Catalytic oxidations of alcohols - Advances in Catalytic Activation of Dioxygen by Metal Complexes - page 143

groups. Reaction with the alcohol in the presence of a base, added as a
cocatalyst (NaOAc) or free ligand, affords a monomeric alkoxy
palladium(II) intermediate which undergoes elimination to give
the carbonyl compound, water and a palladium(0) complex. Oxidative
addition of dioxygen to the latter affords a palladium(II) complex
which can react with the alcohol substrate to regenerate the catalytic
intermediate, presumably with concomitant formation of hydrogen peroxide
as was observed in analogous systems 66 .
It is worth noting, in this context, that palladium complexes of
substituted phenanthrolines were recently shown 67 to catalyze the formation
of hydrogen peroxide, by reaction of a primary or a secondary alcohol with
dioxygen, in the presence of an acid cocatalyst, e.g. in a
biphasic chlorobenzene/water medium at 70°C and 5 bar. Turnover
frequencies up to were observed. The hydrogen peroxide is formed in
the organic phase, via palladium catalyzed oxidation of the alcohol, but is
subsequently extracted into the water phase where it is protected from
decomposition by the palladium complex. The same catalyst system was also
used for the production of hydrogen peroxide from a mixture of carbon
monoxide, water and dioxygen, with turnover frequencies up to
according to Reaction 17 68 .