Ru(II)‐p‐cymene complexes containing hydrazone ligands catalyzed α‐alkylation of ketones and one‐pot synthesis of bioactive quinolines and 3‐(quinolin-2-yl)‐2H‐chromen‐2‐one

Abstract

Ru(II)-arene complexes (1-4) containing salicylaldehyde based hydrazone ligands (L1-L4) have been synthesized and characterized. Molecular structure of complex 1 has been solved by single crystal X-ray crystallography. The ligands coordinated to Ru center through O and N atoms. Catalytic activity of all the complexes was tested in the α-alkylation of acetophenone with benzyl alcohol. Complex 1 showed better activity with the conversion of 97% under the optimized conditions. Then, using complex 1, scope of the reaction was extended to different aromatic ketones and primary alcohols. One pot synthesis of several bioactive quinolines was achieved using aromatic ketones and amino alcohols as coupling partners in the presence of complex 1 as a catalyst. Further, complex 1 catalyzed the one pot synthesis of 3-(quinolin-2-yl)-2H-chromen-2-one from 2-aminobenzyl alcohol and 3-acetyl coumarin, which led to a new synthetic approach for making this compound.