Ruthenium(II)-Catalyzed Transfer Hydrogenation of Aromatic and Heteroaromatic Aldehydes in Air

Abstract

Aromatic and heteroaromatic aldehydes are efficiently reduced to their corresponding alcohols in the presence of [RuCl₂(p-cymene)]₂ and KOAc in 2-propanol under air at 80 °C. The presence of KOAc in the reaction is essential; in its absence no reduction takes place. A highly efficient, external-base-free reduction of aldehydes has also been reported with (η⁶-arene)ruthenium(II) complexes containing O^O chelate ligand such as [Ru(OAc)₂(p-cymene)] and [RuCl(KA)(p-cymene)], obtaining alcohol in excellent yield (OAc, acetate; KA, kojic acetate). The scope of the reaction has been extended to a broad range of aromatic and heteroaromatic aldehydes.

GRAPHICAL ABSTRACT

Keywords:

• Heteroaldehydes
• kojic acid
• potassium acetate
• 2-propanol
• reduction
• ruthenium catalysts
• spectroscopic data

SUPPORTING INFORMATION

General experimental procedures, characterization data (¹H, ¹³C NMR, and HRMS) for alcohols, and copies of ¹H and ¹³C NMR spectra for selected alcohols for this article can be accessed on the publisher’s website.