Selective Oxidation of Alcohol Function in Allylic Alcohols to α,β-Unsaturated Carbonyl Compounds Catalyzed by Zirconocene Complexes

Article abstract of DOI:10.1021/jo00231a006

Bis(η⁵-cyclopentadienyl)zirconium(IV) complexes, Cp2ZrH2 (1) and Cp2Zr(O-i-Pr)2 (4), in the presence of an appropriate hydrogen acceptor such as benzaldehyde or cyclohexanone catalyze the Oppenauer-type oxidation of allylic alcohols to α,β-unsaturated carbonyl compounds.For instance, primary allylic terpenoid alcohols, geraniol and nerol, were oxidized to α- and β-citrals, which are essential compounds in the perfumery industry, in substantial yields without any treatment.Similarly, secondary allylic alcohols such as 3-hexen-2-ol and 2-cyclohexen-1-ol were alsooxidized with ease to give 3-hexen-2-one and 2-cyclohexen-1-one in 93percent and 89percent yields, respectively.But the present OPP-type oxidation by zirconocene complexes is ineffective for propargylic alcohols.