反应详情

Reaction of the commercially available 2,6-dichloropurine (3) with benzylamine gave 2-chloro-6-benzylaminopurine (4) using a reported procedure. Under our conditions, the reaction was complete in 15 min at 60° C. instead of the reported time of 3 h at 110° C. Propargylation of compound 4 using propargyl bromide in DMSO under mild conditions gave 2-chloro-6-benzylamino-9-(2-propynyl) purine (5) regioselectively in high yield. The Cu(I) catalyzed azide-alkyne click reaction (the Sharpless-Huisgen 1,3-dipolar cycloaddition) of the alkyne 5 with fluorinated benzyl azides, prepared in situ from their corresponding benzyl bromides, gave exclusively 1,4-disubstituted triazoles, 7-9. The isomeric homogeneity of the product triazoles was readily verified through their 19F NMR spectra. The pentafluorophenylmethyl-triazole, 9, showed relatively shielded δ19F absorptions as compared to the o-fluorophenylmethyl- and the 2,6-difluorophenylmethyl-triazoles, 7 and 8 respectively, in accordance with similar observations for the monofluoro-, difluoro-, and pentafluorotoluenes.