A copper-catalyzed intramolecular amidation of unactivated C(sp³)−H bonds to construct indoline derivatives has been developed. Such an amidation proceeded well at primary C−H bonds preferred to secondary C−H bonds. The transformation owned a broad substrate scope. The corresponding indolines were obtained in good to excellent yields. N-Formal and other carbonyl groups were suitable and were easily deprotected and transformed into methyl or long-chained alkyl groups. Preliminary mechanistic studies suggested a radical pathway.

In the context of transition-metal-catalyzed CH functionalization, directing-group strategy was developed for the improvement of chemical reactivity and selectivity. Recently, to avoid the inherent limitations of traditional mono-role directing groups, a dual-role oxidizing-directing-group strategy was developed, in which the directing group acts both as directing group and oxidant. Herein, we report a multirole directing group, which possesses multiple reactive sites, exhibits unique reactivity and selectivity, and leads to four different types of products from a single starting material through rhodium-catalyzed CH activation/alkyne annulation reactions. The excellent product diversity and regio- and redox selectivity were well controlled by the tuning of solvents and oxidants.

Biaryl skeletons were directly constructed via palladium-catalyzed ortho-arylation of N,N-dimethyl benzylamine with aryl boronic acids with high efficiency and high regioselectivity under open-flask conditions. The N,N-dimethylaminomethyl group was first applied as a directing group in such an oxidative coupling. Various substrates proved to be efficient coupling partners, furnishing the corresponding ortho-monoarylated or -diarylated arenes in moderate to good yields under mild conditions.

A novel bidentate α-amino oxazolinyl directing group has been developed. Different from previous directing groups, this newly designed directing group was easily prepared from amino acids and modified in structure. This auxiliary preferentially effects functionalization at secondary C(sp³)H bonds, rather than at aryl C(sp²)H bonds. The diastereoselectivity of direct arylation between geminal secondary C(sp³)H bonds in linear molecules has also been realized for the first time with a chiral directing group by remote chirality relay. Two diastereoisomers are produced with the same chiral source by changing the substituents of substrates and aryl halides.

A rhodium(III)-catalyzed cross-coupling of benzyl thioethers and aryl carboxylic acids through the two directing groups is reported. Useful structures with diverse substituents were efficiently synthesized in one step with the cleavage of four bonds (CH, CS, OH) and the formation of two bonds (CC, CO). The formed structure is the privileged core in natural products and bioactive molecules. This work highlights the power of using two different directing groups to enhance the selectivity of a double CH activation, the first of such examples in cross-oxidative coupling.

A rhodium(III)-catalyzed cross-coupling of benzyl thioethers and aryl carboxylic acids through the two directing groups is reported. Useful structures with diverse substituents were efficiently synthesized in one step with the cleavage of four bonds (CH, CS, OH) and the formation of two bonds (CC, CO). The formed structure is the privileged core in natural products and bioactive molecules. This work highlights the power of using two different directing groups to enhance the selectivity of a double CH activation, the first of such examples in cross-oxidative coupling.

A palladium catalyzed ortho-alkoxylation of aryl CH bond was accomplished with primary and secondary alcohols as alkoxylation reagents and with triazole as new directing group. This transformation has a good functional group tolerance and is not sensitive to moisture and air.

A Rh^I-catalyzed direct C2-arylation of indoles with diversely substituted aryl carboxylic acids has been developed using 2-pyrimidyl group as an easily installable and readily removable N-directing group. The reaction proceeded smoothly without the need for any external oxidants under relatively mild conditions to produce the C2-arylated indoles in high yields with excellent regioselectivity. A range of functional groups in both coupling partners were tolerated regardless of their electronic properties and positions. With the assistance of the 2-pyrimidyl group, these C2-functionalized products could further undergo C7-arylation to give the C7-aryl indole products. Mechanistic evidence supports that the reaction involves a decarbonylation step, and the carboxylic acids could be activated in situ by treatment with (tBuCO)₂O to generate the active anhydrides.

Organoborane compounds are among the most commonly employed intermediates in organic synthesis and serve as crucial precursors to alcohols, amines, and various functionalized molecules. A simple palladium-based system catalyzes the conversion of primary C(sp³)H bonds in functionalized complex organic molecules into alkyl boronate esters. Amino acids, amino alcohols, alkyl amines, and a series of bioactive molecules can be functionalized with the use of readily available and removable directing groups in the presence of commercially available additives, simple ligands, and oxygen (O₂) as the terminal oxidant. This approach represents an economic and environmentally friendly method that could find broad applications.

3,4-Dihydroquinolinones were synthesized by the palladium-catalyzed, oxidative-addition-initiated activation and arylation of inert C(sp³)H bonds. Pd(OAc)₂ and P(o-tol)₃ were used as the catalyst and ligand, respectively, to improve the efficiency of the reaction. A further advantage of this reaction is that it could be performed in air. A relatively rare seven-membered palladacycle was proposed as a key intermediate of the catalytic cycle.

3,4-Dihydroquinolinones were synthesized by the palladium-catalyzed, oxidative-addition-initiated activation and arylation of inert C(sp³)H bonds. Pd(OAc)₂ and P(o-tol)₃ were used as the catalyst and ligand, respectively, to improve the efficiency of the reaction. A further advantage of this reaction is that it could be performed in air. A relatively rare seven-membered palladacycle was proposed as a key intermediate of the catalytic cycle.

Organoborane compounds are among the most commonly employed intermediates in organic synthesis and serve as crucial precursors to alcohols, amines, and various functionalized molecules. A simple palladium-based system catalyzes the conversion of primary C(sp³)H bonds in functionalized complex organic molecules into alkyl boronate esters. Amino acids, amino alcohols, alkyl amines, and a series of bioactive molecules can be functionalized with the use of readily available and removable directing groups in the presence of commercially available additives, simple ligands, and oxygen (O₂) as the terminal oxidant. This approach represents an economic and environmentally friendly method that could find broad applications.

The first example of the transition-metal-catalyzed direct intermolecular C–H bond addition to ketones was achieved by using a rhodium catalyst. A significant influence of the directing group on the reactivity was observed, and sterically more hindered directing groups could promote the reaction. In addition, intermolecular hydrogen bonding played a role in stabilizing the product. The substrate scope for the quinoline derivatives was very good.

We report three transformations: 1) direct transformation from biarylmethanols into biarylmethylamines; 2) direct transformation from one biarylmethanol into another biarylmethanol; 3) direct transformation from allylic alcohols into allylic amines. These transformations are based on pyridyl-directed Rh-catalyzed CC bond cleavage of secondary alcohols and subsequent addition to CX (X=N or O) double bonds. The reaction conditions are simple and no additive is required. The driving force of CC bond cleavage is the formation of the stable rhodacycle intermediate. Other directing groups, such as the pyrazolyl group, can also be used although it is not as efficient as the pyridyl group. We carried out in-depth investigations for transformation 1 and found that: 1) the substrate scope was broad and electron-rich alcohols and electron-deficient imines are more efficient; 2) as the leaving group, aldehyde had no significant impact on either the CC bond cleavage or the whole transformation; 3) mechanistic studies (intermediate isolation, in situ NMR spectroscopic studies, competing reactions, isotopic labeling experiments) implied that: i) The CC cleavage was very efficient under these conditions; ii) there is an equilibrium between the rhodacycle intermediate and the protonated byproduct phenylpyridine; iii) the addition step of the rhodacycle intermediate to imines was slower than the CC cleavage and the equilibrium between the rhodacycle and phenylpyridine; iv) the whole transformation was a combination of two sequences of CC cleavage/nucleophilic addition and CC cleavage/protonation/CH activation/nucleophilic addition, with the latter being perhaps the main pathway. We also demonstrated the first example of cleavage of an C(alkenyl)C(benzyl) bond. These transformations showed the exchange (or substitution) of the alcohol group with either an amine or another alcohol group. Like the “group transplant”, this method offers a new concept that can be used to directly synthesize the desired products from other chemicals through reorganization of carbon skeletons.

Enol and phenol functionalities are very common in organic molecules. Utilization of these materials is very appealing in organic synthesis because they are important alternatives to organohalides in cross-coupling reactions. In this review, we summarize the transition-metal-catalyzed cross-coupling of enol- and phenol-based electrophiles, including phosphates, sulfonates, ethers, carboxylates, and phenolates.