Fe^III‐Catalyzed Cross‐Dehydrogenative Arylation (CDA) between Oxindoles and Arenes under an Air Atmosphere

Abstract

An efficient Fe(III)-catalyzed cross-dehydrogenative arylation (CDA) of 3-substituted oxindoles with activated arenes under an air atmosphere was developed to provide 3,3'-disubstituted oxindoles in good yields.

Graphene‐Oxide‐Catalyzed Cross‐Dehydrogenative Coupling of Oxindoles with Arenes and Thiophenols

“…This protocol was also applicable to heterocyclic aromatic compounds, producing the products 3 o – 3 p in a range of 47–67% yields. When using toluene or chlorobenzene as arene substrates, no coupling products were observed, which was consistent with the nature of Friedel‐Crafts‐type reactions . Interestingly, the carbocatalytic CH−CH coupling strategy could be successfully extended to α‐arylation of deoxybenzoins ( 3 q – 3 s ) in acceptable yields, making this carbocatalytic CDC strategy much more appealing.…”

“…Based on these findings, a plausible mechanism is proposed in Figure . First, the inherent surface acidity of GO activates the oxindole substrate 1 a so that it tautomerizes to its enol form, which is easily oxidized to the corresponding radical A′ via a single‐electron‐transfer (SET) . Then, radical A′ is oxidized to the cation species B′ by GO.…”

Transition‐metal‐free Chemoselective Oxidative C−C Coupling of the sp3 C−H Bond of Oxindoles with Arenes and Addition to Alkene: Synthesis of 3‐Aryl Oxindoles, and Benzofuro‐ and Indoloindoles

“…In this context, arylation of oxindoles via intermolecular– and intramolecular– C−C coupling using aryl halide partners catalyzed by TM‐catalysts have been well explored (Scheme ). Hg II ‐catalyzed Friedel–Crafts reactions of N ‐protected 3‐substituted 3‐hydroxyoxindoles with electron‐rich N ‐methyl indoles and electron‐rich phenols, Fe III ‐catalyzed cross‐coupling reactions of an excess amount of activated arenes such as anisole and thiophene with 3‐benzyl/phenyl‐substituted oxindoles, and Rh‐catalyzed arylation of imine‐based oxindoles with arylboronic acid have been reported in the literature …”

Iron‐catalyzed C−H Activation

“…The reaction may proceed through C–H activation catalyzed by an organoiron(III) species. Li et al . reported an efficient Fe‐catalyzed CDA of 3‐substituted oxindoles with activated arenes under air atmosphere.…”