Decarbonylative and Dehydrogenative Cascade Annulation of N‐(o‐Cyanobiaryl)acrylamides with Aldehydes.

Decarbonylative and dehydrogenative cascade annulation of aldehydes with N‐(o‐cyanobiaryl)acrylamides was developed for the synthesis of a broad spectrum of alkyl‐ and carbonyl‐substituted pyrido[4,3,2‐gh]phenanthridines. Secondary and tertiary aldehydes can undergo the decarbonylative cascade under DTBP/malonic acid conditions, while aryl, primary, and secondary aldehydes can undergo dehydrogenative reaction under TBHP system. Such transformations were triggered by alkyl and acyl radicals, and the annulations were accomplished through intramolecular additions of carbon‐centered radical to nitrile group and iminyl radical to aromatic ring. [ABSTRACT FROM AUTHOR]