Yield:957478-22-7 82%

Reaction Conditions:

Stage #1: 3-nitro-1H-pyrazolewith sodium hydride in N,N-dimethyl-formamide; for 0.5 h;
Stage #2: 4-chlorobenzyl bromide in N,N-dimethyl-formamide; for 2 h;

Steps:

25

To a solution of 3-nitro-1H-pyrazole (prepared in example 3, 200 mg, 1.77 mmol) in anhydrous N,N-dimethylformamide (2 mL), a 60% dispersion of sodium hydride in mineral oil (92 mg, 2.30 mmol) was added while stirring under nitrogen. After the effervescence ceased and the mixture was stirred for additional 30 min, 4-chlorobenzylbromide (473 mg, 2.30 mmol) was added. The mixture was continued to stir under nitrogen for an additional 2 h. The solvent was removed in vacuo and purification by ISCO flash column chromatography (Teledyne Isco RediSep Flash Column 40 g; 2% methanol/methylene chloride to 5% methanol/methylene chloride) afforded 1-(4-chloro-benzyl)-3-nitro-1H-pyrazole (344 mg, 82%) as a white solid: H¹-NMR (400 MHz, CDCl₃) δ: 5.33 (2H, s), 6.90 (1H, d, J=2.3 Hz), 7.22 (2H, d, J=8.4 Hz), 7.34 (2H, d J=8.6 Hz), 7.40 (1H, d, J=2.6 Hz).

References:

US2008/21032,2008,A1 Location in patent:Page/Page column 36-37