Reactivity studies and application of protic-NHC complexes

Abstract

We used the previously synthesized Ru(II) based protic-NHC complexes to catalyze the acceptorless dehydrogenation of primary alcohols to carboxylic acids. We optimized the reaction conditions, using benzyl alcohol as the model substrate, and the best results of benzoic acid (93% isolated yield) were obtained with catalyst 2 (0.1 mol%) in 6h. The described process has been applied to a variety of substrates, including aliphatic alcohols, aromatic alcohols, and heteroaromatic alcohols, resulting in good yields of the desired carboxylic acids. The catalytic reaction exhibits an excellent functional group tolerance and operates via an acceptorless pathway for dehydrogenation, indicating that no external acceptor is required for the reaction to occur.