107862-65-7

5,6-Dihydro-4H-pyrrolo[1,2-b]pyrazole is used in the preparation of withasomnine molecules, pyrazole alkaloids, for their application towards antiinflammatory compounds and analgesics.

3-(3-Chloropropyl)-1H-pyrazole (500 mg, 3.5 mmol) was used as a starting material and dissolved in a mixed solvent of isopropanol/water (5 mL/1 mL) and potassium hydroxide (389 mg, 6.9 mmol) was added. The reaction mixture was stirred at 90 °C for 2 hours. After completion of the reaction, the mixture was cooled to room temperature and extracted with dichloromethane (3 x 20 mL). The organic layers were combined, dried with anhydrous magnesium sulfate, filtered and concentrated under reduced pressure. Purification of the residue by silica gel column chromatography (petroleum ether: ethyl acetate = 6:1 to 2:1) afforded 5,6-dihydro-4H-pyrrolo[1,2-B]pyrazole (150 mg, 39.6% yield) as a brown oil.LC-MS (ESI) detection: 109 [M + 1].

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