Directed C(sp³)–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(sp³)–H functionalization reactions. Successful examples are reported with Fe, Co, Ni and Cu catalysis with monodentate or bidentate directing groups for C–N, C–O, C–S and C–C 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 C–C 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