反应详情

To a solution of 5-cyclopropyl-2H-pyrazole-3-carboxylic acid ethyl ester (202 mg) in N,N-dimethylformamide (4 ml) was added at 0° C. N-chlorosuccinimide (199 mg) and stirring was continued at 22° C. for 15 hours. For the workup, The mixture was partitioned between water and ethyl acetate, the organic layer was dried, evaporated and the residue purified by chromatography on silica using a 8:1-mixture of n-heptane and ethyl acetate as the eluent to give 4-chloro-5-cyclopropyl-2H-pyrazole-3-carboxylic acid ethyl ester (215 mg) as a pale yellow liquid. MS (ISP): m/z=215.2 [M+H]+. b) To a solution of 4-chloro-5-cyclopropyl-2H-pyrazole-3-carboxylic acid ethyl ester (210 mg) in dioxane (4 ml) was added at 22° C. a solution of sodium hydroxide (3.0 M, 0.65 ml), and stirring was continued at 22° C. for 15 hours and at 60° C. for 3 hours. For the workup, the mixture was partitioned between aqueous hydrochloric acid (1.0 M) and ethyl acetate, the organic layer was dried and evaporated to give the title compound (161 mg) as a pale yellow solid. MS (ISP): m/z=184.8 [M−H]−.

1. customFor the workup, The mixture was partitioned between water and ethyl acetate
2. customthe organic layer was dried
3. customevaporated
4. customthe residue purified by chromatography on silica using a 8