Purine Grignard reagent

Sugimura, H. Takei, H. Synthesis of 6-Alkylpurine Derivatives by Nickel Complex Catalyzed Coupling Reaction of 6-(Meth-ylthio)purine derivatives with Grignard Reagents. Bull. Chem. Soc. Jpn. 1985, 58, 664-666. 

Reaction of 9-benzyl-6-iodopurine 51, in toluene at -80 °C, with t-PrMgCl gave, almost quantitatively, the purine-derived Grignard reagent, which reacted selectively with aldehydes 52 affording the corresponding alcohols 53 in 25 to 62% yield <03OL4289>. 

A few purine ketones have been prepared including 8-acetyl- or 8-propionyl-caffeine from 8-cyanocaffeine and the appropriate Grignard reagent (56AP453). 

Nickel catalysts have been used in several reactions forming C-C bonds. Several different Grignard reagents alkylate the sp carbon of N-l,4-disubstituted purines and A(l)-substituted benzimidazoles in the presence of an Ni(dppp)Cl2 catalyst and 1,2-dichloroethane in THF (tetrahydrofuran) at room temperature. Yields range from 47 to 91%. Benzthiazole also reacts, but the yield is significantly lower. A possible mechanism is given. 

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