Convenient synthesis of symmetrical azines from alcohols and hydrazine catalyzed by ruthenium(II) hydrazone complex in air

A tandem approach to synthesize symmetrical azines from alcohols and hydrazine hydrate catalyzed by new Ru(II) hydrazone complex was reported. A diverse range of azines was synthesized in good yields using 1 mol % of catalyst. Remarkably, the catalytic reactions operate under aerobic and mild reaction conditions with the release of water as the by product. [Display omitted] •Synthesize of azines from alcohols and hydrazine hydrate catalyzed by Ru(II) hydrazone complexes was reported.•A diverse range of azines was synthesized in good to high yields using 1 mol % of catalyst loading.•The catalytic reactions operate under aerobic condition with the release of water as the by product. New ruthenium(II) complexes (1–4) were synthesized from the reaction of ligands namely 10-(2-(benzothiazol-2-yl)hydrazano)phenanthren-9(10H)-one (BTPQ) or 10-(2-(quinolin-2-yl)hydrazano)phenanthren-9(10H)-one (QHPQ) with [RuHCl(CO)(EPh3)3] (E = P or As) under reflux. The formation of the complexes was confirmed by analytical and various spectral methods including single crystal XRD analysis. The synthesized complexes were applied as catalysts for the synthesis of symmetrical azines from alcohols and hydrazine hydrate under air. Different substituents in alcohols were well tolerated and wide spectrum of azines were synthesized in good to excellent yields using 1 mol % of catalyst loading. The aerobic catalytic reaction releases environmentally benign H2O is the only byproduct. Moreover, a plausible mechanism has been provided for the Ru-catalyzed azine synthesis.