Nickel(II)–NΛNΛO Pincer Type Complex-Catalyzed N‑alkylation of Amines with Alcohols via the Hydrogen Autotransfer Reaction

A highly sustainable catalytic protocol for the coupling of alcohols and amines for selective monoalkylated amines using Ni­(II)–NΛNΛO pincer type complexes through the borrowing hydrogen methodology is described. An array of Ni­(II) catalysts (1–3) was synthesized and characterized by various spectral and analytical methods. Furthermore, the distorted square planar geometry of the complexes (1 and 2) was substantiated with single crystal X-ray diffraction study. The inexpensive nickel-based catalytic methodology displays a broad substrate scope for the N-alkylation of aromatic and heteroaromatic amines using a diverse range of primary alcohols with excellent yields up to 97%. The present approach is environmentally benign, which liberates water as the sole byproduct. A short synthesis of drug intermediates such as mepyramine and chloropyramine illustrates the utility of the present protocol.