Efficient transformation of propargylic alcohols to α,β-unsaturated aldehydes catalyzed by ruthenium/water under neutral conditions

α,β-Unsaturated aldehydes were selectively obtained in high yields from propargylic alcohols in aqueous solutions using RuCpCl(PR3)2 (Cp=η5-C5H5) as a catalyst. Of the tert-phosphine ligands examined, PMe3 gave the most satisfactory results. Typically, RuCpCl(PMe3)2 (5 mol%) catalyzed the transformation of oct-1-yn-3-ol at 100°C to give 2-octenal in an isolated yield of 85% (E/Z=80/20).