Arylation and Heteroarylation of Photochemically Generated Purinyl Radicals

Article abstract of DOI:10.1021/jo00144a023

Neutral purinyl radicals are new transient intermediates in nucleic acid chemistry.Photolysis of 9-substituted 6-iodopurines with ultraviolet light provides an excellent method for generating purin-6-yl radicals (or caged radical pairs), through homolysis of the weak carbon-iodine bond.The intermediacy of these radicals can be inferred from ESR data.When photolysis is carried out in the presence of benzene, the nascent purinyl radicals (or radical pairs) are intercepted and the corresponding 9-substituted 6-arylpurine is isolated.Heteroaromatic arylations also are possible.Thus, photolysis in the presence of N-methylpyrrole results in the formation of 9-substituted 6-(N-methylpyrr-2-yl)purine.Furan and thiophene derivatives also undergo photoarylation.The products are consistent with the preferred sites for radical attack upon these heteroaromatics.Reaction with diphenyl disulfide results in the formation of the corresponding purinyl thioether.