Advances in Development of C–H Activation/Functionalization Using a Catalytic Directing Group

Abstract

The transition metal catalyzed direct site‐selective carbon –hydrogen functionalization is ubiquitous in organic synthesis and has reached an impressive level of sophistication and efficiency emerging as a powerful synthetic strategy for C–C bond and C–X bond formation to access various useful arylated organic molecules. For the past two decades, directing group strategy has been used for selective activation and functionalization of certain inert C–H bonds. Despite the enormous development in this field, still, the majority of systems require two redundant steps, i. e. installation and removal of DGs. To overcome these limitations, recently, traceless and multitasking groups were invented as a partial solution to DG release however installation still remains unsolved. Ideally, use of the catalytic directing group, which can be reversibly linked to the substrate and can serve as an efficient directing role would circumvent this problem and is considered as one of the most efficient and powerful strategies for the non‐activated C–H functionalization (C(sp2)–H or C(sp3)–H). In this review, we describe the enormous advances in this field for direct selective C–H functionalization without involving additional steps, i. e. installation and removal of directing groups and also discuss less explored but significant non‐covalent interactions such as hydrogen bonding or ion pairing, which helps to control the selectivity of a substrate in a catalytic organic reaction.

Rhodium(III)‐Catalyzed Synthesis of Skipped Enynes via C(sp3)–H Alkynylation of Terminal Alkenes

“…Strategies to attain regioselectivity in transition metal‐catalyzed C−H bond functionalization usually rely on anchimeric assistance, [1] either exerted by a pre‐existing directing group or by taking advantage of a transient directing group [1d, 2] . While facing atom‐ and step‐economy challenges, these approaches have been established as powerful tools for the production of value‐added products from simple precursors, [3] and in the synthesis of advanced pharmaceutical compounds [4] and natural products [5] .…”

Aqueous Palladium‐Catalyzed Direct Arylation Polymerization of 2‐Bromothiophene Derivatives

“…CH bond activation [ 1–5 ] has attracted extensive attention in organic syntheses. [ 6–11 ] Particularly, palladium‐catalyzed direct arylation involves coupling of the aryl halide with the sp 2 ‐sp 2 CH functionality to accomplish aryl–aryl bond formation.…”

Traceless Directing Groups in Sustainable Metal-Catalyzed C–H Activation

“…A subcategory of TDGs are transient directing groups, which are transiently formed during the reaction and removed in situ after the transformation. Each DG category has its own positive and negative characteristics and weak points and is chosen depending on the specific application [47,[53][54][55][56][57][58][59][60][61][62][63][64][65][66][67].…”