Mechanism of SmI2 Reduction of 5-Bromo-6-oxo-6-phenylhexyl Methanesulfonate Studied by Spin Trapping with 2-Methyl-2-nitrosopropane.

The radical formed by reduction of 5-bromo-6-oxo-6-phenylhexyl methanesulfonate, an α-bromoketone, with SmI2 was spin trapped with 2-methyl-2-nitrosopropane. Electron paramagnetic resonance spectra of the spin adduct and the adduct formed in the analogous reaction with selectively deuterated substrate identify the radical intermediate in this SmI2 reduction as a carbon-centered radical. This result supports the proposal that the formation of reactive Sm-enolates arises from reduction of the carbon-bromine bond rather than a ketyl radical anion.