An efficient synthesis of (&plusmn;) 4-hydroxy-9-methoxy-5,11-dimethyl-6<em>H</em>-1,2,3,4-tetrahydro-benzo[<em>b</em>]carbazole

1532-1540In this study, new tetracyclic compounds similar to benzo[b]carbazole have been synthesized. Their structures have been characterized by IR, 1H and 13C NMR, mass spectral and CHN analysis, and correspond to 4-hydroxy-9-methoxy-5,11-dimethyl-6H-1,2,3,4-tetrahydro-benzo[b]carbazole and 9-methoxy-5,11-dimethyl-6H-1,2,3,4-tetrahydro-benzo[b]carbazole. The condensation of 6-methoxy-1,4-dimethyl-9H-carbazole with ethyl 4-chloro-4-oxo-butanoate gives ethyl 4-(6-methoxy-1,4-dimethyl-9H-carbazol-3-yl)-4-oxobutanoate when using tin tetrachloride as catalyst. After reduction of the carbonyl function, the ethyl 4-(6-methoxy-1,4-dimethyl-9H-carbazole-3-yl)butanoate has been obtained. After the saponification reaction, intramolecular cyclisation of the acid form in presence of trifluoroacetic anhydride is followed by reduction of the ketone group by sodium borohydride which leads to the formation of the hydroxylated compound. Therefore, 9-methoxy-5,11-dimethyl-6H-1,2,3,4-tetrahydro-benzo[b]carbazole is obtained in the intramolecular cyclization reaction of 1,4-dimethyl-6-methoxy-3-(4-oxobutyl)-9H-carbazole