Synthesis of indeno[2,1‐a]pyrrolo[3,4‐c]carbazole lactam regioisomers using ethyl cis‐β‐cyanoacrylate as a dienophile and lactam precursor

Reported here is the synthesis and characterization of the indenopyrrolocarbazole ring system utilizing a Diels‐Alder reaction with 2‐indenylindole and maleimide. Clemmensen reduction of imide 10 furnished the 5‐oxo ( 16 ) and 7‐oxo ( 17 ) lactam regioisomers. A new regiospecific route to 5‐oxo 16 was developed using ethyl cis‐β‐cyanoacrylate as the dienophile. The regio and stereochemical characterization of the cycloadducts was confirmed by X‐ray crystallography.