Benzylic hydroperoxide rearrangement

The rate appears to be slower in the presence of hydroquinone, suggesting a radical chain mechanism for the rearrangement of MCH to toluene (6b). (In t ie presence of oxygen, the product of the reaction is benzyl hydroperoxide (6b). ) However, it is difficult to find an inhibitor that produces a radical that does not abstract hydrogen from the super-reactive MCH. (For example, DPPH and galvinoxyl destroy MCH, and of course styrene cannot be used as an inhibitor.) Thus, it is difficult to prove that the rearrangement involves a radical chain. 

AUyl transfer reactions, 73, 1 Allylic alcohols, synthesis from epoxides, 29, 3 by Wittig rearrangement, 46, 2 Allylic and benzylic carbanions, heteroatom-substituted, 27, 1 Allylic hydroperoxides, in... 

On an industrial scale, phenol is obtained by the oxidation of isopropylbenzene (cumene). Initially a hydroperoxide is formed, which then undergoes a fragmentation and rearrangement. The initial oxidation illustrates the susceptibility of benzylic positions to oxidative, particularly radical, attack (Scheme 4.14). 

Oxidative rearrangements. In the presence of an acid, C, -diarylaldimines give A(,A(-diarylformamides. Benzylic alcohols form the corresponding hydroperoxides, which split off the alkyl residue to furnish phenols by the well-known rearrangement pathway. 

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