Free radicals rearrangements

Scheme 12.6 gives some examples of reactions in which free-radical rearrangements have been observed. 

Scheme 3.4. Walton s and McCarroll s classification of unimolecular free-radical rearrangements.

An excellent review by Walton and McCarroll has recapitulated the various processes which can be featured during a radical cascade [2]. Moreover, these authors have elaborated a compilation of classes of unimolecular free-radical rearrangements, as illustrated in Scheme 3.4. 

Beckwith, A.L.J, and Ingold, K.U. (1980). Free Radical Rearrangements. In Rearrangements in Ground and Excited States, Vol. 1, 161. Academic Press... 

Wallace, T. J., and R. J. Gritter The Free Radical Chemistry of Cyclic Ethers. III. A Free Radical Rearrangement Reaction. J. org. Chem. 27, 3067 (1962). 

Brown, H. C., and G. A. Russell The photochlorination of 2-methyl-propane-2-d and a-d1-toluene the question of free radical rearrangement or exchange in substitution reactions. J. Amer. chem. Soc. 74,3995 (1952). 

II/III Free radical rearrangements, including Si2Me6 — Me3SiSiMe2CII2 Me3SiCIT2SiMe2 191... 

Phenylpropanoic, 4-phenylbutanoic and 3,3-diphenylpropanoic acids were transformed with xenon difluoride to the corresponding fluorinated products without indication of free-radical rearrangement or cyclization, while phenylacetic acid in the presence of benzene produced diphenylmethane, indicating the involvement of a trivalent species (Scheme 44). Trifluoromethylbenzene was formed in 42% yield by reaction of trifluo-roacetic acid with benzene35-37. 

Free radical rearrangements 6 Nitrogen-centered radicals 7 Nitroxyl radicals 7 Aryloxy radicals 8 Sulfur-centered radicals 8 Ketyl radicals 9 Radical cations and anions 10... 

Wollowitz, S., and Halpem, J., 1984, Free-radical rearrangement involving the 1,2-migration of a thioester groupoModel for the coenzyme-B12 dependent methylmalonyl-CoA mutase reaction, J. Am. Chem. Soc. 106 831998321. 

Free-radical rearrangements are much less common than the nucleophilic type previously considered, for the reasons mentioned on p. 1559. Where they do occur, the general pattern is similar. There must first be generation of a free radical, and then the actual migration in which the migrating group moves with one electron ... 

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