CS235166B1 - 3-Anilino-1,5-dimethyl-4-pyrazolecarboxylic acid and its esters and processes for their preparation - Google Patents

Abstract

The invention relates to 3-anilino-1,5-dimethyl-4-pyrazolecarboxylic acid and its esters of the general formula I where R denotes a hydrogen atom or an alkyl group with 1 to 3 carbon atoms, preferably an ethyl group. These new, previously undescribed substances serve as intermediates for the synthesis of compounds with antiviral activity.

Description

The present invention relates to 3-anilino-1,5-dimethyl-4-pyrazolecarboxylic acid and its esters of formula I

O- _HN W _{CH 3} (I) wherein R represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, preferably an ethyl group.

These compounds are novel and serve as intermediates for the preparation of biologically important preparations, in particular with antiviral activity (cf. No. 255 168).

The compounds were prepared by the process of the invention, which first comprises alkylating the sodium salt of 3-anilino-4-alkoxycarbonyl-5-methylpyrazole, wherein the alkoxy group contains 1 to 3 carbon atoms with methyl iodide in dimethylformamide at 0 ° C to 30 ° C. ° C, preferably at 20 ° C, to give the corresponding 3-anilino-1,5-dimethyl-4-pyrazolecarboxylic acid alkyl ester. The resulting ester is saponified by boiling with aqueous ethanolic sodium hydroxide solution to give 3-anilino-1,5-dimethyl-4-pyrazolecarboxylic acid.

The following examples illustrate the invention but do not limit it in any way.

Example 1

3-Anilino-1,5-dimethyl-4-pyrazolecarboxylic acid ethyl ester

To a solution of 18.5 g of 3-anilino-4-ethoxycarbonyl-5-methylpyrazole (75 mmol) in 100 ml of dimethylformamide was added under stirring under nitrogen 2.5 g of 80% sodium hydride and the mixture was stirred at 20 ° C for 1 hour. . After dropwise addition of 11.8 g of methyl iodide (83 mmol), the mixture was stirred for an additional 2 hours. After filtering off the insoluble matter, the filtrate was evaporated to dryness. Crystallization of the residue from ethanol gave 16.7 g (85.8%), mp 90.6-91.0 ° C.

Example 1 a d 2

3-Anilino-1,5-dimethyl-4-pyrazolecarboxylic acid

To a solution of 13 g of 3-anilino-1,5-dimethylpyrazolecarboxylic acid ethyl ester (50 mmol) in 200 ml of ethanol at 50 ° C was added a solution of 20 g of sodium hydroxide in 250 ml of water. The mixture was refluxed for 2 hours, after cooling, the solution was acidified to pH 4 with concentrated hydrochloric acid and the precipitate was filtered off with suction and washed with water. 10.2 g (88.2%) of m.p. 184.5-185.7 ° C were obtained.

Claims (3)

1. 3-Anilino-1,5-dimethyl-4-pyrazolecarboxylic acid and its esters of the general formula I ROOC ~ p = q -CH ₃ Η N (i where R is hydrogen or C 1 -C 3 alkyl, preferably ethyl). 2. A process for the preparation of 3-anilino-1,5-dimethyl-4-pyrazolecarboxylic acid, characterized in that the 3-anilino-1,5-alkyl alkyl ester of the invention is dimethyl-4-pyrazolecarboxylic acid wherein alkyl is methyl, ethyl or propyl, preferably ethyl, is saponified by boiling with aqueous ethanolic sodium hydroxide solution. 3. A process for the preparation of a compound according to claim 1, wherein R is C1 -C3 alkyl, preferably ethyl, characterized in that the sodium salt of 3-anilino-4-alkoxycarbonyl-5-methylpyrazole, wherein the alkoxy group contains 1; to 3 carbon atoms, preferably 3-anilino-4-ethoxycarbonyl-5-methylpyrazole was alkylated with methyl iodide in DMF at 0 ° C to 30 ° _C, advantageously at 20 ° C.