Arylations Using Nucleophilic C-Centered Radicals

The tin hydride-mediated C(sp )-C(sp )-bond formation has successfully been applied as key step in the synthesis of various natural products. Amaiyttidacaea alkaloids [39], glaucine [40], cryptopleurine ]41] and an anticancer benzo]c]phenanthridine alkaloid [42] were each successfully prepared using this approach. 

Interestingly, the intramolecular radical addition onto arenes [49] and heteroarenes [50-54] can also be performed with primary and secondary alkyl radicals. As for the aryl radicals discussed above, the alkyl radicals used in these arylations are usually generated from the corresponding bromides or iodides using Bu3SnH and a radical initiator. Bowman has carefully studied the intramolecular radical 

Furthermore, iminyl radicals have been used in intramolecular homolytic aromatic substitutions. The iminyl radicals can be generated in situ by C-radical addition onto nitriles [55] or they may be generated directly from the corresponding oximes [56] and hydrazones [57]. 

Along with tin hydride-mediated arylations, electrochemical [61], photochemical [62] and iodine transfer methods [63] have each been successfully used for the generation of alkyl radicals in homolyhc aromahc subshtuhons. Moreover, nucleophilic a-oxyalkyl radicals, prepared from the corresponding aldehydes by treatment with either samarium diiodide [64] or stannyl radicals [65], reacted with arenes to afford the homolyhc subshtuhon products. In a series of reports, Zard highlighted the potenhal of xanthates as alkyl radical precursors in homolytic aromatic subshtuhons [66]. 

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