Syntheses and Reactions of 5-Unsubstituted 11b-Methyl-1,2,3,11b-tetrahydro-pyrido[3,2,1-jk]carbazoles Having a Strychnos Alkaloids Partial Structure

a-Methyl-2,3,3,4a-tetrahydro-1 H-carbazoles 3, obtained from arylhydrazines 1 and 2-methylcy- clohexanone 2, react with diethyl malonate 5a by cyclocondensation to 7-hydroxy-13b-methyl- tetrahydro-pyrano(2',3':4,5)pyrido(3,2,1- jk )carbazolediones 6. With methanetricarboxylates 5b,c , cyclocondensation forms a mixture of pyrano-pyrido-carbazole-carboxylates 7 and pyrido-carbazole- carboxylates 8. Degradation of pyrano-pyrido-carbazolediones 6 by alkaline ring-opening and decarboxylation leads to 5-acetyl derivatives 10 . Deacetylation with sulfuric acid reveals the 5-un sub- stituted 4-hydroxy-11b-methyl-1,2,3,11b-tetrahydro- 6 H-pyrido(3,2,1-jk)carbazol-6-one (9). Pyrido- carbazolone 9 was also obtained in a single step reaction from t etrahydrocarbazole 3a and malonic acid 5d with phosphoryl chloride as catalyst in low yields . Electrophilic halogenation of 9 takes place at position 5 and gives 5-bromo compou nd 15 or 5,5-dihalogenated products 14 , 16 or 17 , depending on the reaction conditions. Nitration t akes also place in an electrophilic reaction to give 4-hydrox y-5-nitro-pyrido-carbazolone 20 . Nucleophilic exchange of the 4-hydroxy group in pyridocarbazolones 9 and 20 by reaction with phosphoryl chloride gives reactive 4-chloro intermediates 18 and 21 , which react with sodium azide to 4-azido derivati ves 19 and 22 . 4-Azido-5-nitro-pyrido-carbazolone 22 with the reactive ortho-nitro group in the neighborship of the azido group cyclizes thermolyti cally to furoxane 23 . This reaction was studied by differential scanning calorimetry (DSC).