Diethyl (ethoxymethylene)malonate → 1,3-Diethyl 2-[[(3-nitrophenyl)amino]methylene]propanedioate

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Reaction Steps

The intermediate lower-alkyl 7-amino-1-R-1,4-dihydro-4-oxo-3-quinolinecarboxylates of formula II are prepared in several steps by convention procedures as follows: m-nitroaniline is reacted with diethyl ethoxymethylenemalonate to form diethyl m-nitroanilinomethylenemalonate which is cyclized by heating in an appropriate solvent such as Dowtherm® A (eutectic mixture of 26.5% diphenyl and 73.5% diphenyl ether) or mineral oil at about 250°-260° C. to produce lower-alkyl 1,4-dihydro-7-nitro-4-oxo-3-quinolinecarboxylate, which is then alkylated at the 1-position by reaction with an appropriate alkylating agent, e.g., methyl, ethyl or n-propyl halide, diethyl sulfate, triethyl phosphate, or the like, preferably in the presence of an inert solvent, e.g., dimethylformamide, and an appropriate acid-acceptor, e.g., anhydrous potassium carbonate, to produce lower-alkyl 1-R-1,4-dihydro-7-nitro-4-oxo-3-quinolinecarboxylate, catalytically hydrogenating the 7-nitro compound in the presence of an appropriate catalyst, e.g., palladium-on-charcoal, to produce the corresponding ethyl 7-amino-1-R-1,4-dihydro-4-oxo-3-quinolinecarboxylate (II).

Provenance & Evidence