Ruthenium(II) Complexes with η6-Coordinated 3-Phenylpropanol and 2-Phenylethanol as Catalysts for the Tandem Isomerization/Claisen Rearrangement of Diallyl Ethers in Water

Abstract

A series of half-sandwich ruthenium(II) complexes containing η6-coordinated 2-phenylethanol and 3-phenylpropanol ligands, namely [RuCl2{η6-C6H5CH2(CH2)nCH2OH}(PR3)] (PR3 = PMe3, PPh3, P(OMe)3, P(OEt)3, P(OiPr)3, P(OPh)3; n = 0 (1a–f), 1 (2a–f)), have been investigated as catalysts for the tandem isomerization/Claisen rearrangement of diallyl ethers into γ,δ-unsaturated aldehydes using, for the first time, water as solvent. The best results in terms of activity and regioselectivity were obtained with the 3-phenylpropanol derivative [RuCl2(η6-C6H5CH2CH2CH2OH){P(OEt)3}] (2d). Thus, using only 1 mol % of this complex, in combination with NaOH (2 mol %), different diallyl ethers could be conveniently converted into the corresponding aldehydes in high yields and short times under relatively mild thermal conditions (100 °C).