1-(3-methylbutyl)-3-nitro-1H-pyrazole synthesis

Yield: 59%

Reaction Conditions:

Stage #1:3-nitro-1H-pyrazole with sodium hydride in N,N-dimethyl-formamide for 0.166667 h;
Stage #2:i-pentyl bromide in N,N-dimethyl-formamide at -25; for 20 h;

Steps:

43
3-Nitro-1H-pyrazole (prepared in example 3, 100 mg, 0.89 mmol) was dissolved in anhydrous N,N-dimethylformamide (4 mL) and a 60% dispersion of sodium hydride in mineral oil (42 mg, 1.06 mmol) was added while stirring under nitrogen. After the effervescence ceased and the reaction stirred for an additional 10 min before 1-bromo-3-methyl-butane (0.133 mL, 1.06 mmol) was added. The reaction continued to stir under nitrogen for 4 h. The reaction was stored at -25° C. for 16 h. The solution was diluted with ethyl acetate (30 mL), washed with water (2×10 mL), saturated aqueous brine solution (10 mL), dried over magnesium sulfate, filtered and concentrated in vacuo. Purification by ISCO flash column chromatography (Teledyne Isco RediSep Flash Column 40 g; 25% ethyl acetate/hexanes to 75% ethyl acetate/hexanes) afforded 3-nitro-1-iso-pentyl-1H-pyrazole (115 mg, 59%) as a clear oil.

References:

Berthel, Steven Joseph;Kester, Robert Francis;Murphy, Douglas Eric;Prins, Thomas Jay;Ruebsam, Frank;Sarabu, Ramakanth;Tran, Chinh Viet;Vourloumis, Dionisios US2008/21032, 2008, A1 Location in patent:Page/Page column 47