In this study, 6-chloropurines with varied substituents in the 2 and 9 or 7 positions were functionalized in the 8-position. This was done via lithiation and subsequent bromination to form 8-brominated purines.
It was observed that lithiation/bromination of N-9 benzylated purines bearing electron donating substituents on the phenyl ring gave good conversions and excellent yields of the expected 8-bromo purines. On the other hand, those bearing electron withdrawing groups on the phenyl ring gave poor conversions and yields of the expected 8-bromo purines.
Aside the expected 8-bromo purines, dimers and aldehydes were observed as by-products of this reaction.