Methanol → 4-chloro-1-(difluoromethyl)-1H-pyrazole-3-carboxylic acid

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Reaction Steps

A solution of 4-chloro-1-difluoromethyl-1H-pyrazole-3-carboxylic acid methyl ester (540 mg, 2.6 mmol) in tetrahydrofuran (18 ml) was treated at room temperature with a solution of lithium hydroxide (135 mg, 5.6 mmol) in a 1:1-mixture of water and methanol (12 ml). After 1 hour the reaction was complete, and the solvents were evaporated at reduced pressure. The residue was dissolved in water (10 ml) and acidified with hydrochloric acid (2M). Extraction with ethyl acetate, drying of the organic layer over sodium sulphate, and evaporation at reduced pressure yielded a white solid (555 mg) which was triturated with pentane (10 ml). The solid material was filtered, washed with pentane and dried. After drying at reduced pressure the 4-chloro-1-difluoromethyl-1H-pyrazole-3-carboxylic acid was obtained as a white solid (477 mg, 95%); (calculated) C5H3ClF2N2O2 [196.540]; (found) [M'H]−=195.

Provenance & Evidence