Halogenation of the aluminum chloride complexes of isoquinoline or quinoline gave in good yield halogen derivatives substituted in the benzenoid ring. Bromination of the aluminum chloride-isoquinoline complex gave the following sequence in substitution: 5-bromo-, 5,8-dibromo-, 5,7,8-tribromo-. To obtain good yields of 5,7,8-tribromoisoqumoline, it was necessary to brominate 5,8-dibromoisoquinoline, not isoquinoline itself. Bromination of the aluminum chloride complex of quinoline gave similar results except that 5,6,8-tribromoquinoline was obtained by bromination of 5,8-dibromoquinoline. Chlorination of the aluminum chloride complexes of both quinoline and isoquinoline gave results very similar to bromination. 5,6,7,6,7,8-tetrachloroquinoline were isolated also. Identification of many of these compounds was carried out by synthesis from known compounds as shown in the Scheme I.
Interest in the biological activity of certain halogenated derivatives of quinoline and isoquinoline prompted t h e preparation of other derivatives similar to those previously reported (1). In order to obtain halogenated quinoline moieties which had different water-oil solubility ratios, the compounds described in the experimental section were synthesized.
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