Transition metal-mediated C-H bond activation and functionalization represent one of the most straightforward and powerful tools in modern organic synthetic chemistry. Bi(hetero)aryls are privileged π-conjugated structural cores in biologically active molecules, organic functional materials, ligands, and organic synthetic intermediates. The oxidative C-H/C-H coupling reactions between two (hetero)arenes through 2-fold C-H activation offer a valuable opportunity for rapid assembly of diverse bi(hetero)aryls and further exploitation of their applications in pharmaceutical and material sciences. This review provides a comprehensive overview of the fundamentals and applications of transition metal-mediated/catalyzed oxidative C-H/C-H coupling reactions between two (hetero)arenes. The substrate scope, limitation, reaction mechanism, regioselectivity, and chemoselectivity, as well as related control strategies of these reactions are discussed. Additionally, the applications of these established methods in the synthesis of natural products and exploitation of new organic functional materials are exemplified. In the last section, a short introduction on oxidant- or Lewis acid-mediated oxidative Ar-H/Ar-H coupling reactions is presented, considering that it is a very powerful method for the construction of biaryl units and polycylic arenes.

An efficient methodology for the synthesis of unsymmetrical biheteroaryl molecules has been developed via Pd(II)-catalyzed oxidative C-H/C-H cross-coupling of heteroarenes. An inversion in reactivity and selectivity has been achieved successfully to perform the desired heterocoupling. This process allows the heterocoupling of not only electron-rich N-containing heteroarenes (e.g., xanthines, azoles, and indolizines) but also electron-poor pyridine N-oxides with various thiophenes or furans.

No abstract

The establishment of simple molecular design strategy to realize red-shifted emission while maintaining good color purity for multi-resonance induced thermally activated delayed fluorescent (MR-TADF) materials remains an appealing yet challenging...

The development of facile methods for screening organic functional molecules through C-H bond activation is a revolutionary trend in materials research. The prediction of mechanochromism as well as mechanochromic trends of luminogens is an appealing yet challenging puzzle. Here, we present a strategy for the design of mechanochromic luminogens based on the dipole moment of donor-acceptor molecules. For this purpose, a highly efficient route to 2,7-diaryl-[1,2,4]triazolo[1,5-a]pyrimidines (2,7-diaryl-TAPs) has been established through programmed C-H arylation, which unlocks a great opportunity to rapidly assemble a library of fluorophores for the discovery of mechanochromic regularity. Molecular dipole moment can be employed to explain and further predict the mechanochromic trends. The 2,7-diaryl-TAPs with electron-donating groups on the 2-aryl and electron-withdrawing groups on the 7-aryl possess a relatively small dipole moment and exhibit a red-shifted mechanochromism. When the two aryls are interchanged, the resulting luminogens have a relatively large dipole moment and display a blue-shifted mechanochromism. Seven pairs of isomers with opposite mechanochromic trends are presented as illustrative examples. The aryl-interchanged congeners with a bidirectional emission shift are structurally similar, which provides an avenue for understanding in-depth the mechanochromic mechanism.