Cyano Group Removal from Cyano-Promoted Aza-Diels–Alder Adducts: Synthesis and Structure–Activity Relationship of Phenanthroindolizidines and Phenanthroquinolizidines
Phenanthroindolizidines and phenanthroquinolizidines were concisely synthesized by the reductive decyanization of cyano-promoted intramolecular aza-Diels–Alder cycloadducts followed by aryl–aryl coupling. Cyano groups were removed from α-aminoacrylonitriles via treatment with sodium borohydride in 2-propanol in almost quantitative yields; a possible mechanism was proposed and examined using D-labeling experiments