Benzenesulfonyl chloride → 1H-Pyrazole-5-carboxylic acid, 1-(3-chloro-2-pyridinyl)-4,5-dihydro-3-[(phenylsulfonyl)oxy]-, ethyl ester

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Reaction Steps

Triethylamine (1.85 g, 18.5 mmol) was added dropwise over 1 h to a mixture of ethyl 2-(3-chloro-2-pyridinyl)-5-oxo-3-pyrazolidinecarboxylate (i.e. the product of Example 1, Step A) (5.0 g, 18.5 mmol) and benzenesulfonyl chloride (3.27 g, 18.5 mmol) in dichloromethane (20 mL) at 0° C. The temperature was not allowed to exceed 1° C. After stirring the reaction mixture for an additional 2 h, a further portion of benzenesulfonyl chloride (0.5 g, 1.85 mmol) was added. Then a further portion of triethylamine (0.187 g, 1.85 mmol) was added dropwise to the mixture. After stirring for 0.5 h more, the mixture was partitioned between water (100 mL) and dichloromethane (100 mL). The organic layer was dried (MgSO4) and evaporated to provide the title product as an orange solid (7.18 g, 94% yield). Product recrystallized from ethyl acetate/hexanes melted at 84-85° C.

Provenance & Evidence