C–H bond functionalization by high-valent cobalt catalysis: current progress, challenges and future perspectives

Abstract

Over the last decade, high-valent cobalt catalysis has earned a place in the spotlight as a valuable tool for C–H activation and functionalization.

Cp*CoIII-catalyzed formal [4 + 2] cycloaddition of 2-phenyl-1H-imidazoles to afford imidazo[1,2-c]quinazoline derivatives

“…1 H NMR (500 MHz, CDCl 3 ) δ 8.56 (dd, J = 8.8, 5.9 Hz, 1H), 2H),7.72 (d,J = 1.4 Hz,1H),5H),7.41 (td,J = 8.6,2.5 Hz,1H). 13 C NMR (126 MHz, CDCl 3 ) δ 163.6 (d,J = 250.7 Hz),148.0,144.1,142.8 (d,J = 12.2 Hz),133.2,132.4,131.4,129.2,128.5,124.8 (d,J = 10.1 Hz),117.3 (d,J = 23.9 Hz),115.3(d,J = 2.0 Hz),113.7 (d,J = 22.1 Hz),113.1. HRMS (ESI): m/z (M + H + ) calcd for C 16 H 11 FN 3 , 264.0932, found: 264.0939.…”

“…In particular, Cp*Co III complexes have been used extensively in C–H functionalization reactions for the synthesis of N-heterocycles because of the avoidance of precious metal catalysts. 5 Although C–H activation methods using cobalt catalysts have been established for the efficient preparation of some N-heterocycles, such as quinazolines, 6 thiadiazine oxides, 7 pyrimidones, 8 and quinazolinones 9 (Scheme 1B), to the best of our knowledge, no example of imidazo[1,2- c ]quinazoline synthesis via Co-catalyzed C–H activation has been reported. 10,11 Herein, we report a Cp*Co III -catalyzed formal [4 + 2] cycloaddition of 2-phenyl-1 H -imidazoles to afford imidazo[1,2- c ]quinazoline derivatives with a broad substrate scope (Scheme 1C).…”

C–H bond activation and sequential addition to two different coupling partners: a versatile approach to molecular complexity

“…C-H functionalization has gained significant attention and achieved widespread application as a versatile synthetic approach utilising simple chemical inputs (Scheme 1(a)). [1][2][3][4][5][6][7][8][9][10] This strategy enables the efficient coupling of ubiquitous C-H bonds with a large variety of different functional groups under transition metal catalysed conditions, often with high atom-economy. C-H functionalization generally employs mild conditions without the need for strongly acidic or basic conditions, thus rendering it highly functional group compatible.…”

Cobalt-catalyzed carbonylative synthesis of free (NH)-tetrahydro-β-carbolinones from tryptamine derivatives

“…In recent years, cobalt catalysis has emerged as a powerful tool for C-H bond activation and functionalization due to its low cost and unique reactivity. 18 As a continuation of our interest in carbonylation, 19 we here report a cobalt-catalyzed C-H carbonylation of tryptamine derivatives with TFBen as the CO source to furnish a variety of free (NH)-tetrahydroβ-carbolinones in good yields (Scheme 2c). Notably, in this protocol, the utilization of a cobalt(II) salt provides a novel alternative in comparison with noble metal catalysts and free (NH)tetrahydro-β-carbolinone scaffolds are readily established with the in situ removal of the picolinamide directing group, which allows for further modifications.…”

“…On the basis of previous reports, 18 a plausible mechanism of the cobalt-catalyzed C-H carbonylation of tryptamine derivatives is proposed (Scheme 7). Initially, the oxidation of the Co(II) species by the Ag(I) salt followed by coordination with the tryptamine derivative 1a forms the Co(III) complex A.…”