Reactions of Benzenediazonium Ions with Guanine and Its Derivatives

Article abstract of DOI:10.1021/jo00342a014

Guanine reacts with several benzenediazonium ions rapidly in aqueous solution at pH 10.5 to form 8-(arylazo)guanines in good yield.The reaction of guanine with 4-bromobenzenediazonium ion forms ε-<(4-bromophenyl)azo>guanine about 50-fold more rapidly than the reaction of adenine with this ion to yield 6-<3-(4-bromophenyl)-2-triazen-1-yl>purine under these experimental conditions.Guanosine reacts much more slowly than guanine with the benzenediazonium ions in aqueous solution at pH 8.5 or 10.5 to give 8-arylguanosines.The structures of these products were established by their spectroscopic properties and by their quantitative conversion to 8-arylguanines. 5'-Guanylic acid also reacts quite slowly with the benzenediazonium ions in aqueous solution at pH 10.5.Only the compounds with strong electron-withdrawing groups yield N-2 triazenes at ambient temperature.No 8-aryl or 8-arylazo compounds are formed with 5'-guanylic acid at this temperature.However, 4-bromo- and 4-sulfobenzenediazonium ions react with 5'-guanylic acid at higher temperatures to yield the 8-aryl-5'-guanylic acids in low yield.The structures of these products were proven by hydrolysis to 8-arylguanines.The 8-arylguanosines and the 8-aryl-5'-guanylic acids are formed via free-radical phenylation reactions.The factors governing the reactivity of the adenines and the guanines are discussed.