Recent advances on nickel-catalyzed C–H bonds functionalized reactions

Abstract

The direct C-H bond functionalization has been one of the most active research fields in organic chemistry not only due to the significance in basic studies of inert C-H bond chemistry but also due to the step economy feature in potential synthetic application. In the past decades, transition-metalcatalyzed direct and selective functionalization of C-H bonds has emerged as a straightforward and environmentally friendly synthetic tool, which is also a long-standing goal that continues to drive discovery in organic synthesis. The precious late transition metals have been proved to play key roles to facilitate highly efficient transformations through C-H functionalization. However, the relatively high price, low natural abundance and partly strong toxicity limited their application. Nickel, compared to precious transition metals, is showing great potential for C-H bond functionalizations because of its low cost, unique reactivity profiles and easy availability in the earth's crust. This tutorial review summarizes the recent advances in nickel-mediated direct C-H bond functionalizations and C−C bond forming reactions.

Nickel-Catalyzed C–H Silylation of Arenes with Vinylsilanes: Rapid and Reversible β-Si Elimination

“…Increasing the temperature to 140 °C resulted in the decomposition of 1b and the formation of a black precipitate. There are several examples of nickel-catalyzed alkene hydroarylation of heterocycles; , however, instances of C–H silylation of heterocycles with any metal are limited. , A previous report of Ni-catalyzed reactions of heterocycles with H 2 CCHSiEt 3 provided solely hydroarylation products; in contrast, the reaction of H 2 CCHSiMe 3 and 1b with the heterocycle benzofuran resulted in selective silylation but also resulted in a mixture of silylation and hydroarylation products with the substrates benzoxazole and benzothiazole. The latter two substrates feature very activated C–H bonds, and catalysis was observed at temperatures as low as 60 °C.…”

Ni-Catalyzed Direct Carboxylation of an Unactivated C–H Bond with CO2

“…The mechanism of this reaction involved the formation of benzylic and aliphatic radicals and an R–Ni­(I) intermediate, and the substance scope has limitations . Although Ni-catalyzed C–H functionalization reactions have been extensively reported, to the best of our knowledge, Ni-catalyzed direct carboxylation of unactivated C–H bonds with CO 2 remains unreported. Herein, we report for the first time a Ni-catalyzed direct carboxylation of unactivated C–H bonds of indole, benzothiophene, benzofuran, and benzene under an atmospheric pressure of CO 2 .…”

An efficient nickel/silver co-catalyzed remote C–H amination of 8-aminoquinolines with azodicarboxylates at room temperature

“…Notably, the o -C–H bonds existed in these benzamides did not influence this transformation at all, which might be activated and become reaction sites under nickel catalysis. 12 Moreover, the substrates containing a substituent on the quinoline such as 2-Me, 4-Cl and 6-OMe (3ra–3ta) were also examined. Except the one with a C2 substituent which might hinder the coordination with catalysts, high yields were provided by other substrates.…”

“…As a non-precious, earth-abundant and non-toxic metal, nickel has attracted extensive attention in organic synthesis and been used as catalyst in numerous C–H functionalizations. 12 However, the examples of nickel-catalyzed C5 C–H functionalizations of quinolines are quite rare to date. 13 Examples of silver catalysis in this kind of reactions are much less.…”