Synthesis of regioisomeric difluoro- and 8-chloro-9- fluorobenz [g] isoquinoline-5,10-diones and SNAr displacements studies by diamines: bis(aminoalkyl)aminobenz[g] isoquinoline-5,10-diones

Abstract Convenient pathways have been developed for the synthesis of 6,7−, 6,8-, 7,9- and 8,9-difluorobenz[ g ] isoquinoline-5,10-diones and 8-chloro-9-fluorobenz [ g ] isoquinoline-5,10-dione. The crucial step in these synthesis involved the Ni-catalyzed coupling of the difluoro- or chlorofluorobenzylic zinc bromides with ethyl 3-chloroisonicotinate or ethyl 4-chloronicotinate. The reactions of the 6,7- or 8,9-difluoro regioisomers with N,N -dimethylethylenediamine led to quaternary salts which were formed by intramolecular displacements from the initial mono displacement products. These cyclizations could be obviated with the use of 3-dimethylaminopropylamine in the displacements which led to the desired bis (aminoalkyl) amino substitution products. Treatment of 8-chloro-9-fluorobenz [ g ] isoquinoline-5,10-dione with N,N -dimethylethylenediamine led to the regioselective displacement of fluoride. Treatment of this mono substitution product with excess N,N -dimethylethylenediamine led only to the intramolecular cyclization product which was also obtained by reaction of 8,9-difluorobenz[ g ] isoquinoline-9,10-dione with N,N -dimethylethylenediamine. The 6,8- and 7,9-difluoro analogues on treatment with N,N -dimethylethylenediamine or 3-dimethylaminopropylamine led to the expected bis substitution products.