Abstract

Aliphatic carboxylic acids represent a class of essential organic compounds. As some of the most fundamental and extensively utilized organic chemicals, they play irreplaceable roles across industry, daily life, biological systems, and materials science. Among numerous synthetic approaches to aliphatic carboxylic acids, transition metal-catalyzed direct synthesis from alcohols is particularly compelling, owing to its excellent step economy and environmental sustainability. Therefore, we developed a ruthenium(II)/diphosphine-catalytic system for the oxidation of primary alcohol with oxygen as terminal oxidant in water, providing a serious of aliphatic carboxylic acids in moderate to excellent efficiencies. Distinct from Ru(II)-catalyzed alcohol acceptorless dehydrogenation reactions that require stoichiometric bases, this transformation may proceed via a single-electron transfer mechanism in the absence of any additives. Furthermore, valence state changes of ruthenium and the diphosphine ligand were observed, with the in situ formed Ru(III)/Ru(IV) species identified as the actual catalytically active intermediates. The introduction of phosphine ligands increases the electron density of the ruthenium center, thereby facilitating the oxidation of low-valent ruthenium to high-valent ruthenium. This protocol provides an alternative reference for the one-step synthesis of carboxylic acids via low-valent metal-catalytic aerobic oxidation of primary alcohols.

Keywords Plus: SELECTIVE OXIDATION，EFFICIENT，DEHYDROGENATION，NANOPARTICLES，ALDEHYDES，KETONES，SALTS

Published in CHEMISTRY-A EUROPEAN JOURNAL；10.1002/chem.71246