Redox‐Neutral Synthesis of Polycyclic Azaheterocycles via Cobalt‐Catalyzed Hydroarylation/Annulation of Maleimides

Abstract

Herein, we report a cobalt-catalyzed hydroarylation of maleimides followed by an annulation sequence for the synthesis of polycyclic azaheterocycles in one pot. The reaction proceeds under redox-neutral conditions and is compatible with various functional groups. Notably, the asprepared product exhibits potential photophysical properties.

Redox-neutral C–H annulation strategies for the synthesis of heterocycles via high-valent Cp*Co(iii) catalysis

“…In 2022, Chen and Lv reported a Cp*Co( iii )-catalyzed redox-neutral hydroarylation/annulation strategy for the synthesis of polycyclic azaheterocycles starting from benzimidates and maleimides (Scheme 49). 58 The protocol required the AgSbF 6 additive with acetic acid in DCE solvent at 100 °C for 16 h. The protocol tolerated a wide range of sensitive functional groups such as –F, –Cl, –Br, –Ac, etc. The desired products were also furnished with strongly electron-withdrawing substituents such as –NO 2 , –CF 3 , etc.…”

Recent Advances in the 3 d‐Transition‐Metal‐Catalyzed Synthesis of Isoquinolines and its Derivatives

“…In 2022, Chen and coworkers [55] reported isoquinoline‐fused pyrrolidones 70 synthesis via a Co‐mediated hydroarylation and annulation sequential reactions of benzimidates 68 with maleimides 69 (Scheme 27). In this protocol, 10 mol % of Cp*Co(CO)I 2 catalyst was utilized along with 30 mol % of AgSbF 6 additive and 1 equiv.…”

“…Alkyne diones 63 containing different substituents also produces the desired products 64 in decent yields. Mechanistically, Co-complex on reaction with AgOAc generated active Co-complex Prabhu and coworkers [54] utilized benzamides 65 and 4-hydroxy-2-alkynoates 66 for synthesizing a series of 1,4-dihydrofuro [3,4- In 2022, Chen and coworkers [55] reported isoquinoline-fused pyrrolidones 70 synthesis via a Co-mediated hydroarylation and annulation sequential reactions of benzimidates 68 with maleimides 69 (Scheme 27). In this protocol, 10 mol % of Cp*Co(CO)I 2 catalyst was utilized along with 30 mol % of AgSbF 6 additive and 1 equiv.…”

Cobalt‐Catalyzed Annulation of Benzimidates or NH‐Benzaldimines with Ynamides: Synthesis of 1‐Alkoxy‐ and 1‐Alkyl‐3‐Aminoisoquinolines

“…Lv and Chen later advantageously utilized a similar strategy for the synthesis of fused-ring heterocycles (Scheme 1c). [19] While examples of metallocatalyzed benzimidate annulation reactions with alkynes or alkenes are well documented, the use of ynamide, an Ncontaining polarized unsymmetrical alkyne, remains rare. Recently, Sahoo reported a cobalt-catalyzed thioamide-directed C(arene)À H annulation with ynamide, leading to 2-amidoindenones (Scheme 1d).…”