Hydrochloric Acid → 1,4-Dihydro-1-phenyl-indeno [1,2-c]pyrazole-3-carboxylic acid

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Reaction Steps

1,4-Dihydro-1-phenyl-indeno[1,2-c]pyrazole-3-carboxylic acid, ethyl ester (3 g), prepared according to Example 1, is heated with 1% KOH solution in ethanol (100 ml) at reflux temperature for 20 minutes. The reaction mixture is diluted with ice water and acidified to pH 3 with 37% HCl. The precipitate is filtered, washed with water until neutral and dried in vacuo to give 1,4-dihydro-1-phenyl-indeno [1,2-c]pyrazole-3-carboxylic acid (2.5 g) which is reacted with thionyl chloride (1.2 ml) in dioxane (60 ml) at the reflux temperature for 2 hours. After cooling the reaction mixture is evaporated to dryness in vacuo to give 1,4-dihydro-1-phenyl-indeno[1,2-c]pyrazole-3-carbonyl chloride as crystalline residue. The crude product is dissolved in anhydrous dioxane (30 ml) and reacted for 2 hours under stirring at room temperature with the carbanion obtained by treatment of 2-cyano-acetanilide (1.6 g) with 50% sodium hydride (0.5 g) in anhydrous dimethylformamide/dioxane (1:1 (10 ml) at room temperature. The reaction mixture is then diluted with ice water and acidified to pH 2 with HCl. The precipitate is filtered and washed with water until neutral. Crystallization from dichloromethane/methanol gives 1.6 g of 2-cyano-3-(1,4-dihydro-1-phenyl-indeno [1,2-c]pyrazol-3-yl)-3-oxo-N-phenyl-propanamide, m.p. 273°-277° C.

Provenance & Evidence