Diethyl (ethoxymethylene)malonate → 7-Chloro-1-ethyl-1,4-dihydro-8-methyl-4-oxo-3-quinolinecarboxylic acid

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Reaction Conditions

Reaction Steps

Ten grams of N-ethyl-2-methyl-3-chloroaniline is allowed to react with 15 g of diethyl ethoxymethylenemalonate under heating at 110° C. for 30 minutes. Then, polyphosphoric acid (obtained from 50 g each of phosphoric acid and phosphorus pentaoxide) is added to be subjected to the reaction at 140° C. for 40 minutes. After the reaction, the mixture is poured into 600 g of water and ice, resulting in crystals separated out. The crystals are recovered by filtration, and a 10% sodium hydroxide solution is added to the fitrate and the mixture is refluxed for 1 hour. After refluxing, the mixture is treated with activated carbon and adjusted to pH 2 with concentrated hydrochloric acid, whereby there separate out light yellow crystals. Recrystallization from dimethylformamide yields 11 g of 1-ethyl-7-chloro-8-methyl-4-oxo-1,4-dihydroquinoline-3-carboxylic acid as the white, needle-like crystals. mp. 221°-222° C.

Provenance & Evidence