31037-02-2, Researchers who often do experiments know that organic synthesis is a process of preparing more complex target molecules from simple raw materials through one or more chemical reactions. Generally, it requires fewer steps, and cheap raw materials. 31037-02-2, name is Ethyl 5-amino-1-methyl-1H-pyrazole-4-carboxylate, A new synthetic method of this compound is introduced below.
Step 1. Synthesis of ethyl 5-bromo-1-methyl-1H-pyrazole-4-carboxylate Copper(II) bromide (99%, 20.0 g, 88.6 mmol) and tert-butyl nitrite (90%, 14.1 mL, 107 mmol) were combined in acetonitrile (65 mL) and heated to 65 C. Ethyl 5-amino-1-methyl-1H-pyrazole-4-carboxylate (10.0 g, 59.1 mmol) was slowly added portion-wise {Caution: gas evolution!} and the reaction was maintained at 65 C. for 24 hours. The mixture was cooled to room temperature, poured into aqueous hydrochloric acid (3 N, 600 mL), diluted with ethyl acetate (300 mL) and stirred for 10 minutes. The aqueous layer was extracted with ethyl acetate (150 mL), and the combined organic layers were dried over magnesium sulfate, filtered and concentrated in vacuo. The residue was purified via silica gel chromatography (Gradient: 5% to 100% ethyl acetate in heptane, with a 5-minute hold at 32%), affording the product as a pale yellow solid. Yield: 9.10 g, 39.0 mmol, 66%. LCMS m/z 233.3 (M+1). 1H NMR (500 MHz, CDCl3) delta 1.36 (t, J=7.1 Hz, 3H), 3.92 (s, 3H), 4.32 (q, J=7.1 Hz, 2H), 7.93 (s, 1H).
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