Universidad de Oviedo , C/Julián Clavería 8 , 33006 Oviedo , Spain.
Abstract:
A formal [4 + 2] heterocycloaddition of non-heteroatom-stabilized alkynyl carbene complexes and iminopyrroles is described. The reaction implies a totally regioselective synthesis of 6-azaindole derivatives through the formation of the pyridine ring. The mechanism of the reaction has been explored by means of density functional theory calculations, which showed a preference for the [4 + 2] cycloaddition instead of the [2 + 2] or [3 + 3] cycloadditions observed with other imines. The structure of the products also shows an unusual connectivity pattern from carbene complexes.
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