Oxidation of Non-functional Carbon Atoms

The allylic oxidation with derivatives of chromic add (K.B. Wiberg, 1965 H.G. Bosche, 1975), e.g. di-t-butyl chromate (K. Fujita, 1961), CrOj/pyridine (W.G. Dauben, 1969), or KjCr04 (C.Y. Cuilleron, 1970), gives similar products in occasionally very high yields. 

Alkyl groups attached to aromatic rings are oxidized more readily than the ring in alkaline media. Complete oxidation to benzoic adds usually occurs with nonspecific oxidants such as KMn04, but activated tertiary carbon atoms can be oxidized to the corresponding alcohols (R. Stewart, 1965 D. Arndt, 1975). With mercury(II) acetate, allylic and benzylic oxidations are also possible. It is most widely used in the mild dehydrogenation of tertiary amines to give, enamines or heteroarenes (M. Shamma, 1970 H. Arzoumanian, 1971 A. Friedrich, 1975). 

The a-oxidation of carbonyl compounds may be performed by addition of molecular oxygen to enolate anions and subsequent reduction of the hydroperoxy group, e.g. with triethyl phosphite (E.J. Bailey, 1962 J.N. Gardner, 1968 A,B). If the initially formed a-hydroperoxide possesses another enoiizable a-proton, dehydration to the 1,2-dione occurs spontaneously, and further oxidation to complex product mixtures is usually observed. 

Vedejs (1978) developed a general method for the sterically controlled electrophilic a-hydroxylation of enolates. This uses a bulky molybdenum(VI) peroxide complex, MoO(Oj)2(HMPTA)(Py), which is rather stable and can be stored below 0 °C. If this peroxide is added to the enolate in THF solution (base e.g. LDA) at low temperatures, one O—O bond is broken, and a molybdyl ester is formed. Excess peroxide is quenched with sodium sulfite after the reaction has occurred, and the molybdyl ester is cleaved to give the a-hydroxy car- 

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