Cobalt‐Catalyzed C−H Alkoxylation of Ferrocenes with Alcohols under Mild Conditions

Salicylaldehyde-Cobalt(II)-Catalyzed C-H Alkoxylation of Indoles with Secondary Alcohols

A straight and efficient protocol for the synthesis of hindered indole-ethers via C-H alkoxylation of indoles was developed by a cobalt-catalyzed cross-dehydrogenative coupling reaction with secondary alcohols. The selection of the salicylaldehyde-Co(II) catalyst enables the reaction to proceed under conditions without acid or base addition in the presence of limited alcohols. The protocol has broad substrate scope for both indole and secondary alcohols and exhibits good functional tolerance. The synthetic applications are proven by gram-scale reaction and further diversification of the product. Preliminary mechanistic investigations indicate that the activation of C-H bonds is not the rate-determining step of the reaction.

Recent Advances in Transition-Metal-Catalyzed C-H Functionalization of Ferrocene Amides

During the past decades, in synthetic organic chemistry, directing-group-assisted C-H functionalization is found to be a key tool for the expedient and site-selective construction of C-C and hybrid bonds. Among C-H functionalization of ferrocene derivatives, the directed group strategy is undoubtedly the most commonly used method. Compared to the other directing groups, ferrocene amides can be synthesized easily and are now recognized as one of the most efficient devices for the selective functionalization of certain positions because its metal centre permits fine, tuneable and reversible coordination. The family of amide directing groups mainly comprises monodentate and bidentate directing groups, which are categorized on the basis of coordination sites. In this review, various C-H bond functionalization reactions of ferrocene using amide directing groups are broadly discussed.

Recent advances in the synthesis of ferrocene derivatives via 3d transition metal-catalyzed C-H functionalization

In recent years, transition-metal-catalyzed C-H functionalization has gradually developed into a powerful tool for the synthesis of ferrocenes in an atom- and step-economic fashion. However, despite significant achievements, the vast majority of these C-H functionalizations required precious 4d or 5d transition metal catalysts. The use of inexpensive and sustainable 3d metals in the C-H functionalization of ferrocenes remains challenging, especially the development of asymmetric versions. Herein, we summarize the remarkable recent progress in the synthesis of ferrocenes by 3d transition metal-catalyzed C-H activation until December 2021.

Copper-catalyzed monoselective C-H amination of ferrocenes with alkylamines

A copper-catalyzed mono-selective C–H amination of ferrocenes assisted by 8-aminoquinoline is presented here. A range of amines, including bioactive molecules, were successfully installed to the ortho-position of ferrocene amides with high efficiency under mild conditions. A range of functionalized ferrocenes were compatible to give the aminated products in moderate to good yields. The gram-scale reaction was smoothly conducted and the directing group could be removed easily under basic conditions.