OXIDATIVE CLEAVAGE OF EPOXIDES BY MOLYBDENUM(VI) PEROXO COMPLEXES

The oxidation of a series of epoxides by two molybdenum(VI) peroxo complexes MOO(O2)2L, [L = hexamethylphosphoric triamide (HMPT) and tridodecylphosphoric triamide (TDPT)], has been studied either under homogeneous stoichiometric conditions (DCE) or in a two-phase (H2O/DCE) catalytic (H2O2) system. The reaction involves the oxidative cleavage of the carbon-carbon bond of the oxirane ring, providing the corresponding carbonyl compounds in yields ranging from low to fair depending on the reaction conditions and the nature of the substrate. No evidence of the involvement of free radical species was obtained. The synthetic scope of such a transformation, occurring for both alkyl and aryl epoxides, is however limited by a concomitant decomposition of the oxidant which is triggered by the presence of the substrates. This suggests that a peroxo complex different form MoO(O2)2L, whose stability under the conditions adopted is rather high, is formed in solution where it undergoes significant decomposition. The nature of such a new species, likely resulting from the interaction between MoO(O2)2L and the epoxides, has not yet been elucidated.