Ruthenium(II) Complexes with eta(6)-Coordinated 3-Phenylpropanol and 2-Phenylethanol as Catalysts for the Tandem Isomerization/Claisen Rearrangement of Diallyl Ethers in Water

A series of half-sandwich ruthenium(II) complexes containing eta(6)-coordinated 2-phenylethanol and 3-phenylpropanol ligands, namely [RuCl2{eta(6)-C6H5CH2(CH2)(n) CH2OH}(PR3)] (PR3 = PMe3, PP3, P(OMe)(3), P(OEt)(3), P(OEt)(3), P(OPh)(3) ; n = 0 (1a-f, (2a-f), have been investigated as catalysts for the tandem isomerization/Claisen rearrangement of diallyl ethers into gamma,delta-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 (eta(6)-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 degrees C).