Abstract: The synthesis of 5-unsubstituted pyrido[3,2,1-jk]carbazol-6-one 4 can be achieved by the reaction of carbazole 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 carbazole and malonic acid.
The 5-acetyl-4-hydroxy derivative 3> 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 4-azido-5-nitro-pyrido[3,2,1-jk]carbazol-6-one 21> , which cyclizes on thermolysis to a 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 pyrido[3,2,1-jk]carbazol-6-one 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 with diethyl diethyl malonate 5-nitro-6-oxopyrido[3,2,1-jk]carbazol-4-yl)-malonate 23; with dimethyl malonate, 5-nitro-6-oxopyrido[3,2,1-jk]carbazol-4-yl)-acetate was obtained by loss of carbon dioxide.