Phosphoric Acid → HCID 12836918, compound

Participants

Reaction Conditions

Reaction Steps

4.4 g of diethyl ethoxymethylenemalonate was added to 3 g of 4-chloroindoline and the mixture was heated on an oil bath at 110° to 120° C. during which time liberation of ethanol was observed. 20 g of polyphosphoric acid prepared from 10 g of phosphoric acid and 10 g of phosphorus pentoxide was added thereto and the mixture was heated on an oil bath at 130° to 140° C. for 40 minutes. After completion of the reaction, the mixture was allowed to cool to 60° C., poured into water and rendered neutral with a 10% aqueous sodium hydroxide solution. The crystals precipitated were collected by filtration and washed with water. The crystals thustreated were mixed with 50 ml of a 10% aqueous sodium hydroxide solution and the mixture was heat-refluxed on an oil bath for 1 hour. As the reaction proceeded the mixture changed to a uniform solution. The solution was treated with activated carbon while hot followed by filtration. The filtrate was rendered acidic with concentrated hydrochloric acid to obtain 3.5 g of 9-chloro-6-oxo-1,2-dihydro-6H-pyrrolo[3,2,1-ij]quinoline-5-carboxylic acid. Recrystallization of the product from dimethylformamide gave 3.5 g of white needles having a melting point of 307.5° C. (decomposition).

Provenance & Evidence