Hydrochloric Acid → 1-Phenyl-1,4-dihydrothiochromeno(4,3-c)pyrazole-3-carboxylic acid

Participants

Reaction Steps

1,4-Dihydro-1-phenyl-[1]-benzothiopyrano[4,3-c]pyrazole-3-carboxylic acid, ethyl ester (3.36 g) suspended in dioxane (60 ml) is treated with N/1 NaOH (30 ml) under stirring at room temperature for 5 hours. The reaction mixture is diluted with ice water and acidified to pH 3 with 37% HCl. The precipitate is filtered, washed with water and dried in vacuo at 50° C. to give 1,4-dihydro-1-phenyl-[1]-benzothiopyrano[4,3-c]pyrazole-3-carboxylic acid (2.8 g) which is reacted with oxalyl chloride (17 g) under stirring, at room temperature for 8 hours. The reaction mixture is evaporated to dryness in vacuo and the residue, 1,4-dihydro-1-phenyl-[1]-benzothiopyrano[4,3-c]pyrazole-3-carbonyl chloride (2.9 g), is dissolved in dimethylformamide (10 ml) and added under stirring to a suspension obtained by treatment of 2-cyano-acetylamino-pyridine (1.62 ) with 50% sodium hydride (0.5 g) in dimethylformamide (5 ml). The reaction mixture is kept at room temperature for 20 hours. The basic aqueous solution is washed with ethyl ether and then is acidified to pH 5 with 37% HCl. The precipitate is filtered, washed with water and then crystallized from ethanol to give 2.7 g of 2-cyano-3-(1,4-dihydro-1-phenyl-[1]-benzothiopyrano[4,3-c]pyrazol-3-yl)-3-oxo-N-(2-pyridyl)-propanamide, m.p. 258°-260° C.

Provenance & Evidence