The catalytic activity of a Ru complex 1, bearing a fused π‐conjugated imidazo[1,2–a][1,8]naphthyridine‐based mesoionic carbene (MIC) ligand, is examined for the oxidation of primary amines. Complex 1 affords nitrile or imine depending on the nature of the terminal oxidants and solvents used in the reactions. Primary amines are converted to nitriles using NaIO4 in EtOAc/H2O mixture, whereas imines are obtained under O2 balloon pressure in toluene. A variety of nitriles and imines are accessed with high yields and selectivity. A set of control experiments, reaction profiles, and kinetic studies are undertaken to disclose the mechanistic details for nitrile and imine formation. The catalytic reactions illustrate a subtle dependency on the choice of oxidants and solvents in the oxidation of primary amines.

Catalytic aerobic oxidation of primary amines to the amides, using the precatalyst [Ru(COD)(L1)Br2] (1) bearing an annulated π−conjugated imidazo[1,2−a][1,8]naphthyridine-based mesoionic carbene ligand L1, is disclosed. This catalytic protocol is distinguished...

A series of Mn(I) complexes Mn(L1)(CO)3Br, Mn(L2)(CO)3Br, Mn(L1)(CO)3(OAc) and Mn(L3)(CO)3Br [L1 = 2‐(5‐tert‐butyl‐1H‐pyrazol‐3‐yl)‐1,8‐naphthyridine, L2 = 2‐(5‐tert‐butyl‐1H‐pyrazol‐3‐yl)pyridine, L3 = 2‐(5‐tert‐butyl‐1‐methyl‐1H‐pyrazol‐3‐yl)‐1,8‐naphthyridine] were synthesized and fully characterized. The acid‐base equilibrium between the pyrazole and the pyrazolato forms of Mn(L1)(CO)3Br was studied by 1H NMR and UV‐vis spectra. These complexes are screened as catalysts for acceptorless dehydrogenative coupling (ADC) of primary alcohols and aromatic diamines for the synthesis of benzimidazole and quinoline derivatives with the release of H2 and H2O as byproducts. The protic complex Mn(L1)(CO)3Br shows the highest catalytic activity for the synthesis of 2‐substituted benzimidazole derivatives with broad substrate scope, whereas a related complex [Mn(L3)(CO)3Br], which is devoid of the proton responsive β‐NH unit, shows significantly reduced catalytic efficiency validating the crucial role of the β‐NH functionality for the alcohol dehydrogenation reactions. Control experiments, kinetic and deuterated studies, and density functional theory (DFT) calculations reveal a synchronous hydride‐proton transfer by the metal‐ligand construct in the alcohol dehydrogenation step.