Halogenation of Quinolones

A popular method to prepare haloquinolines is the halogenation of quinolones using oxyphosphorus halides, most notably POCI3. The 

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A popular method to prepare haloquinolines is the halogenation of quinolones using oxyphosphorus halides, most notably POCI3. The carbonyl can be located either at the C(2) or the C(4) positions. As depicted in Scheme 1, the C(2) position of quinolone 4 was chlorinated with POCI3 to give 6-bromo-2-chloroquinoline (5) [1]. The subsequent S Ar displacement of the chlorine substituent on 5 with sodium methoxide led to 6-bromo-2-methoxyquinoline. Analogously, chlorination at the C(4) position of quinolones is exemplified by transformations 6 7 [2] and 8 9 [3]. 

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