Recent Developments in Remote Meta‐C−H Bond Functionalizations

Abstract

In the past decades, there has been a dramatic increase in the developments of novel methods for the activation/functionalization of inert C−H bonds as these protocols are not only competent, reduce the waste materials in addition to the reaction time and multiple steps but also allows the reaction to be carried out in a highly regio‐specific manner under operationally simple yet effective reaction conditions. Although, in recent years, a remarkable progress has been made in the field of ortho‐and para‐C−H bonds functionalization but to our best knowledge, the distal meta‐C−H activation/functionalization is still infancy and is yet to be explore to the advanced level. Hence, we feel that there is an urgent need to aware the research community about where the field of meta‐C−H functionalization stand at present and where it might be going in near future. To this context, we strive to compile the significant achievements made in the selective meta‐C−H bonds functionalization since 2018 to till date. More interestingly, we have also displayed an overview of the earlier reports related to the meta‐C−H activation/functionalization at the beginning of this particular manuscript, and hopefully the present review article will open diverse opportunities for the advancement of both academia as well as industry.

An Introductory Overview of C–H Bond Activation/ Functionalization Chemistry with Focus on Catalytic C(sp3)–H Bond Borylation

“…For example, the strategy can target C(sp 3 )-H bonds in cyclopropanes (Shi et al, 2019) and cyclobutanes , -C(sp 3 )-H bonds of azacycles (Chen, Yang et al, 2020), and unbiased methylene C-H bonds of acyclic amides (Yang et al, 2021) giving the corresponding boronates with excellent enantioselectivities. Remote C(sp 3 )-H bond functionalization chemistry (Qiu and Wu, 2015;Sharma, 2018) has progressed slowly compared to the activation and subsequent transformation of remote C(sp 2 )-H bonds (see: Ali and Siddiqui, 2021;Genov et al, 2020;Lu et al, 2019;Kuninobu et al, 2015). In particular, asymmetric functionalization of remote C(sp 3 )-H bonds in easily accessible organic molecules remains underdeveloped, presumably due to the entropic penalty for the formation of larger-membered metallacycles via C-H metalation (Zhang and Shi, 2021).…”

Recent Advances in Transition-Metal-Catalyzed Selective C–H Alkoxycarbonyldifluoromethylation Reactions of Aromatic Substrates

“…Although the field of alkoxycarbonyldifluoromethylation of the C-H bonds has been vigorously developed recently, the alkoxycarbonyldifluoromethylation of the meta-C-H bond remains underdeveloped and has not reached an advanced level for exploitation. 31 The alkoxycarbonyldifluoromethylation of aromatic hydrocarbons represented by nitrogen-containing directing groups (pyridyl, pyrazolyl, imidazolyl, or pyrimidinyl) has been successfully achieved with only a few transition-metal catalysts.…”

Dithieno[3,2-b:2′,3′-d]thiophene (DTT): an emerging heterocyclic building block for future organic electronic materials & functional supramolecular chemistry

“…1 Generally, heterocyclic compounds are vital molecules as they play a signicant role in biochemical elds, pharmaceutical, organic electronics, medicinal chemistry and also in the material sciences and technology etc. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] The ve membered doubly unsaturated cyclopentadiene system is a non-aromatic, whereas the ve membered heterocyclic systems viz. furan, pyrrole and thiophene having oxygen, nitrogen and sulfur, respectively are aromatic in nature as the lone pair present on the heteroatom (in unhybridized p-orbital) in these systems participate in conjugation, thereby resulting in the Huckel's aromaticity (cyclic, planar, conjugated, & (4n + 2)p electrons).…”