Efficient catalytic one‐step synthesis of substituted quinoline derivatives using newly synthesized Ru(II) half‐sandwich complexes of the type [Ru(η6‐p‐cymene)Cl(L)] (L = pyrrole‐2‐aldehydehydrazones) under mild conditions is described. The synthesized complexes exhibit excellent catalytic activity towards the coupling of 2‐amino alcohol with functionalized ketones and secondary alcohols in the optimal conditions and afforded the corresponding quinoline derivatives. The synthetic pathway proceeds with high atom efficiency via a sequence of acceptorless dehydrogenation and condensation steps. The maximum isolated yield of the product obtained was up to 97% using 0.3 mol% of catalyst loading for 5 h. These findings significantly advance the scope of the synthesis of bioactive heterocyclic compounds from readily available starting materials.