During the past decades, synthetic organic chemistry discovered that directing group assisted C–H activation is a key tool for the expedient and siteselective construction of C–C bonds. Among the v...

Bidentate Directing Groups: An Efficient Tool in C-H Bond Functionalization Chemistry for the Expedient Construction of C-C Bonds.

ConspectusThe importance of sustainable and green synthetic protocols for the synthesis of fine chemicals has rapidly increased during the last decades in an effort to reduce the use of fossil fuel...

A Decade of Electrochemical Dehydrogenative C,C-Coupling of Aryls.

https://pubs.rsc.org/en/content/articlepdf/2019/CC/C9CC03967H

Recent advances in the synthesis of axially chiral biaryls via transition metal-catalysed asymmetric C–H functionalization

Transition metal-catalyzed aryl C-H activation is a powerful synthetic tool as it offers step and atom-economical routes to site-selective functionalization. Compared with proximal ortho-C-H activation, distal (meta- and/or para-) C-H activation remains more challenging due to the inaccessibility of these sites in the formation of energetically favorable organometallic pretransition states. Directing the catalyst toward the distal C-H bonds requires judicious template engineering and catalyst design, as well as prudent choice of ligands. This review aims to summarize the recent elegant discoveries exploiting directing group assistance, transient mediators or traceless directors, noncovalent interactions, and catalyst and/or ligand selection to control distal C-H activation.

Arene diversification through distal C(sp2)-H functionalization.

Transition metal-catalyzed enantioselective functionalization of C-H bond, the most abundant functionality in organic molecules, has emerged as an expedient synthetic approach to streamline the synthesis of complex chiral molecules. Despite significant progress, traditional directing group-enabled strategies require additional steps for the installation and removal of directing groups from the target molecule. The recently developed asymmetric C-H functionalization using chiral transient directing groups (cTDGs) offers a promising alternative that can circumvent this obstacle and therefore simplify the process. In this Minireview, we briefly discuss the advent and recent advances of this emerging concept, with an emphasis on discussing the creation of various stereogenic centers and the developments of cTDGs. Applications in natural product synthesis and ligand derivatizations are also discussed. We hope this Minireview will highlight the great potential of this strategy and help to inspire further endeavors.

Transition Metal-Catalyzed Enantioselective C−H Functionalization via Chiral Transient Directing Group Strategies

Among numerous solvents available for chemical transformations, 1,1,1,3,3,3-hexafluoro-2-propanol (popularly known as HFIP) has attracted enough attention of the scientific community in recent years. Several unique features of HFIP compared to its non-fluoro analogue isopropanol have helped this solvent to make a difference in various subdomains of organic chemistry. One such area is transition metal-catalyzed C-H bond functionalization reactions. While, on one side, HFIP is emerging as a green and sustainable deep eutectic solvent (DES), on the other side, a major proportion of Pd-catalyzed C-H functionalization is heavily relying on this solvent. In particular, for distal aromatic C-H functionalizations, the exceptional impact of HFIP to elevate the yield and selectivity has made this solvent irreplaceable. Recent research studies have also highlighted the H-bond-donating ability of HFIP to enhance the chiral induction in Pd-catalyzed atroposelective C-H activation. This perspective aims to portray different shades of HFIP as a magical solvent in Pd-catalyzed C-H functionalization reactions.

/pdf/hexafluoroisopropanol-the-magical-solvent-for-pd-catalyzed-c-24ld9lgihk.pdf

Hexafluoroisopropanol: the magical solvent for Pd-catalyzed C-H activation.

1,1,1,3,3,3-Hexafluoroisopropanol (HFIP) has emerged as an attractive tool in developing and facilitating C–H activation/functionalizations. The hydrogen bond donating ability of this solvent coupled with its enhanced acidity and reduced nucleophilicity has played an integral part in boosting the reactivity and stereoselectivity of C–H functionalization reactions. Several C–H activation reactions necessitate the requirement of HFIP which plays a central role in developing these methodologies. Herein, this report showcases the importance of HFIP in developing C–H activation reactions in organic synthesis.

Role of hexafluoroisopropanol in C–H activation

Transition-metal-catalyzed C–H allylation reactions

In the domain of synthetic chemistry, C–H bond activation has always remained in the spotlight for researchers over the last few decades. Although different strategies have been employed to chemically trigger unactivated C–H bonds, transition metal catalyzed directing group (DG) aided C–H bond activation is the most explored pathway of all because of its ability to perform diverse site selective functional metamorphosis. Despite its popularity, tedious synthetic methodology requiring additional steps for the installation and removal of DGs from the target substrate diminishes its efficacy. However, replacement of directing groups by transient directing groups (tDGs) reduces the hurdle to a greater extent without compromising the product yield and selectivity. In this report we have depicted the intense journey of transient directing groups with three (Rh, Ru, and Pd) prevalent second row transition metals.

/pdf/combining-transition-metals-and-transient-directing-groups-1yzt63g4wy.pdf

Trisha Bhattacharya

Papers

Arene diversification through distal C(sp2)-H functionalization.

Hexafluoroisopropanol: the magical solvent for Pd-catalyzed C-H activation.

Role of hexafluoroisopropanol in C–H activation

Transition-metal-catalyzed C–H allylation reactions

Combining transition metals and transient directing groups for C–H functionalizations