Pierre Dizabo

Homogeneous oxidation of oct-1-ene by dioxygen or t-butyl hydroperoxide catalyzed by rhodium(III) or palladium(II) species: studies with 18O2 and [2-2H] oct-1-ene

Abstract Rhodium(III), rhodium(I) or palladium(II) chloro complexes serve as homogeneous precursors for the oxidation of oct-1-ene with 18 O 2 and of [2- 2 H]oct-1-ene with 16 O 2 . Incorporation of labelled dioxygen into the product alkanone can be obtained from the ‘H-M/ 18 O 2 /C 6 H 6 ’ (M = Rh III or Pd II ) stoichiometric systems. The oxidation of olefin becomes catalytic only in the presence of oxidizable alcohols, but solvent co-oxidation leads to 18 OH 2 . Subsequent reaction gives 16 OH 2 and 1,1-diethoxyethane. The results show that the isotope label in the ketone is washed out by exchange with the catalytic medium. Deuterium transfer in the oxidation of [2- 2 H] oct-1-ene is studied. Results involving [CF 3 COOPd-OOt-Bu] 4 and ‘RhCl 3 /t-BuOOH’ systems are also reported. Solvents (ethanol or benzene) are responsible for partial deuterium loss. Two mechanistic schemes for the conversion of postulated pseudo-peroxometallocycles to ketones are proposed. H/D exchange of olefinic hydrogen with ethanol (EtOD or EtOH) can proceed via formation of hydrido complexes.