Highly Efficient Rh(I) Homo- and Heterogeneous Catalysts for C-N Couplings via Hydrogen Borrowing

Rhodium(I) complexes were explored as catalysts for the hydrogen borrowing reactions of amines and alcohols. Bidentate carbene-triazole ligands were readily synthesized via click reactions which allowed a diversity of ligand backbones to be accessed. The catalytic transformations are highly efficient, able to reach completion in under 6 h, and promote C-N bond formation across a range of primary alcohol and amine substrates. Moreover, site-selective catalysis can be achieved using substrates with more than one reactive site. A rhodium(I) complex covalently attached to a carbon black surface was also deployed in the hydrogen borrowing coupling reaction of aniline with benzyl alcohol. This represents the first report of a heterogeneous rhodium catalyst used for hydrogen borrowing.