Ru(dppbsa)-catalyzed hydrodeoxygenation and reductive etherification of ketones and aldehydes

Methods for the Ru(dppbsa)-catalyzed hydrodeoxygenation and reductive etherification of ketones and aldehydes were developed. Carbonyl substrates without β-CH functionality follow a hydrogenation-hydrogenolysis path, wherein the hydrogenolysis of the alkanol intermediates is the rate-limiting step. By contrast, a hydrogenation-dehydration-hydrogenation path is followed by carbonyl substrates with β-CH functionality, suffering from rate-limiting sulfonate ligand-assisted reversible H₂ cleavage. This hydrodeoxygenation is competitive with reductive etherification when using alkanols as hydrogen surrogates. The chemoselectivity can be adjusted based not only on the bond strengths of O-H and C-H bonds in the alkanols but also on the steric hindrance of the carbonyl substrates. As a result, both hydrodeoxygenation and reductive etherification exhibit excellent aldehyde tolerance, while the reductive etherification of ketones is highly hindered based on this protocol.