Catalytic isomerization of allylic alcohols by (eta(6)-p-cymene)-ruthenium(II) complexes in organic and aqueous media: New recyclable and highly efficient catalysts in water containing ammonium-functionalized ligands

The water-soluble complexes [RuCl2(eta(6)-p-cymene){kappa-(P)-PPh3-n(OCH2CH2NMe3)(n)}][SbF6](n) [n = 1 (4a), 2 (4b) or 3 (4c)] have been prepared from the neutral precursors [RuCl2(eta(6)-p-cymene){kappa-(P)-PPh3-n(OCH2CH2NMe2)(n)}] [n = 1 (2a), 2 (2b) or 3 (2c)] and MeI via quaternization of the nitrogen atom of the terminal aminoalkyl groups, and subsequent counteranion exchange by the treatment with AgSbF6. Complexes 2a-c and 4a-c have proven to be highly active catalysts for isomerization of allylic alcohols in THF and aqueous media, respectively. Moreover, the water-soluble catalysts 4a-c can be reused after a simple extraction process at the end of the reaction. In particular, 4c presents a remarkable capability to be recycled, being active during 10 successive runs.