Hydrochloric Acid → 8,9-dichloro-5-methyl-6,7-dihydro-1-oxo-1H,5H-benzo[ij]quinolizine-2-carboxylic acid

Participants

Reaction Conditions

Reaction Steps

A mixture of 3.2 g of 5,6-dichloro-1,2,3,4-tetrahydroquinaldine and 3.2 g of diethyl ethoxymethylenemalonate was allowed to react by heating at 160° C. for 30 minutes. Then 13 g of polyphosphoric acid prepared from 6.5 g of phosphorus pentoxide and 6.5 g of phosphoric acid was added to the mixture and the resulting mixture was allowed to react by heating at 140° to 150° C. for 1 hour. After completion of the reaction, the mixture was poured onto 100 g of ice, followed by rendering the mixture to pH 4 to 5 with a 40% aqueous sodium hydroxide solution to precipitate crystals. The crystals were collected by filtration, dried and mixed with 50 ml of a 10% aqueous sodium hydroxide solution. The mixture was allowed to react at 100° to 110° C. for 1 hour. After cooling, the reaction mixture was rendered acidic with concentrated hydrochloric acid to precipitate crystals. Recrystallization of the crystals thus-obtained from ethanol gave 2.3 g of 8,9-dichloro-5-methyl-6,7-dihydro-1-oxo-1H,5H-benzo[ij]quinolizine-2-carboxylic acid having a melting point of 269° to 271° C.

Provenance & Evidence