Process for the preparation of 4-hydroxy-quinoline-3-carboxylic acids

A process for the preparation of a compound of the formula in which Y is a nitrile group, an ester group COOR1 or an acid amide CONR2R3, R1, R2 and R3 each independently is hydrogen or C1-C4-alkyl, and R3 may also be phenyl, and X2, X3, X4 and X5 each independently is hydrogen, halogen, nitro, cyano, alkyl having 1-3 carbon atoms, alkoxy having 1-3 carbon atoms, alkylmercapto having 1-3 carbon atoms, alkyl-sulphonyl having 1-3 carbon atoms, or a phenylsulphonyl group which is optionally substituted in the aryl radical, comprising reacting an aminoacrylate of the formula in which X1 is halogen, a nitro group, an alkoxy, alkoxy, alkylmercapto or alkylsulphonyl group having 1-3 carbon atoms in each case, or an arylsulphonyl group, W is hydrogen or a -CH2CH2Z radical, Z is a nitrile group, an ester group COOR4 or an acid amide group CONR5R6, and R4, R5 and R6 each independently is hydrogen or C1-C4-alkyl, and R5 may also be phenyl, with an acid acceptor in an aprotic solvent. Some of the reactants are new, as are the products which are intermediates for antibacterially active 1-alkyl-4-quinolone-3-carboxylic acids.