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m-CAr-H bond functionalization of tertiary phosphines was developed using [Ru(p-cymene)Cl2]2 as a catalyst. Desired product structures were confirmed by single-crystal X-ray diffraction. Mechanistic experiments indicated that m-CAr-H bond functionalization was a radical reaction and that a hexagonal ruthenacycle complex was a crucial intermediate in the process. Therefore, this study provides a novel method for the late-stage meta-position modification of biphenyl monophosphine ligands.

A meta-dehydrogenative alkylation of arenes with cyclic ethers, ketones, and esters catalyzed by ruthenium is achieved in the presence of a di-tert-butyl peroxide (DTBP) oxidant. Interestingly, when quinoline and isoquinoline are employed as the directing group, or a chain ether as alkylation reagent, the system produces Minisci reaction products. Mechanistic study indicates that meta-dehydrogenative alkylation is a radical process initiated by DTBP with the assistance of a CAr-Ru bond ortho/para-directing effect.

The meta-CAr-H bond formylation of arenes has been achieved using CHBr3 as a formyl source in the presence of [Ru(p-cym)(OAc)2] as a catalyst. This method provides efficient access to the preparation of various meta-substituted aromatic compounds, such as alcohols, ethers, amines, nitriles, alkenes, halogens, carboxylic acids, and their derivatives, through transformation of the versatile formyl group. Furthermore, mechanistic studies show that the key active species is a pentagonal ruthenacycle complex.

An efficient tandem reaction of imidamides and N-hydroxycarbamates has been developed. Valuable 2-alkylbenzimidazoles could be easily obtained in up to 97% yield for more than 20 examples. The products would further streamline the synthesis of molecules, which are essential building blocks in organic synthesis and drug discovery. This protocol features high regioselectivity, efficiency, good tolerance of functional groups, and mild reaction conditions.

A method for Cu(II)-catalyzed dehydrogenative amidation of azoarene using air as the terminal oxidant was developed. Various amides, such as arylamides, alkylamides, lactams, and imides, are all effective amidation reagents and provide the desired products in moderate to excellent yields. Notably, good yields can also be obtained on a gram-scale with this amidation reaction. In this protocol of azoarene amidation, the catalyst (Cu(OAc)2) and oxidant (air) are inexpensive and readily available, and the process is highly efficient and atom economical.

A method for Pd-catalyzed aerobic oxidative reaction of quinazolinones and alkynes has been developed for sequential [4 + 2] and [3 + 2] cycloadditions to assemble a novel fused-polycyclic system containing tetrahydropyridine and dihydrofuran rings. The reaction process involves C-H and N-H bond functionalization for the formation of tetrahydropyridine and an oxygen radical cyclization for the dihydrofuran ring. This atom- and step-economical synthesis is highly efficient and has good substrate tolerance, which provides a new approach for the construction of polycyclic molecules with potential pharmaceutical interest.

meta/ortho-Selective CAr–H (di)alkylation reactions of azoarenes have been achieved via [Ru(p-cymene)Cl2]2 catalyzed ortho-metalation using various types of alkyl bromides. Particularly, dual meta-alkylation of azoarene and reduction offer an attractive strategy for the synthesis of meta-alkylanilines, which are difficult to access via traditional aniline functionalization methods.

An efficient synthesis of C4-functionalized quinolines through copper-catalyzed tandem annulation of alkynyl imines with diazo compounds is described. This transformation involves an in situ formation of allene and intramolecular electrocyclization, which features high efficiency, mild reaction conditions, easy operation, and broad functional-group tolerance. A wide variety of C4-functionalized quinolines were provided in up to 92% yield for 33 examples.

The first example of transition-metal-catalyzed ortho/meta-selective dual C–H functionalizations of arenes in one reaction is described. In this transformation, ortho-C–H chlorination and meta-C–H sulfonation of 2-phenoxypyri(mi)dines were achieved simultaneously under catalysis by [Ru(p-cymene)Cl2]2. The other reactant, namely, an arylsulfonyl chloride, played the role of both a sulfonation and chlorination reagent. More importantly, the arylsulfonyl chloride was also an oxidant in the process. Mechanistic studies indicated that six-membered ruthenacycles were the key intermediate in the reaction.