3d Transition Metals for C-H Activation

C-H activation has surfaced as an increasingly powerful tool for molecular sciences, with notable applications to material sciences, crop protection, drug discovery, and pharmaceutical industries, among others. Despite major advances, the vast majority of these C-H functionalizations required precious 4d or 5d transition metal catalysts. Given the cost-effective and sustainable nature of earth-abundant first row transition metals, the development of less toxic, inexpensive 3d metal catalysts for C-H activation has gained considerable recent momentum as a significantly more environmentally-benign and economically-attractive alternative. Herein, we provide a comprehensive overview on first row transition metal catalysts for C-H activation until summer 2018.

Cobalt-Catalyzed Stereoselective Synthesis of 2,5- trans-THF Nitrile Derivatives as a Platform for Diversification: Development and Mechanistic Studies

A straightforward protocol integrating a sustainable approach for the synthesis of new 2,5- trans-THF nitrile derivatives enabling an easy diversification of its side chain scaffolds is described. The reaction tolerated different aromatic and alkyl substituents, affording the corresponding 2,5- trans-THFs in high diastereoselectivity. A detailed mechanistic study using DFT calculation reveals details of the ligand-exchange step, suggesting an inner-sphere syn attack to form the 2,5- trans stereochemistry as the most likely pathway, excluding the previous cation radical intermediate. The formation of a Co-C intermediate is suggested on the basis of the homolytic cleavage to give the previously proposed free carbon radical intermediate.

A metal-free yne-addition/1,4-aryl migration/decarboxylation cascade reaction of alkynoates with Csp3–H centers

Reactions of alkynoates with different types of radical precursors under metal-free conditions affording single-site-addition poly-substituted alkenes were reported.

Copper-Catalyzed Oxidative C-H Amination of Tetrahydrofuran with Indole/Carbazole Derivatives

A simple α-C-H amination of cyclic ether with indole/carbazole derivatives has been accomplished by employing copper(II) chloride/bipy as the catalyst system. In the presence of the di-tert-butyl peroxide oxidant, cyclic ethers such as tetrahydrofuran, 1,4-dioxane, and tetrahydropyran successfully undergo C-H/N-H cross dehydrogenative coupling (CDC) with various carbazole or indole derivatives in good-to-excellent yields.