Water → 6,7-Dihydro-5H-pyrazolo[5,1-b][1,3]oxazine-3-carboxylic acid

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Reaction Steps

A solution of 6,7-dihydro-5H-pyrazolo[5,1-b][1,3]oxazine-3-carboxylic acid ethyl ester (9.67 g, 49.3 mmol) in tetrahydrofuran (150 mL), ethanol (50 mL) and 1M of lithium hydroxide in water (148 mL, 148 mmol) was stirred at 60° C. for 2 days. After cooling, the volatiles were removed. The residue was transferred to an Erlenmeyer flask and ice was added. The reaction was acidified to pH 2 with 10M HCl. The aqueous layer was extracted several times with 3/1 chloroform/IPA. The combined organic layers were dried (Na2SO4), filtered, concentrated to afford the acid as a solid (8.14 g, 98%). 1H NMR (400 MHz, DMSO-d6) δ7.57 (s, 1H), 4.37 (t, 2H, J=5.29 Hz), 4.07 (t, 2H, J=6.11 Hz), 2.20-2.15 (m, 2H).

Provenance & Evidence