Application of 2-hydrazino-1,3-benzoxazole_Kain Industrial Additive

Background and overview^[1]

2-Hydrazino-1,3-benzoxazole is an organic intermediate, which can be obtained by the reaction of 2-chlorobenzoxazole and hydrazine hydrate, and can be used to prepare a type of pyrazole compounds.

Preparation^[1]

Add a solution of 2-chlorobenzoxazole (2.5g, 16.3mmol) in dioxane (4mL) dropwise to NH₂H₄ H₂O (4.07 g, 81.4 mmol) in dioxane (20 mL). The temperature is below 30℃. The reaction mixture was stirred at 20°C for 1 hour. Evaporate the solvent. Water (50 mL) was added and the mixture was stirred for 10 minutes. The solid was collected by filtration, and the filter cake was washed with water (50 mL). The filter cake was dried to obtain pure product (2 g, yield: 82.4%) as a white solid. ¹H NMR (400MHz, DMSO-6) δ8.76 (br s, 1H), 7.31 (d, J = 7.7Hz, 1H), 7.22 (d, J = 7.3Hz, 1H) , 7.09 (dt, J= 1.0, 7.7Hz, 1H), 6.95 (dt, J= 1.1, 7.7Hz, 1H), 4.47 (brs, 2H).

Apply^[1]

2-Hydrazino-1,3-benzoxazole can be used to prepare pyrazole ring compounds.

A mixture of compound 2-hydrazino-1,3-benzoxazole (1g, 6.70mmol) and methyl 2,4-dioxopentanoate (966mg, 6.70mmol) in AcOH (5mL) Stir at 120°C for 16 hours. Evaporate the solvent. The crude product was purified by silica gel column chromatography (petroleum ether: ethyl acetate = 20:1-3:1) to obtain compound 238B (900 mg, crude product) as an off-white solid.

Main reference materials

[1] (WO2018064119) CALPAIN MODULATORS AND THERAPEUTIC USES THEREOF