Base Metal Catalysis in Directed C(sp³)−H Functionalisation

Abstract

Directed C(sp 3)-H functionalization has made enormous progress in recent years, but has largely been restricted to catalysis using noble metals, particularly palladium. However, since 2013, there have been prominent advances that exploit the reactivity of abundant first row transition metals for a multitude of new bond formations. The use of base metal catalysis for C-H functionalization can provide huge advantages in terms of cost and sustainability compared to methods using noble metals. This review covers all examples, to end 2018, of auxiliary assisted, base metal catalyzed C(sp 3)-H functionalization reactions. Successful examples are reported with Fe, Co, Ni and Cu catalysis with monodentate or bidentate directing groups for C-N, CO , C-S and CC bond forming reactions. This review aims to highlight the current state of this field and potential for expansion and so scope and limitations are highlighted. Notably, examples to date have required sterically activated α-disubstituted substrates, particularly propanamide derivatives with bidentate directing groups, such as 8-aminoquinoline amides. Monodentate quinoline and thioamide directing groups have also been used with Co catalysis for C-N and CC bond formations. Mechanistic details are provided to outline the nature of the proposed organometallic intermediates and potential reaction pathways. We hope this review will stimulate further development in this growing and important field.

Catalytic C–H to C–M (M = Al, Mg) bond transformations with heterometallic complexes

“…Furthermore the presence of directing groups is typically used to achieve high site selectivity. 4 To address these limitations, a number of new base-metal catalysts [5][6][7] and new approaches to selectivity control, e.g. through non-covalent interactions, have recently emerged.…”

Amide-Directed Rhodium-Catalyzed Chain-Walking Hydrothiolation of Internal Alkenes

“…Given the ubiquitous existence of sp 3 -hybridized backbones in organic molecules, direct C­(sp 3 )–H functionalization has emerged as a crucial strategy for the formation of C­(sp 3 )–C or C­(sp 3 )–heteroatom bonds with minimal reaction steps. − This method has been profoundly developed through transition-metal-mediated C­(sp 3 )–H bond cleavage, presenting an effective alternative to traditional cross-coupling reactions. However, this approach often requires an oxidant to modulate the redox level of the reaction process upon introducing nucleophiles, − which diminish atom economy.…”

Mn- and Co-Catalyzed Aminocyclizations of Unsaturated Hydrazones Providing a Broad Range of Functionalized Pyrazolines

“…Catalysis by first-row transition metals has gained significant attention because of their low cost and natural abundance. 43 The use of manganese and cobalt catalysis remains relatively underexplored for olefin functionalizations in comparison with other transition metals such as copper, palladium, and nickel, 45 − 47 yet it offers great opportunities. We have been inspired by one of the earliest examples of preparatively useful cobalt-catalyzed olefin functionalization, namely, the Mukaiyama hydration, 48 , 49 and related processes.…”