Ruthenium(II) Complexes with η⁶‑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 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).