Final answer:
For high-yielding arylation of purine nucleosides, Qu and coworkers utilized Pd(OAc)2/AgOAc/AcOH with iodobenzene under an N2 atmosphere at 120 °C to achieve selective arylation at the ortho position. Different catalyst systems and conditions alter the regioselectivity and yield of the reaction.
Step-by-step explanation:
To accomplish a high yield transformation in organic synthesis, the selection of appropriate reaction conditions is crucial. In the context provided, Pd-catalyzed C-H activation is utilized for regioselective arylation of purine nucleosides. Qu and coworkers achieved selective arylation at the ortho site of the C6-phenyl ring with conditions Pd(OAc)2/AgOAc/AcOH. Notably, for the arylation of 6-arylpurine nucleosides (e.g., compound 49) to produce compound 50, it was essential to perform the reaction under an inert N2 atmosphere at 120 °C with a large excess of iodobenzene and acetic acid (AcOH), leading to an excellent yield of 85%.
Alternative conditions are also mentioned where Pd(OAc)2/piperidine results in exclusive arylation at a different position, and the use of Pd(OAc)2/Cs2CO3 leads to double arylation or the formation of dimers. These examples demonstrate the significance of catalyst choice, ligand, solvent, and additive in dictating the regioselectivity and efficiency of the arylation process in organic chemistry.