Ruthenium-catalyzed one-pot synthesis of primary amides from aldehydes in water

The readily available arene–ruthenium(II) complex [RuCl2(η6-C6Me6){P(NMe2)3}] (5 mol%) proved to be an efficient catalyst for the direct synthesis of primary amides from aldehydes and hydroxylamine hydrochloride (NH2OH·HCl) in water at 100 °C. The process, which requires the presence of NaHCO3 to catch the HCl released during the formation of the key aldoxime intermediates, was operative with both aromatic, heteroaromatic, α,β-unsaturated and aliphatic aldehydes, and tolerated several functional groups. A greener approach using commercially available NH2OH solution (50 wt.% in water) is also presented.