A facile and efficient route for the synthesis of tetrasubstituted imidazoles from amidines and chalcones via FeCl3/I2-catalyzed aerobic oxidative coupling has been developed. This new strategy is featured by high regioselectivity and yields, good functional group tolerance, and mild reaction conditions.

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A cobalt­(III)-catalyzed, redox-neutral, intermolecular carboamination of propiolates and bicyclic alkenes was developed. This non-annulative coupling strategy features atom economy, high regioselectivity, good yields, and functional groups tolerance. Such a carboamination reaction was applied to modified phenols from the corresponding phenols under mild conditions.

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An oxyacetamide-directed Rh­(III)-catalyzed Z-type alkenyl C–H functionalization through a rare exo-rhodacyle intermediate is described, forming multisubstituted dienes and allenes. A variety of alkenes and propargylic carbonate coupling partners are suitable for this transformation with high regio- and stereoselectivity. The synthetic utility is demonstrated by the selective late-stage modification of the Z-type natural products as well as the synthesis of the unnatural β-amino acid.

Transition-metal-catalyzed C-H functionalization reactions, assisted by directing groups (DGs), have become some of the most powerful strategies to form C-C and C-X (X = O, N, S, etc.) bonds. It has brought about a revolution in the synthesis of drugs and natural products, and the method is widely applicable in the fields of material chemistry and pharmaceutical industry. This strategy has mainly focused on regioselective C -H functionalization of amides, esters, carbamates, and enamides with DGs to form C-C and C-X bonds. Since these DGs are relatively stable, they must be removed by other methods when the reaction is completed. Therefore, the use of a traceless DG is one of the important challenges for transition-metal-catalyzed C-H functionalization. Recently, N-phenoxyamide has been attracting significant research attention as a versatile DG. Oxyacetamide (O-NHAc) is one of the most versatile functionalities for directed C-H functionalization cascades, such as the internal oxidation with N-O bond cleavage. The O-NHAc has been reported as a superb DG for redox-neutral C-H activation/annulation cascade reactions to synthesize phenol and complex heterocyclic scaffolds by coupling with alkynes, alkenes, heteroarenes, and diazo compounds. However, for the external oxidation with preservation of the N-O bond, e.g. when a stoichiometric external oxidant is present, N-phenoxyamides could react with aldehydes or α, β-unsaturated aldehydes. In addition, the solvent can control the chemoselectivity. In this minireview, the C-H bond functionalization of N-phenoxyamide is divided into five categories according to the different substrates, viz. alkenes, alkynes, diazo, and other compounds and intramolecular C-H bond activation reactions. Based on experimental and theoretical research results, the reaction mechanism was discussed. In the first part, we summarize the ortho-alkylation, alkenylation, and cyclization of N-phenoxyamide with olefins. In the second part, we present the Rhand Ir-catalyzed C-H activation or cyclization of N-phenoxyamide with alkanes to synthesize phenol or benzofuran compounds. In the third part, we describe the synthesis of phenolic compounds functionalized by Rh-catalyzed diazo compounds by carbene intermediates and N-phenoxyamides. The forth part summarizes the C-H activation/annulation reaction using aldehydes, heterocyclic aromatic, and sulfur reagents as substrates. The last part of the paper generalizes the intramolecular ortho-hydroxylation and ortho, para-amidation reactions.

Be a powerful technique for convenient detection of pH change in living cells, especially at subcellular level, fluorescent probes has attracted more and more attention. In this work, we designed and synthesized three rhodamine lactam modulated fluorescent probes RS1, RS2 and RS3, which all respond sensitively toward weak acidity (pH range 4-6) via the photophysical property in buffer solution without interference from the other metal ions, and they also show ideal pKa values and excellent reversibility. Particularly, by changing the lone pair electrons distribution of lactam-N atom with different conjugations, RS2 and RS3 exhibit high quantum yield, negligible cytotoxicity and excellent permeability. They are suitable to stain selectively lysosomes of tumor cells and monitor its pH changes sensitively via optical molecular imaging. The above findings suggest that the probes we designed could act as ideal and easy method for investigating the pivotal role of H(+) in lysosomes and are potential pH detectors in disease diagnosis through direct intracellular imaging.

Herein, the Rh-catalyzed consecutive C−H bond olefination/annulation/olefination cascade, tandemly directed by sulfonamide and ester groups, has been developed under mild conditions with the assistance of 1-adamantane carboxylic acid. A seven-membered metallacycle including an ester group was preferred to the five-membered one including a sulfonamide group for the third C−H activation. In this transformation, the Rh catalyst exhibits its high reactivity by catalyzing a triple C−H activation process with a low catalyst loading at 50 °C. This method can be applied in the construction of various pharmaceutical derivatives.