Biaryl scaffolds are found in natural products and drug molecules and exhibit a wide range of biological activities. In past decade, the transition metal-catalyzed C–H arylation reaction came out as an effective tool for the construction of biaryl motifs. However, traditional transition metal-catalyzed C–H arylation reactions have limitations like harsh reaction conditions, narrow substrate scope, use of additives etc. and therefore encouraged synthetic chemists to look for alternate greener approaches. This review aims to draw a general overview on C–H bond arylation reactions for the formation of C–C bonds with the aid of different methodologies, majorly highlighting on greener and sustainable approaches.

Chalcogenide motifs are present as principal moieties in a vast array of natural products and complex molecules. Till date, the construction of these chalcogen motifs has been restricted to either the use of directing groups or the employment of a large excess of electronically activated arenes, typically employed as a cosolvent. Despite being highly effective, these methods have their own limitations in the step economy and the deployment of an excess amount of arenes. Herein, we report the evolution of a catalytic system employing arene-limited, nondirected thioarylation of arenes and heteroarenes using a complimentary dual-ligand approach. The reaction is controlled by a combination of steric and electronic factors, and the utilization of a suitable ligand enables the generation of products on a complimentary spectrum to that generated by classical methods. The combination of ligands remains imperative in the reaction protocol with theoretical calculations pointing towards a monoprotected amino acid ligand being crucial in the concerted metalation deprotonation (CMD) mechanism by a characteristic [5,6]-palladacyclic transition state, while the pyridine moiety assists in the active catalyst species formation and product release. Combined experimental and computational mechanistic investigations point toward the C–H activation step being both regio- and rate-determining. Interestingly, oxidative addition of the diphenyl disulfide substrate is found to be unlikely, and an alternative transmetalation-like mechanism involving the Pd–Ag heterometallic complex is proposed to be operative.

Biaryl compounds are extremely important structural motifs in natural products, biologically active components and pharmaceuticals. Selective synthesis of biaryls by distinguishing the subtle reactivity difference of distal arene C−H bonds are significantly challenging. Herein, we describe para‐selective C−H arylation, which is acheived by a unique combination of a meta‐directing group and norbornene as a transient mediator. Upon direct meta‐C−H palladation, one‐bond relay palladation occurs in presence of norbornene and subsequently para‐C−H arylation is achieved for sulfonates, phosphonates and phenols bearing 2,6‐disubstitution patterns. The protocol is amenable to electron‐deficient aryl iodides. Multisubstituted arenes and phenols are obtained by postsynthetic modification of the products. The protocol allows the synthesis of hexa‐substituted benzene by sequential selective distal C−H functionalization.

The alarming growth in atmospheric CO2 has emerged as one of the prime concerns in the context of climate change. The power, petroleum, and construction sectors are the major contributors...

The Fujiwara–Moritani reaction using electric current is a powerful tool for the olefination of arenes by Pd-catalysed C–H activation.