Acetyl chloride → Acetic acid 5-(4-methoxy-benzyl)-4-oxo-4,5,6,7-tetrahydro-pyrazolo[1,5-a]pyrazin-2-ylmethyl ester

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Reaction Steps

Acetyl chloride (0.043 mL, 0.055 mmol) was added to a stirred solution of 5-(4-methoxy-benzyl)-4-oxo-4,5,6,7-tetrahydro-pyrazolo[1,5-a]pyrazine-2-carboxylic acid ethyl ester (3.8 g, 11.5 mmol), TEA (0.1 mL, 0.75 mmol) and DMAP (6.1 mL, 0.05 mmol)) in DCM (2.5 mL) at 0° C. The mixture was stirred at room temperature for 2 hours. Then more acetyl chloride (0.01 mL, 0.01 mmol) was added and the mixture was stirred at room temperature for 2 hours more. The mixture was treated with a saturated solution of Na2CO3 and extracted with DCM. The organic layer was separated, dried (MgSO4), filtered and the solvents evaporated in vacuo to yield acetic acid 5-(4-methoxy-benzyl)-4-oxo-4,5,6,7-tetrahydro-pyrazolo[1,5-a]pyrazin-2-ylmethyl ester (142 mg, 86% yield) as a colourless oil that was used in the next step without further purification.

Provenance & Evidence