The reaction of 3-methoxy-2-nitrobenzoic acid methyl ester (I) with 2-pentanone (II) by means of LDA gives 1-(3-methoxy-2-nitrophenyl)hexane-1,3-dione (III), which is condensed with dimethylformamide dimethyl acetal (DMFA) yielding the enamine (IV). The cyclization of (IV) by hydrogenation with H2 over Pd/C affords quinolone (V), which is treated with refluxing POCl3 to give 1-(4-chloro-8-methoxyquinolin-3-yl)-1-butanone (VI). Finally, this compound is condensed with o-toluidine in refluxing dioxane. The intermediate, the quinolone (V) has also been obtained as follows: The reaction of 1-chloro-1-hexen-3-one (VIII) with NaOH in methanol gives 3-oxohexanal (IX) (enol form), which is condensed with 2-amino-3-methoxybenzoic acid methyl ester (X) yielding the enamine (XI). Finally, this compound is cyclized by means of sodium methoxide to afford the desired quinolone (V).

The condensation of 8-methoxyquinolin-4(1H)-one (XII) with o-toluidine (VII) gives the secondary amine (XIII), which is brominated with NBS to the 3-bromo derivative (XIV). Finally, this compound is condensed with N-methoxy-N-methylbutyramide (XV) by means of BuLi to afford the target compound.

The condensation of ethoxymethylenemalonic acid diethyl ester (XVI) with 2-methoxyaniline (XVII) in hot toluene gives the aminomethylene derivative (XVIII), which is cyclized with POCl3 and polyphosphoric acid (PPA) at 100 C yielding 8-methoxy-4-oxo-1,4-dihydroquinoline-3-carboxylic acid ethyl ester (XIX), which is hydrolyzed with NaOH in methanol to the corresponding free acid (XX), and treated with refluxing SOCl2 to afford 4-chloro-8-methoxyquinoline-3-carbonyl chloride (XXI). The reaction of (XXI) with dimethylamine gives the corresponding amide (XXII), which is condensed with o-toluidine (VII) in refluxing dioxane yielding the expected secondary amine (XXIII). Finally, this compound is treated with propylmagnesium chloride (XXIV) to afford the target compound.

The reaction of acyl chloride (XXI) with propylmagnesium chloride (XXIV) gives 1-(4-chloro-8-methoxyquinolin-3-yl)-1-butanone (XXV), which is finally condensed with o-toluidine (VII) in refluxing dioxane to afford the target compound.

The cyclization of (XVIII) in refluxing POCl3 gives 4-chloro-8-methoxyquinoline-3-carboxylic acid ethyl ester (XXVI), which is condensed with o-toluidine (VII) in refluxing dioxane yielding the secondary amine (XXVII). Finally, this compound is condensed with propylmagnesium chloride (XXIV) to afford the target compound.

This compound has been obtained by several related ways: 1) The reaction of ethyl butyrylacetate (I) with triethyl orthoformate and Ac2O gives acrylate (II), which by reaction with o-toluidine (III) yields the aminoacrylate (IV). The cyclization of (IV) by heating at 255 C in diphenyl ether affords the quinolone (V), which is treated with refluxing POCl3 to give 1-(4-chloro-8-methoxyquinolin-3-yl)-1-butanone (VI). The demethylation of (VI) with AlCl3 or BBr3 yields the 8-hydroxyquinoline (VII), which is condensed with o-toluidine (VIII) in refluxing dioxane affording 1-[8-hydroxy-4-(2-methylphenylamino)quinolin-3-yl-1-butanone (IX). Finally, this compound is condensed with 2-bromomethanol (X) by means of potassium tert-butoxide or with ethylene carbonate (XI) by means of K2CO3. 2) The condensation of chloroquinoline (VI) with o-toluidine (VIII) in refluxing dioxane gives 1-[8-methoxy-4-(2-methylphenylamino)quinolin-3-yl-1-butanone (XII), which is demethylated with AlCl3 or BBr3 as before yielding the previously reported 1-[8-hydroxy-4-(2-methylphenylamino)quinolin-3-yl-1-butanone (IX).

The intermediate quinolone (V) has also been obtained by two other ways: a) The reaction of 3-methoxy-2-nitrobenzoic acid methyl ester (XIII) with 2-pentanone (XIV) by means of LDA gives 1-(3-methoxy-2-nitrophenyl)hexane-1,3-dione (XV), which is condensed with dimethylformamide dimethyl acetal (DMFA) yielding the enamine (XVI). Finally, this compound is cyclized by hydrogenation with H2 over Pd/C to afford the desired quinolone (V). b) The reaction of 1-chloro-1-hexen-3-one (XVII) with NaOH in methanol gives 3-oxohexanal (XVIII) (enol form), which is condensed with 2-amino-3-methoxybenzoic acid methyl ester (XIX) yielding the enamine (XX). Finally, this compound is cyclized by means of sodium methoxide to afford the desired quinolone (V).

The condensation of 8-methoxyquinolin-4(1H)-one (XXI) with o-toluidine (VIII) gives the secondary amine (XXII), which is brominated with NBS to the 3-bromo derivative (XXIII). Finally, this compound is condensed with N-methoxy-N-methylbutyramide (XXIV) by means of BuLi to afford intermediate (XII).

The condensation of ethoxymethylenemalonic acid diethyl ester (XXV) with 2-methoxyaniline (XXVI) in hot toluene gives the aminomethylene derivative (XXVII), which is cyclized with POCl3 and polyphosphoric acid (PPA) at 100 C yielding 8-methoxy-4-oxo-1,4-dihydroquinoline-3-carboxylic acid ethyl ester (XXVIII), which is hydrolyzed with NaOH in methanol to the corresponding free acid (XXIX), and treated with refluxing SOCl2 to afford 4-chloro-8-methoxyquinoline-3-carbonyl chloride (XXX). The reaction of (XXX) with dimethylamine gives the corresponding amide (XXXI), which is condensed with o-toluidine (VIII) in refluxing dioxane yielding the expected secondary amine (XXXII). Finally, this compound is treated with propylmagnesium chloride (XXXIII) to afford the intermediate (XII).

The reaction of acyl chloride (XXX) with propylmagnesium chloride (XXXIII) gives 1-(4-chloro-8-methoxyquinolin-3-yl)-1-butanone (XXXIV), which is finally condensed with o-toluidine (VIII) in refluxing dioxane to afford the intermediate (XII).

The cyclization of (XXVII) in refluxing POCl3 gives 4-chloro-8-methoxyquinoline-3-carboxylic acid ethyl ester (XXXV), which is condensed with o-toluidine (VIII) in refluxing dioxane yielding the secondary amine (XXXVI). Finally, this compound is condensed with propylmagnesium chloride (XXXIII) to afford the intermediate (XII).