Nitriles alkoxy radicals

Other examples of an attack on C from an alkoxy radical at C20 are recorded in the literature for instance, in the progesterone series the oxime (7) obtained from the photolysis of the corresponding nitrite was converted to the nitrile (8) J Oxidation and acid hydrolysis of the nitrile (8) gave 3,20-diketo-4-pregnen-18-oic acid (9) identical with a... 

Examples of the former take place when radical 234 is stabilized by a heteroatom. When Y is an alkoxy moiety, an oxonium is formed and trapped by several external nucleophiles [193]. When an amide was present on the starting material, as was the case with 235, amino sugars were obtained in good yields (68% for 238) [ 194]. Finally, when Y is an azide, oxidation to the a-azido cation delivers nitriles upon loss of nitrogen [195]. 

Photocyclisation of 8-alkoxy-l,2,3,4-tetrahydro-l-naphthalenones and 4-alkoxy-6,7,8,9-tetrahydro-5H-benzocyclohepten-5-ones gives naphtho[l, 8-bc]furans and cyclohepta[cd]benzofurans respectively, and conformational and substituent effects of 1,5-biradicals in the cyclisation process are discussed." " The same authors also describe substituent effects on the photocyclisation of ethyl 2-(8-oxo-5,6,7,8-tetrahydro-l-naphthyloxy)acetates and ethyl 2-(5-oxo-6,7,8,9-tet-rahydro-5H-benzocyclohepten-4-yloxy)acetates to give naphtho[l,8-bc]furans and cyclohepta[c,d]benzofurans respectively." Also reported are cyclisations involving photogenerated radical cations of unsaturated silyl enol ethers, fragmentation cyclisations of unsaturated ot-cyclopropyl ketones which occur by photoelectron transfer and give polycyclics, and kinetic and theoretical studies of [2+3] cycloadditions of nitrile ylids. These reactions have been studied mechanistically and their synthetic potential investigated. 

Carbon-centered radicals are nucleophilic or electrophilic species, depending upon the substituents at the radical center. Electron-donating substituents like alkyl or alkoxy groups increase the nucleophilicity - of the radicals whereas electron-withdrawing groups (EWG) like ester or nitrile groups increase their electrophilic nature . In nucleophilic radical reactions SOMO LUMO interaction dominates whereas electrophilic radical reactions are controlled by SOMO-HOMO interactions. 

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