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Issue 25, 2016
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Catalytic transfer hydrogenation of azobenzene by low-valent nickel complexes: a route to 1,2-disubstituted benzimidazoles and 2,4,5-trisubstituted imidazolines

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Abstract

The one-pot synthesis of 1,2-disubstituted benzimidazoles by the transfer hydrogenation of azobenzene, using benzylamine as a hydrogen donor, sequential rearrangement of hydrazobenzene to semidine and further condensation with N-benzylideneamine is reported, catalyzed by 2 mol% of [Ni(COD)2] : dippe. The N2 substitution on benzimidazole can be controlled by the selection of different azobenzenes and C2 substitution will only depend on the chosen benzylamine. The current methodology avoids the addition of external oxidants, which are needed in the classical benzimidazole synthesis. In addition, the byproduct, N-benzylideneamine, obtained from dehydrogenation of benzylamine produced 2,4,5-trisubstituted imidazolines by cyclization and C–H functionalization, and this route was optimized with the use of 2 mol% of [Ni(COD)2] : 2PPh3.

Graphical abstract: Catalytic transfer hydrogenation of azobenzene by low-valent nickel complexes: a route to 1,2-disubstituted benzimidazoles and 2,4,5-trisubstituted imidazolines

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Publication details

The article was received on 28 Apr 2016, accepted on 20 May 2016 and first published on 23 May 2016


Article type: Paper
DOI: 10.1039/C6DT01674J
Dalton Trans., 2016,45, 10389-10401

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    Catalytic transfer hydrogenation of azobenzene by low-valent nickel complexes: a route to 1,2-disubstituted benzimidazoles and 2,4,5-trisubstituted imidazolines

    D. A. Zurita, M. Flores-Alamo and J. J. García, Dalton Trans., 2016, 45, 10389
    DOI: 10.1039/C6DT01674J

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