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51. Nucleophilic chlorination of 3-formyl-4-hydroxy-quinolin-2(1H)-ones
Fiala W., Stadlbauer W., Journal f. Prakt. Chem. 335 (1993), 128-134

Abstract: Chlorination of 1-substituted 3-formyl-4-hydroxy-2-quinolones with phosphorylchloride leads to 4-chloro-3-dichloromethylquinolones, which can be hydrolyzed to 4-chloro-3-formylquinolones. Using the anilinomethylene quinolinediones, at low temperatures the formylquinolones can be obtained directly, whereas at high temperatures cleavage of the tautomeric azomethine moiety followed by subsequent ring closure to the naphthyridines takes place. With 1-unsubstituted 3-formyl-4-hydroxy- 2-quinolones either the 3-dichloromethylquinolone or the 2,4-dichloro-3- dichloromethylquinoline is obtained depending on the reaction conditions. Similar results are obtained with the 1-unsubstituted anilinomethylene compounds. Attempts to obtain the 3-formyl-2,4-dichloroquinoline were unsuccessful because in all experiments the 2-chloro group was converted to an oxygen function.

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