Self-coupling of benzylamines over a highly active and selective supported copper catalyst to produce N-substituted amines by the borrowing hydrogen method

•Self coupling of primary amines to produce the secondary amine via borrowing hydrogen methodology.•Highly efficient catalysis by alumina-entrapped Cu nanoparticles.•Self coupling of benzyl amine over the established copper catalyst produces >90% dibenzylamine.•Process does not require external hydrogen.

Amines were used as hydrogen donor for the borrowing hydrogen methodology with a heterogeneous catalyst. Supported copper catalysts catalyzed the self-condensation reaction of primary amines to secondary amines/imines with high efficiency. The recyclable, non-leaching catalyst is synthesized by a sol–gel method, which allows entrapping copper nanoparticles in an alumina matrix. The synthesized copper catalysts were found to be active in the self-coupling of primary amines to produce secondary amines. The hydrogen donor for the transfer hydrogenation appears to be the primary amine, and no additional hydrogen or hydrogen transfer reagent is required. To the best of our knowledge, this is the first report of a copper based catalyst for this type of reaction using the borrowing hydrogen scheme.

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