Regioselective N-alkylation of some 2 or 6-chlorinated purine analogues

Imidazopyrimidines have some interconvertible tautomeric forms. Regioselectivities were resolved for N-benzylations of some 8-(substituted phenyl)chloropurines with benzyl or 4-chlorobenzyl bromides under basic conditions (K2CO3) in DMF. It was observed that, while N-benzylation of 2-chloro-8-(4-substituted)phenylpurines occur on the five-membered imidazole ring (1a, 1b, 2a and 2b) to the contrary, same alkylation reaction of 6-chloro 8 (4 fluorophenyl)purine (3) occurs on the six-membered pyrimidine ring (4). Their structures were established by combination of H-1-H-1 NOE (Nuclear Overhauser Effect Spectroscopy, NOESY) and H-1-C-13/N-15 HMBC (Heteronuclear Multiple Bond Correlation) methods. X-ray crystallographic data of compound 4 was also used for further confirmation. (C) 2022 Elsevier B.V. All rights reserved.