Phosphoric Acid → HCID 12836919, compound

Participants

Reaction Conditions

Reaction Steps

4.4 g of diethyl ethoxymethylenemalonate was added to 3.4 g of 2-methyl-4-chloroindoline and the mixture was heated on an oil bath at 110° to 120° C. for 40 minutes. 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 1 hour. After completion of the reaction, the mixture was allowed to cool to 60° C., poured into ice water and rendered neutral with a 10% aqueous sodium hydroxide solution. The crystals precipitated were collected by filtration and washed with water. The crystals thus treated 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 precipitate crystals. Recrystallization of the product from dimethylformamide gave 3.8 g of 9-chloro-2-methyl-6-oxo-1,2-dihydro-6H-pyrrolo[3,2,1-ij]quinoline-5-carboxylic acid as white needles having a melting point of 288° to 290° C.

Provenance & Evidence