Desilylative radical alkylation

Desilylative radical alkylation via an electron transfer process... 

Another approach involves the use of an electron-poor olefin acting both as an absorbing electron acceptor and as a radical trap. In this case, a PET reaction between a cyclohexenone derivative and a silylated amine led to a radical ion pair. Desilylation of the silyl amine radical cation intermediate in polar protic solvent (e.g., MeOH) and subsequent aminoalkyl radical attack onto the enone radical anion yielded the alkylated cyclohexanones [23]. 

The unimolecular rates of reactions (Eqs. 8 and 9) were found to depend on solvent polarity and substituents on the aniline ring, nitrogen, and ot-carbon. The second-order rate constants for methanol-promoted desilylation (Eq. 10) of the aminium radical generated via SET reactions of a-anilinosilanes increased tenfold on changing the substituent on nitrogen from an alkyl group to acyl group. 

Laser flash photolysis techniques have been employed to evaluate the dynamics of decarboxylation reactions of cation radicals derived from a-aminocarboxylates. > In one report, variously substituted aminium radicals 47 were generated by laser flash excitation of anilinocarboxylates 46 (Scheme 21) in MeCN solutions containing the acceptor, 1,4-dicyanobenzene. These transients undergo fast, first-order decay by a pathway involving loss of carbon dioxide. The rate constants for decarboxylation were found to be in the range of 8 x 10 to 4 x 10 s . In addition, the rates show the same dependence on nitrogen, a-alkyl and a-phenyl substituents, as do the related a-CH deprotonation, a-desilylation, and retro-Aldol cleavage reactions. 

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