Synthesis of 8-Bromo-N-benzylpurines via 8-Lithiated Purines: Scope and Limitations

9-Benzylpurines have been lithiated in the 8-position and subsequently brominated when trapped with BrCCl₂CCl₂Br. The 8-bromopurines were isolated in excellent yields when the benzyl group carried an alkoxy or alkyl group in the ortho or para position. Without these substituents, the conversion was generally less, and formation of 8,8′-purinyl dimers was observed. There was also evidence of debenzylation in some instances. Bromination of 7-benzylpurines employing the same set of reaction conditions has also been achieved.