The synthesis and stereochemistry of some pyrido[3,4-d]carbazole derivatives

Pyrido3,4-d]carbazole derivatives have been synthesised from N-acetyl-5-oxodecahydro-isoquinoline by the Fischer indole synthesis, and their stereochemistry established by ¹H-NMR spectroscopy. In contrast to experience with simpler systems, cyclisation in acetic acid gave only the alternative pyrido3,4-a]-carbazole, and the desired pyrido3,4-d]carbazole formation occurred only in the presence of sodium acetate.