Sodium Bicarbonate → Methyl 2-(3-Chloro-2-pyridyl)-5-oxopyrazolidine-3-carboxylate

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Reaction Steps

The crude product of Step B (i.e. methyl 2-bromo-4-chloro-4-oxobutanoate) (11.00 g, ˜47.4 mmol) in acetonitrile (25 mL) was added over 65 minutes to a mixture of 3-chloro-2(1H)-pyridinone hydrazone (alternatively named (3-chloro-pyridin-2-yl)-hydrazine) (6.55 g, 45.6 mmol) and sodium bicarbonate (9.23 g, 0.110 mol) in acetonitrile (60 mL) at 0° C. The mixture was then allowed to warm to room temperature and was stirred for 3 h. The mixture was then warmed and maintained at 38° C. for 8 h. Then the mixture was allowed to cool, and the solvent was removed by evaporation under reduced pressure. Water (25 mL) was added, and acetic acid (about 1.9 mL) was added until the slurry had a pH of about 5. After 2 h, the product was isolated by filtration, rinsed with water (10 mL) and dried in vacuo to provide the title compound as a pale yellow solid (11 g, 89.8% yield). A sample recrystallized from ethanol melted at 147-148° C.

Provenance & Evidence