Synthesis of 1-substituted ellipticines by a new route to pyrido[4,3-b]carbazoles

Abstract

A new approach to pyrido[4,3-b]carbazole leading to 1-substituted ellipticines derivatives is described. A five-step synthesis starting from arenediazonium chlorides and 1-morpholinocyclohexenes gave 2-formyl-1-methyl-3,4-dihydrocarbazoles which were then aromatized by manganese dioxide to 2-formyl-1-methylcarbazoles. Knoevenagel malonic acid condensation afforded the corresponding trans-acrylic acids, the azides of which were cyclized in boiling diphenyl ether giving pyrido[4,3-b]carbazol-1 (2H)ones. These compounds were transfomed into 1-chlorojellipticines in boiling phosphorus oxychloride. Finally, the nucleophilic displacement of the chlorine atom by γ-diethylaminopropylamine provided the previously unknown 1-substituted pyrido[4,3-b]carbazoles.