Cl.[C:2]([NH:6][NH2:7])([CH3:5])([CH3:4])[CH3:3].C([C:11](=[C:17]=[CH:18]N(C)C)[C:12]([O:14][CH2:15][CH3:16])=[O:13])(=O)C.[CH2:22](O)C>CCOCC>[C:2]([N:6]1[C:18]([CH3:22])=[CH:17][C:11]([C:12]([O:14][CH2:15][CH3:16])=[O:13])=[N:7]1)([CH3:5])([CH3:4])[CH3:3]In ethanol (5 mL) was placed the t-butylhydrazine hydrochloride (0.79 g, 6.3 mmol) and ethyl 2-acetyl-3-(dimethylaminomethylene)acrylate (1.0 g, 6.3 mmol). The mixture was refluxed for 8 hours. The mix was evaporated at reduced pressure to give an oil. The oil was dissolved in ether (25 mL) and washed successively with water (25 mL), saturated sodium bicarbonate (25 mL) and brine (25 mL) was dried (Na2SO4), concentrated in vacuo and purified by silica gel column chromatography (EtOAc/hexanes) to obtain ethyl 1-tert-butyl-5-methyl-1H-pyrazole-3-carboxylate (0.60 g, 45% yield). 1H NMR (400 MHz, DMSO-d6): δ 6.54 (s, 1H), 4.22 (q, J=7.2 Hz, 2H), 2.44 (s, 3H), 2.42 (s, 3H), 1.57 (s, 9H), 1.25 (t, J=7.2 Hz, 3H); MS (ESI) m/z: 211.1 (M+H+).
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