Radical-mediated deiodination

Radical-mediated deiodination, methanolysis of the acetate and subsequent oxidation of the resulting alcohol furnished the ketone 43 in 87% total yield. Transformation of 43 into the corresponding cyanohydrin acetate under ordinary conditions resulted in the formation of a diastereomeric mixture 44 and 45. However, only the kinetically favored cyanohydrin acetate 44 was obtained when treated with hydrogen cyanide and pyridine. Treatment of the nitrile 44 with HCl gas afforded the amide 46, which was subjected to alkaline hydrolysis followed by esterification of the resulting carboxyhc acid with diazomethane to furnish 5 in 11% overall yield from 27. 

The applicability of tin-mediated radical cyclizations of non-isocyanides to form indoles has been pursued by several other investigators. Uneyama and colleagues reported the tin-mediated deiodination of imidoyl iodides and subsequent indolization (Scheme 1, equation 1) [1], This radical cyclization is also effected photochemically. Bowman and colleagues exploited the tin-promoted radical generation from imidoyl selanides and cyclization to form indoles... 

Crich and Rumthao reported a new synthesis of carbazomycin B using a benzeneselenol-catalyzed, stannane-mediated addition of an aryl radical to the functionalized iodocarbamate 835, followed by cyclization and dehydrogenative aromatization (622). The iodocarbamate 835 required for the key radical reaction was obtained from the nitrophenol 784 (609) (see Scheme 5.85). lodination of 784, followed by acetylation, afforded 3,4-dimethyl-6-iodo-2-methoxy-5-nitrophenyl acetate 834. Reduction of 834 with iron and ferric chloride in acetic acid, followed by reaction with methyl chloroformate, led to the iodocarbamate 835. Reaction of 835 and diphenyl diselenide in refluxing benzene with tributyltin hydride and azobisisobutyronitrile (AIBN) gave the adduct 836 in 40% yield, along with 8% of the recovered substrate and 12% of the deiodinated carbamate 837. Treatment of 836 with phenylselenenyl bromide in dichloromethane afforded the phenylselenenyltetrahydrocarbazole 838. Oxidative... 

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