FeCl3–Catalyzed Cascade Reactions of Cyclic Amines with 2‐Oxo‐2‐arylacetic Acids toward Furan‐2(5H)‐one Fused N,O‐Bicyclic Compounds

Abstract

AbstractA novel and efficient synthesis of furan‐2(5H)‐one fused N,O‐containing bicyclic compounds via the cascade reactions of N‐aryl substituted cyclic amines with 2‐oxo‐2‐arylacetic acids is presented. Mechanistically, the formation of the title compounds is initiated by the in situ formation of a cyclic enamine intermediate via FeCl3/di‐tert‐butyl peroxide (TBP)/oxygen (O2)‐promoted C(sp3)−H dehydrogenation of saturated cyclic amine. Nucleophilic addition of the cyclic enamine intermediate onto 2‐oxo‐2‐arylacetic acid followed by cyclization and dehydration gives the bicyclic heterocycle products. This intermolecular oxidative annulation constitutes an extension of tertiary amine‐based Mannich‐type β‐functionalization leading to a series of N,O‐bycyclic compounds in good yields with ease.magnified image