Cobalt(III)‐Catalyzed [4+2] Annulation of Heterobicyclic Alkenes by sp² C−H Activation

Abstract

An efficient and convenient cobalt(III)‐catalyzed highly diastereoselective strategy was demonstrated for the synthesis of epoxybenzophenanthridinone derivatives. The sp2 C−H activation of N‐methoxybenzamides and their annulation reaction with 7‐oxa/aza benzonorbornadienes proceeds under mild conditions and exhibits excellent functional group tolerance. In addition, the products were transformed to biologically relevant phenanthridinones by an acid‐catalyzed ring opening/aromatization sequence.

Rh(III)‐Catalyzed Ring‐Opening Addition of Azabenzonorbornadienes with Cyclic N‐Sulfonyl Ketimines via C−H Bond Activation

“…[9] Cheng and co-workers have described the cobalt-catalyzed diastereoselective [3 + 2] annulation of aromatic/vinylic amides with bicyclic alkenes [10] and the ring-opening addition of arenes to oxabenzonorbornadienes. [13] Besides, the [4 + 2] cycloaddition, [14] 2-naphthylaton, [15] have also been reported by other groups. [12] During the preparation of this manuscript, Li and co-workers reported a rhodium(III)catalyzed high efficiency enantioselective coupling of indoles and azabenzonorbornadienes by CÀ H activation/desymmetrization.…”

“…[12] During the preparation of this manuscript, Li and co-workers reported a rhodium(III)catalyzed high efficiency enantioselective coupling of indoles and azabenzonorbornadienes by CÀ H activation/desymmetrization. [13] Besides, the [4 + 2] cycloaddition, [14] 2-naphthylaton, [15] have also been reported by other groups. During our long interest in the asymmetric ring-opening (ARO) reactions of bicyclic alkenes, [16] we became interested in the CÀ H functionalization of arenes with bicyclic alkenes.…”

“…Based on reported literatures of the CÀ H functionalizations of arenes with bicyclic alkenes [7][8][9][10][11][12][13][14] and the results of mechanism study experiments, a proposed mechanism is shown in Figure 2. The catalytic reaction may initiate by the generation of active Rh(III) species A from ligand exchange with AgPF 6 and NaOAc.…”

Rh(III)‐Catalyzed Denitrogenative [4+2] Annulation of Benzamides and 3‐Diazoindolin‐2‐imines: Expedient Access to Indolo[2,3‐c] isoquinolin‐5‐ones

“…In an another transformation, Lee group described a rhodium‐catalyzed cyclization of sulfoximines and 3‐diazoindolin‐2‐imines to generate indolo‐1,2‐benzothiazines via N–H/C–H activation of S‐aryl sulfoximines . Recently, we developed an efficient Co(III)‐catalyzed strategy for the synthesis of benzophenanthridinone derivatives via sp 2 C−H activation of N ‐methoxybenzamides followed by annulation with 7‐oxa/aza benzonorbornadienes (Scheme b) . Our continuous interest in both C−H activation and rhodium carbenoids, prompted us to test benzamides in Rh(III)‐catalyzed C−H annulation reaction with diazoimines and herein, we report a facile coupling of N ‐methoxybenzamides and 3‐diazoindolin‐2‐imines for accessing biologically important indolo[2,3‐ c ]isoquinolin‐5‐ones.…”

Cp*Co(III)-Catalyzed C–H Hydroarylation of Alkynes and Alkenes and Beyond: A Versatile Synthetic Tool

“…In this case, the Co(I) species formed after reductive elimination is reoxidized to the catalytically active Cp*Co(III) species by the methoxyl group attached to the nitrogen, which acts as an internal oxidant ( Scheme 32 ). 53 After some kinetic isotope effect (KIE) and deuterium exchange experiments, the authors concluded that the C–H activation step was irreversible and not rate determining.…”