F. Di Furia

Liquid phase oxidation reactions by peroxides in the presence of vanadium complexes

Abstract The reaction of vanadium (V) derivatives with hydrogen peroxide or with alkyl hydroperoxides leads to peroxovanadium complexes which are effective and selective oxidants of organic and inorganic substrates either under stoichiometric or catalytic conditions. Examples of synthetically significant oxidations of various classes of organic compounds are reported together with details on the commonly accepted mechanisms operating. When possible a comparison is made between peroxovanadium complexes of other do metal derivative, e.g. Ti(IV), Mo(VI) and W(VI).

Evidence of a SN2-SET continuum in the oxidation of organic sulfides by peroxovanadium complexes

The oxidation of di-n-butyl sulfide and phenylmethyl sulfide by two vanadium (V) peroxocomplexes, e.g. VO(O2)OCH3, 1, and VO(O2)(PIC)(H2O)2, 2, in methanol, was investigated. The kinetic analysis of the reactions revealed significant mechanistic differences between the two peroxometal oxidants. In particular, 1 behaves as an electrophilic oxidant so that the transition state of sulfide oxidations by 1 may be described as a SN2 displacement on the peroxide oxygen whereas 2 acts as a radical oxidant in a process which has a substantial SET character. The role of the picolinaoo ligand in determining the reactivtty of 2 is discussed in terms of a decrease of the electrophilicity of the peroxide oxygen compared with 1 and of a stabilization of the radical metal species.

Titanium-Promoted Enantioselective Oxidation of Thioethers and Synthetic Applications

Abstract The recent results of our studies on the asymmetric oxidation of alkyl and aryl thioethers by the Ti(IV)/(+)-diethyltartrate/alkylhydroperoxide reagent developed in our laboratories will be presented and their relevance in the understanding of the factors affecting the enantioselectivity of the process and in the synthesis of chiral synthons briefly discussed. A preliminary discussion on the structure of the reactive complex will also be presented.

Homolytic Reactivity of Peroxovanadium Complexes

Abstract The mechanism of the hydroxylation of aromatic hydrocarbons by V(V) peroxocomplexes will be discussed in the light of the results of a study of the ligand and solvent effect on the reaction. The intermediacy of a radical anion derived from VO(O 2 )PIC(H 2 O) 2 3 (PIC=picolinic acid anion) by one electron reduction is suggested as a likely pathway for the title process. Examples of its reactivity toward some model substrates are presented.

Oxidation of alcohols and diols by peroxometal complexes

Abstract The synthetic scope of the anionic oxo-diperoxo-molybdenum(VI) complex, MoO 5 PICO (PICO=Picolinate-N-Oxido anion), as selective oxidant of both primary and secondary alcohols and of diols to the corresponding carbonyl compounds, has been examined and some typical examples are presented. The mechanism of the oxidation has also been investigated and evidence is reported of an associative process with a substantial radical character.

Enantioselective Oxidation of Cyclic Dithioacetals and Dithioketals.

The asym. oxidation of a series of dithioacetals and dithioketals to their corresponding monosulfoxides is carried out using the procedure A) previously developed.