3-Bromomethyl-1,5-diphenyl-1H-pyrazolo[4,3-e][1,2,4]triazine and 3-Dibromomethyl-1,5-diphenyl-1H-pyrazolo[4,3-e][1,2,4]triazine

As part of our research programme we have synthesized the title compounds as valuable intermediates for the preparation of acyclonucleosides-biologically active molecules. The starting material 1 was obtained according to the reported procedure [1] and title compounds were obtained using N-Bromosuccinimide (NBS) as brominating agent.

To a solution of 1 (72 mg, 0.25 mmol) in CCl₄ (10 ml) NBS (178 mg, 1mmol) and Azobis(isobutyronitrile) (AIBN) (17 mg, 0.1 mmol) were added. The mixture was refluxed for 4.5 h. The solvent was evaporated in vacuo and the residue was purified by column silica gel chromatography (silica gel 230-400 mesh, CHCl₃/n-hexane mixture 1:1) to give 99 mg (0.27 mmol, 54%) of 2 and 63 mg (0.14 mmol, 28%) of 3.

3-Bromomethyl-1,5-Diphenyl-1H-Pyrazolo[4,3-e][1,2,4]Triazine (2)

Melting Point: 185-187^oC

¹H-NMR (200 MHz, CDCl₃): δ= 8.67-8.72 (m, 2H); 8.41-8.46 (m, 2H); 7.55-7.65 (m, 5H); 7.42-7.46 (m, 1H); 5.02 (s, 2H).

IR (KBr, cm^-1): 3032; 1595; 1500; 1421; 1213; 1109; 1080; 753; 689.

MS- EI (m/z, %): 365 (6) [M⁺]; 339 (32); 337 (32); 286 (14); 259 (29); 258 (100); 218 (20); 155 (51); 115 (17); 77 (18).

HR-MS (EI, 70eV) Calculated for C₁₇H₁₂⁷⁹BrN₅: 365.02761. Found: 365.02685.

3-Dibromomethyl-1,5-Diphenyl-1H-Pyrazolo[4,3-e][1,2,4]Triazine (3)

Melting Point: 200-202^oC

¹H-NMR (200 MHz, CDCl₃): δ= 8.70-8.75 (m, 2H); 8.41-8.46 (m, 2H); 7.57-7.66 (m, 5H); 7.44-7.48 (m, 1H); 7.18 (s, 1H).

IR (KBr, cm^-1): 2922; 1593; 1500, 1420; 1108; 775; 690.

MS- EI (m/z, %): 445 (10) [M⁺]; 419 (29); 417 (58); 415 (29); 366 (23); 364 (22); 339 (32); 338 (100); 337 (32); 336 (98); 258 (37); 235 (38); 233 (40); 218 (14); 155 (10); 77 (30).

HR-MS- EI: Calculated for C₁₇H₁₂⁷⁹Br⁸¹BrN₅: 444.93607. Found: 444.93751.