Synthesis of tetra-substituted imidazoles and 2-imidazolines by Ni(0)-catalyzed dehydrogenation of benzylic-type imines.

Adrian Tlahuext-Aca, Oscar Hernández-Fajardo, Alma Arévalo, Juventino J García

Index: Dalton Trans. 43(42) , 15997-6005, (2014)

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Abstract

Ni(0)-catalyzed dehydrogenation of benzylic-type imines was performed to yield asymmetrical tetra-substituted imidazoles and 2-imidazolines. This was achieved with a single operational step while maintaining good selectivity and atom economy. The catalytic system shows low to moderate tolerance for fluoro-, trifluoromethyl-, methyl-, and methoxy-substituted benzylic-type imines. In addition, the substitution pattern at the N-heterocyclic products was easily controlled by the appropriate selection of R-groups in the starting organic substrates. Based on experimental observations, we propose a reaction mechanism in which benzylic C(sp(3))-H bond activation and insertion steps play pivotal roles in this nickel-catalyzed organic transformation.