| In chapter 1, we describe development of a mild and efficient method for SNAr iodination of 6-chloropurine 2'-deoxynucleosides and nucleosides. Our studies demonstrate that 6-iodopurine nucleosides are excellent substrates for certain transition metal-catalyzed cross-coupling reactions.; In chapter 2, we describe synthesis of protected 6-fluoro, 6-chloro, 6-bromo and 6-sulfonylpurine nucleosides. Comparisons among 6-fluoro-, 6-chloro-, 6-bromo, 6-iodo and 6-sulfonylpurine nucleosides for SNAr reactions with various N, O and S nucleophiles were investigated. Our results demonstrate that the 6-fluoropurine nucleoside is the best substrate for SNAr reactions among the four 6-halopurine nucleosides with oxygen, sulfur and aliphatic amine nucleophiles, and also with an aromatic amine plus TFA as a catalyst. However, the 6-iodopurine nucleoside is the best substrate for the aromatic amine without acid. With oxygen and sulfur nucleophiles, the 6-sulfonylpurine nucleoside reacted even faster than the 6-fluoropurine nucleoside.; In chapters 3 and 4, nickel- and palladium-based systems with imidazolium-carbene ligands can catalyze efficient Suzuki cross-couplings of arylboronic acids and 6-[(imidazol-1-yl)-, (1,2,4-trizaol-4-yl), fluoro, alkylsulfanyl and alkylsulfonyl]purine 2'-deoxynucleosides and nucleosides to give the corresponding 6-arylpurine products. |
