Unstable 8-p-tolylsulfonylimino-5,8-dihydroquinolin-5-one was generated by oxidation of the corresponding reduced form in acetic acid; it reacted in situ with hydrogen chloride and sodium p-toluenesulfinate to give the corresponding 6-substituted 5-hydroxy-8-aminoquinolines.There are almost no published data on N-substituted 8-imino-5,8-dihydroquinolin-5-ones. An attempt was made to correlate antimalarial activity of 8-amino-6-methoxyquinolines with their ability to undergo oxidation to 8-imino-6-methoxy-5,8-dihydroquinolin-8-ones [1], though the corresponding quinoid metabolites were not isolated by independent synthesis [2] because of their instability. The only stable compound of this series, 6-(4-methoxyphenylamino)-8-(4-methoxyphenylimino)-5,8-dihydroquinolin-5-one was obtained by treatment of 6-piperidino-5,8-dihydroquinoline-5,8-dione with excess p-methoxyaniline in acetic acid [3].In the preceding communications we reported on the reactivity of 8-p-tolylsulfonylimino-5,8-dihydroquinolin-5-one derivatives. We found that reactions of these compounds with nucleophilic reagents are governed by the tosylimino group rather than by the endocyclic nitrogen atom [4,5]. In the present work we made an attempt to synthesize 8-arylsulfonylimino-5,8-dihydroquinolin-5-ones. The initial model compound, 8-p-tolylsulfonylimino-5,8-dihydroquinolin-5-one (I), and its derivatives were synthesized following the reaction sequence shown in Scheme 1. The reaction of 8-nitroquinoline (II) with hydroxylamine hydrochloride in alcoholic alkali afforded 5-amino-8-nitroquinoline (III). The latter was converted into 5-hydroxy-8-nitroquinoline (IV) by alkaline hydrolysis according to a specially developed procedure. For this purpose, nitro compound IV was reduced to 8-amino-5-hydroxyquinoline dihydrochloride (V) with tin(II) chloride in hydrochloric acid. Compound V was treated with p-toluenesulfonyl chloride in methanol in the presence of 2 equiv of pyridine to obtain 8-p-tolylsulfonylamino-5-hydroxyquinoline hydrochloride (VI). Oxidation of tosyl derivative VI with (diacetoxy-l 3 -iodanyl)benzene in acetic acid in the presence of an equimolar amount of sodium acetate afforded quinone imine I as a dark green solid material which gradually dissolved in the reaction mixture, giving rise to a dark blue solution. We failed to isolate quinone imine I as individual substance. Nevertheless, by treatment of the reaction mixture at the moment of formation of quinone imine I precipitate with hydrochloric acid or sodium p-toluenesulfinate dihydrate we succeeded in isolating new compounds, 6-chloro-5-hydroxy-8-p-tolylsulfonylaminoquinoline hydrochloride (VII) and 5-hydroxy-6-p-tolylsulfonyl-8-p-tolylsulfonylaminoquinoline (VIII), respectively.The presence of a substituent in position 6 of the quinoline ring system was proved as follows. The oxidation of salt VII with (diacetoxy-l 3 -iodanyl)benzene under the same conditions as in the generation of quinone imine I gave unstable 6-chloro-8-p-tolylsulfonylimino-5,8-dihydroquinolin-5-one (IX) w...
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Quinoline derivatives R 0410Quinone Imines with a Fused Azine Ring. Part 3. Synthesis and Reactivity of 8-p-Tolylsulfonylimino-5,8-dihydroquinolin-5-one Derivatives. -The title 8-tolylsulfonylimino-5,8-dihydroquinolin-5-one (VII) is generated by oxidation of corresponding, readily available aminoquinolinol (VI). In situ reaction of this unstable quinone imine with hydrogen chloride or sodium p-toluenesulfinate provides access to the new aminoquinolinol derivatives (VIII) and (X), respectively. -(BELOV, A. V.; NICHVOLODA, V. M.; Russ.
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