Potassium Carbonate → (S)-6-hydroxymethyl-2-phenoxymethyl-6,7-dihydro-5H-pyrazolo[1,5-a]pyrazin-4-one

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Reaction Steps

(S)-4-(5-Ethoxycarbonyl-3-phenoxymethyl-pyrazol-1-ylmethyl)-2,2-dimethyl-oxazolidine-3-carboxylic acid tert-butyl ester (0.91 g, 1.9 mmol) was dissolved in a 4M solution of HCl in dioxane (9.8 mL) and the solution was stirred at room temperature for 1 hour. The solvent was evaporated in vacuo and the residue was taken up in MeOH (10 mL) and K2CO3 (0.82 g, 5.96 mmol) was added. The mixture was stirred at 100° C. for 5 minutes under microwave irradiation. Then mixture was diluted with DCM. The solid was filtered off and the filtrate solvent was evaporated in vacuo. The residue was purified by flash column chromatography (silica, MeOH in AcOEt 0/100 to 10/90). Desired fractions were collected and the solvents evaporated in vacuo to yield (S)-6-hydroxymethyl-2-phenoxymethyl-6,7-dihydro-5H-pyrazolo[1,5-a]pyrazin-4-one (0.33 g, 61% yield) as an off-white solid. 1H NMR (400 MHz, DMSO-d6) δ ppm 3.27-3.33 (m, 1H), 3.46-3.54 (m, 1H), 3.73-3.84 (m, 1H), 4.30 (dd, J=13.4, 5.8 Hz, 1H), 4.38 (dd, J=12.9, 5.3 Hz, 1H), 5.05 (s, 2H), 5.18 (br. s., 1H), 6.77 (s, 1H), 6.91-6.98 (m, 1H), 6.99-7.07 (m, 2H), 7.25-7.35 (m, 2H), 8.26 (d, J=2.5 Hz, 1H).

Provenance & Evidence