Homoenolates radicals

No other synthetic method Is known that achieves the equivalent transformation. Rather elaborate procedures using an allylic anion type of the homoenolate "equivalents" or homoenolate radicals have been reported, but their tolerance to the structure of the enone acceptor is much narrower. 

A highly intriguing isomerization of the homoenolate radical which probably proceeds via formation of a cyclopropyloxy radical, was noted in the reaction of a mercurio aldehyde [37]. The product ratio should reflect the ratio of internal/ external trapping, and in fact the ratio of unrearranged and rearranged product depends on the concentration of the trapping reagent, Eq. (37). 

When the stabilities of the two corresponding radicals are grossly different as in the case of gem-dimethyl homoenolate, one may obtain the product originating from the more stable homoenolate radical as the sole product, Eq. (38). A related isomerization reaction, albeit proceeding in the opposite direction, has often been recorded for anionic holmoenolates. 

The reaction of a mercurio ketone with NaBRt produces a radical species which can be trapped in situ by a reactive acceptor such as a vinyl ketone. - Treatment of a mixture of a mercurio ketone and an electron-deficient terminal alkene (or fumarate) in CH2Q2 with concentrated aqueous NaBH4 gives a conjugate adduct (Scheme 19). Isomerization of such a homoenolate radical, presumably via an intermediate cyclopropanoxy radical, has been observed in the reaction of a mercurio aldehyde (Scheme 20).37.38 direction of the isomerization is opposite to that observed in the reactions of anionic ho-moenolates. Such a rearrangement has been used for a ring expansion reaction. ... 

The cyclopropanol also serves as a source of homoenolate radical species. Treatment of a mixture of the cyclopropanol and an enol silyl ether with manganese(III) 2-pyridinecarboxylate in DMF gives a 1,5-dicarbonyl compound (eq 15). ... 

Generation of Homoenolate Radicals. The homoenolate radical produced by Cerium(IV) Ammonium Nitrate (CAN) undergoes a fast oxidative addition to electron-rich alkenes such as... 

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