Ruthenium-catalyzed estragole isomerization: high trans-selective formation of anethole

Abstract

Complexes [RuCl₂(η⁶-C₆H₅OCH₂CH₂OH)(L)] (L = P(OMe)₃ (1a), P(OEt)₃ (1b), P(OⁱPr)₃ (1c), P(OPh)₃ (1d), PPh₃ (1e)) have shown to be efficient catalysts for the isomerization of estragole into anethole, the best activities being obtained in polar solvents (water, methanol, ethanol). Interestingly, a complete selectivity toward trans-anethole could be reached under smooth conditions (80 °C) and in very short times (5–15 min). The catalytic experiments have been performed both under conventional and microwave heating, reaction rates being significantly enhanced under the latter conditions.