Difluoromethyl radicals

However, better results have been reported when the polarity of the reaction is reversed. In this indirect path, an initial radical addition of a thio- or selenophenyl group affords a compound that can be the precursor of a difluoromethyl radical. This latter species can further add onto an activated double bond. These radical approaches have also allowed the synthesis of glycopeptides and difluorophosphonates (Figure... 

The kinetic data on the relative rate of the C—R bond homolytic cleavage from radical 30 relative to that of the C—CH3 bond reveal also the relative stability of fluoro-substituted methyl radicals to the methyl radical (Scheme 1.72). Mono- and difluoromethyl radicals were formed from 30 preferentially in comparison with methyl radicals. Here again, mono- and difluoro-substitutions in a-substituted methyl radicals seem to stabilize the radicals [29]. 

Tedder and Walton [286] reviewed the kinetics of the reactions of halogenomethyl radicals in 1967. As regards mono- and difluoromethyl radicals, most of the data given in Table 24 have been obtained since that time. The commercial availability of the corresponding ketones, difluoro-... 

Metathetical reactions of mono and difluoromethyl radicals transfer of hydrogen atoms... 

Murakami, S. Kim, S. Ishii, H. Fuchigami, T. Aromatic suhstitution with photochemi-caUy generated difluoromethyl radicals hearing electron-withdrawing group. Synlett 2004, 5, 815-818. 

Murakami S, Ishii H, Tajima T, Fuchigami T (2006) Photochemical substitution of olefins and aromatic compounds with difluoromethyl radicals bearing ester and phosphonate groups. Tetrahedron 62 3761-3769... 

Difluoromethyl radicals were produced by photo-initiated Se-CF2 bond cleavage of ethyl a,a-difluoro-a-(phenylseleno)acetate. Their reaction with thiophene gave the product of 2-difluoromethylation (Scheme 145) [209]. 

Difluoromethyl radical has been produced using excited mercury atoms as photosensitisers (15), but so far this... 

Table II shows a regular progression in the activation energy differences from the negative value for methyl radicals to the positive value for trifluoromethyl radicals with fluoromethyl and difluoromethyl radicals giving values in between.

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