1,1’-dibenzyl-5,5’-diphenyl-3,3’-bipyrazole

A mixture of 5,5’-diphenyl-3,3’-bipyrazole 1 (143 mg, 0.5 mmol) [1] and potassium tert-butoxide (112 mg, 1 mmol) in 20 mL of dry THF was stirred under reflux for 30 min [2]. After cooling the mixture to 0°C, the benzylbromide (171 mg, 1 mmol) in THF (5 mL) was then added drop by drop. After stirring under reflux for 3 h, the mixture was filtered and evaporated. The residue was purified on silica column (CH₂Cl₂) and recrystallized from ethanol, to give product 2 (0.17g, 73 % yield) as a white solid.

Melting point: 236 - 237°C (EtOH)

IR (KBr, cm^-1) : 3050 (ν_{C-H, arom.}); 1500 (ν_C=N); 1470 (ν_C=C); 1420; 1370; 1345; 1325; 1300 (δ_C-N); 1190; 1105; 1030; 945; 835; 820; 800; 750; 725.

¹H-NMR (CDCl₃, 300 MHz) : d= 7.34 - 7.33 (m, 12 H, H3’’’, H3’’, H4’’’ , H4’’); 7.25 (d, 4 H, H2 ’’, J = 8.8 Hz); 7.08 (d, 4 H, H2’’’, J = 8.5 Hz); 6.78 (s, 2 H, C4-H) ; 5.40 (s, 4 H, C₆H₅-CH₂).

¹³C-NMR (CDCl₃, 75 MHz) : d= 146.27 (C3); 145.55 (C5); 138.15 (C1’’’); 131.01 (C1’’); 129.12 (C3’’); 128.99 (C2’’); 128.92 (C3’’’); 128.81(C4’’); 127.69 (C4’’’); 127.05 (C2’’’); 104.78 (C4); 53.68 (CH₂).

MS (EI), m/z: 466 (35.3 %); 430 (0.1 %); 389 (9.0 %); 363 (29.8 %); 321(0.4 %); 277 (11.3 %); 105 (18.0 %); 91(100.0 %); 77(14.8 %); 51(6.4 %).