O ácido dimetiléster 1-metilcarbazol-2,3-dicarboxílico, um intermediário chave na síntese de carbazóis b-fusionados, foi transformado com êxito nos seus 6-bromo e 6-nitro derivados via uma substituição eletrofílica numa solução de ácido acético, usando como reagentes N-bromosuccinimida ou nitrato de uréia, respectivamente. Com a N-clorosuccinimida foi também obtido o derivado 6,8-dicloro congênere, em quantidade apreciável. Os carbazodiésteres 6-substituídos foram usados como matéria-prima para

more »

... a preparação de vários novos derivados piridazino-ou pirrolocarbazóis fusionados com cadeias laterais básicas, levando à estrutura básica de compostos antitumorais previamente desenvolvidos. 1-Methylcarbazole-2,3-dicarboxylic acid dimethyl ester, a key intermediate in the synthesis of b-fused carbazoles, was successfully transformed into its 6-bromo and 6-nitro derivative via electrophilic substitution in acetic acid solution, using N-bromosuccinimide or urea nitrate, respectively, as reagents. With N-chlorosuccinimide, a 6,8-dichloro congener was also obtained in substantial amounts. The 6-substituted carbazolediesters were used as building blocks for the preparation of several new pyridazine-or pyrrole-fused carbazoles with basic side chains, featuring the core structure of previously developed antitumor compounds. Electrophilic Substitution of Dimethyl 1-Methylcarbazole-2,3-dicarboxylate J. Braz. Chem. Soc. 1966 Scheme 1. Synthesis of bromo and chloro derivatives of the ester 1. Scheme 2. Nitration of the ester 1 with urea nitrate. Scheme 3. Cyclization of the diesters 2, 3 and 5 into pyridazino[4,5-b]carbazoles. Electrophilic Substitution of Dimethyl 1-Methylcarbazole-2,3-dicarboxylate J. Braz. Chem. Soc. 1968 Scheme 4. Introduction of basic side chains into the pyridazino[4,5-b]carbazole skeleton.