Organometallic Ru(III) Catalysts for α-Alkylation of Carbonyl Compounds using Alcohols: Mechanistic Insights via Detection of Key Intermediates.

Three novel cyclometalated ruthenium complexes ([Ru.L(9)] [Ru.L(10)] and [Ru.L(11)]) featuring azo functionalities were synthesized and characterized using a variety of spectroscopic techniques, namely FT-IR, electronic absorption spectroscopy, and ESI-MS. Representative solid-state structures of the acquired complexes were determined through X-ray crystallography. These complexes were evidenced to be efficient catalysts for the synthesis of various α-alkylated compounds utilizing simple acetophenone derivatives with easily affordable and economically viable alcohols, which were isolated and characterized via 1H and 13C NMR spectroscopy. The optimum reaction conditions were found by employing toluene as solvent, potassium tert-butoxide as base at 115 oC temperature utilizing 0.8 mol% of catalyst [Ru.L(10)]. The yield of the desired compounds found to be in the range of 83 - 97%. Additionally, mass spectrometry provided insights into the in-situ generated ruthenium hydride and ruthenium alkoxy intermediates, shedding light on the catalytic mechanism.