Methyl radical nitrite esters

Alkoxy radicals are also the active hydrogen-abstracting species in a procedure that involves photolysis of nitrite esters. This reaction was originally developed as a method for functionalization of methyl groups in steroids.379... 

Cyclopropyl nitrites are considerably more reactive than other alkyl nitrites and readily rearrange below ice-bath temperatures.117) Thus, the nitrite ester of tetramethylcyclopropanone methyl hemiacetal is easily converted to the (3-propionate radical 149 at — 80 °C and, in the presence... 

There are a variety of photochemical reactions involving free nitrous oxide (NO) as persistent radical. Often there is an initial fragmentation, as presented in Scheme 6 for TV, 7V-dimethyl-/V-nitro-samine. One example is the Barton reaction of nitrite esters (Scheme 15). It allows the functionalization of methyl groups in steroids and utilizes an intermediate 1,5-hydrogen atom migration, which converts the initially formed oxygen-centered radical to a carbon-centered species.69... 

The Barton reaction (photolysis of a nitrite ester ) has been employed to attack C-4 methyl substituents in 4,4-dimethyl-5a-steroids. Nitrites of the 6a-and 6)3-alcohols (714) afforded alkoxyl radical species, which attacked the 4a-and 4/ -methyl groups respectively, giving the corresponding aldoximes e.g. 715). Yields were quite high (56—60%) from the 6a-ol and the 19-nor-6 -ol, but attack... 

Abbreviations BSO, D.L-buthionine-. i -sulfoxime L , lipid alkyl radicals LH, lipid LO, Upid alkoxyl radicals LOO, Upid peroxyl radicals L-NAME, yV -nitro-L-arginine-methyl ester MBl, methylene bridge index (mean number of h -aUytic methylene positions per fatty add) NO, nitric oxide NOS, nitric oxide synthase NO, nitrite N02, nitrogen dioxide NO2CI, nitryl chloride O2 , superoxide OH, hydroxyl radical OL, epoxyaUyhc radical OLOO, epoxyperoxyl radical 0=NOO , peroxynitrite SNAP, S-nitroso-iV-acetyl-D.L-penicillamine SOD, superoxide dismutase contd. onp. 98, Subcellular Biochemistry, Volume 36 Phospholipid Metabolism in Apoptosis. 

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