Catalytic oxidations of alcohols

Abstract

The scope and mechanisms of catalytic methodologies for the selective oxidation of primary and secondary alcohols, using dioxygen, hydrogen peroxide or alkyl hydroperoxides as the stoichiometric oxidant, are critically reviewed Emphasis is placed on homogeneous transition metal catalysts. Catalytic oxidations with dioxygen generally involve late transition elements, e.g. Ru, Pd and Cu that operate via β-hydride elimination from a low-valent alkoxymetal intermediate (hydridometal mechanism) as the key step. In contrast, catalytic oxidations with hydrogen peroxide and alkyl hydroperoxides generally involve early transition metals, e.g. Ti, Mo, W and Re, and high-valent peroxometal complexes or first-row elements (V, Mn and Cr) and high-valent oxometal species as the active oxidant, respectively. Ruthenium forms an exception in that it is able to catalyze the aerobic oxidation of alcohols via a hydridometal or an oxometal mechanism.