Cobalt(II)‐Catalyzed [4+2] Annulation of Picolinamides with Alkynes via C−H Bond Activation

Abstract

Ac obalt(II)-catalyzed [4+ +2] annulation of picolinamides with alkynes via CÀHb ond activation has been developed. The operationally simple annulation reaction allows for the synthesis of acyl-substituted 1H-benzoquinoline bearing multiple aromatic rings (up to 96 %y ield) without co-oxidant or other oxidation factorsu nder mild conditions. Severalc ontrol experiments were carriedo ut. This practical [4+ +2] annulation provides an efficient route to access highly functionalized compounds.

Construction of 2-(2-Arylphenyl)azoles via Cobalt-Catalyzed C–H/C–H Cross-Coupling Reactions and Evaluation of Their Antifungal Activity

“…However, most of these examples involve the functionalization of carboxylic acid substrates, and methods for transforming the C–H bonds of aromatic amines remain to be developed. Because the picolinamide motif has been reported to act as a directing group in ortho -C–H functionalization reactions of aromatic amines, we were inspired to explore the installation of aromatic heterocyclic substituents on biphenylamines via a cobalt-catalyzed picolinamide-directed C–H/C–H cross-coupling strategy (Scheme b).…”

Cobalt-Catalyzed, Directed C–H Functionalization/Annulation of Phenylglycinol Derivatives with Alkynes

“…Note! Because of restricted rotation about the amide bond, , some of the signals observed in 1 NMR are broad and coupling resolution is low; some proton signals are split (see 2D-NOESY NMR for crosspeaks). 1 H NMR (400 MHz, C 2 D 2 Cl 4 , ppm): δ 8.34 (d, J = 4.0 Hz, 1H), 7.44–7.07 (m, 11H), 7.03–6.95 (m, 1H), 6.87–6.69 (m, 5H), 6.06–5.98 (m, 1H, overlapped with C 2 D 2 Cl 4 ), 4.23–4.05 (m, 1H), 3.93 (dd, J = 10.2, 6.3 Hz, 1H), 0.98 (s, 9H), 0.13 (s, 3H), 0.08 (s, 3H).…”

“…Note! Because of restricted rotation about the amide bond, , some of the signals observed in 1 NMR are broad and coupling resolution is low; some proton signals are split. 1 H NMR spectra at 65 °C did not improve the coupling resolution quality (due to the hardware limitations, 65 °C is the maximum temperature).…”

Recent advances in radical-mediated intermolecular (4 + 2) cycloaddition

“…In 2019, a facile route was developed for picolinamide and alkynes via Co III -catalyzed (4 + 2) cycloaddition, which was disclosed by Gu, Guo, Yang and co-workers (Scheme 32). 45 From the viewpoint of the substrate scope, this method had awesome applicability and alkyl-substituted alkynes were also tolerated in this system.…”