The synthesis of 5-unsubstituted pyrido[3,2,1-jk]carbazol-6-one 4 can be achieved by the reaction of carbazole (1) and malonate derivatives, either in a 3-step synthesis via 5-acetyl-pyrido[3,2,1-jk]carbazolone 3 or in a 1-step reaction from 1 and malonic acid.
5-Acetyl derivative can be transformed to 4-azido-pyrido[3,2,1-jk]carbazolone 11, which cyclizes by thermal decomposition to isoxazolo-pyrido[3,2,1-jk]carbazolone 12. The thermolysis conditions were investigated by differential scanning calorimetry (DSC). Nitration of pyrido[3,2,1-jk]carbazol-6-one 4 and subsequent introduction of azide leads to azido derivative 21, which cyclizes on thermolysis to furazan-oxide derivative 22. Again the thermolysis conditions were investigated by DSC.
5-Chloro-5-nitro-pyrido[3,2,1-jk]carbazole-4,6-dione, obtained from 4 by subsequent nitration and chlorination, forms on oxidative thermolysis reaction pyrido[3,2,1-jk]carbazole-4,5,6-trione 17, which reacts e.g. with phenole by acylation to give 5-hydroxy-5-(p-hydroxyphenyl)-pyrido[3,2,1-jk]carbazole-4,6-dione 19. A further C-C-coupling at position 4 starts from 4-chloro-5-nitro-pyrido[3,2,1-jk]carbazol-6-one, which gives e.g. with diethyl malonate 5-nitro-6-oxopyrido[3,2,1-jk]carbazol-4-yl)-malonate 23.
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