Pincer‐based catalysts possess an exceptional balance of stability versus reactivity, aspects of fundamental interest in catalyst design. This balance has been well‐controlled by systematic ligand modifications along with the variation of the metal center. Ruthenium pincer complexes (RPCs), exhibit a versatile chemistry, serve as excellent precursors and find potential applications in many organic transformations. A large number of novel and valuable reactions has been developed using both stoichiometric and catalytic amounts of RPCs. Compared to the traditional ruthenium catalysts, pincer complexes often present high efficiency, selectivity and functional group tolerance. This review highlights different methodologies for the synthesis of RPCs and their catalytic applications for different reactions reported in the last decade. Additionally, the factors affecting the catalytic reactivity of the RPCs and the reaction mechanisms are discussed.magnified image

A strategy for the synthesis of iodocarbazoles through a tandem iodocyclization with migration and aromatization is presented. This sequential cascade process is concisely conducted at room temperature and in a short time. Moreover, the obtained halides can be further applied to palladium-catalyzed coupling reactions, which act as the important intermediates for building other valuable compounds.

Highly para-selective palladium-catalyzed direct arylation of phenols with aryl iodides was demonstrated by taking advantage of the formal inverse direct arylation strategy. A series of 4-aryl phenols were synthesised by employing water as a "green" solvent under mild reaction conditions.

Transformation of aromatic nitriles to imidazolines has been achieved under basic conditions with the electron-deficient C60 and C70 fullerenes, but not with the electron-deficient olefin of tetracyanoethylene (TCNE). In situ UV-vis-NIR indicates that the ability of RC60(-) to undergo single-electron transfer (SET) to C60 is crucial for the reaction.

The first palladium-catalyzed dearomative cyclization via a modified Catellani-type C-H functionalization has been realized. The new strategy led to a series of spiroindolenine derivatives bearing an all-carbon quaternary spirocenter from simple aryl halides and substituted indoles.

A copper-catalyzed oxidative cyclization procedure has been developed for the production of 2-sulfonated 9H-pyrrolo[1,2-a]indol-9-ones via the direct sulfonylation of N-propargyl-substituted indoles with sulfonylhydrazides and tert-butyl hydroperoxide (TBHP). This novel protocol, which tolerates a broad range of functional groups, offers a simple, efficient, and atom-economical route to a series of fluorazones in good yields under mild conditions.

[60]Fullerene derivatives with novel 1,4,9,25- and 1,4,9,12-configurations were obtained by reactions of C60 with aliphatic ketones and benzyl bromide under basic conditions. The structures of the products were determined by X-ray single-crystal diffraction and spectroscopic characterization. The reactions were rationalized by a monoenolate addition experiment and in situ vis-NIR spectroscopy.

An efficient Au­(I)-catalyzed intramolecular cascade reaction of tertiary enamides tethered an alkynyl group has been developed. The process is composed of a propargyl-claisen rearrangement and 5-exo-dig cyclization. This protocol provided a powerful method for the preparation of a variety of pentasubstituted pyrroles derivatives with excellent functional group tolerance in excellent yields. Scale-up experiment and chemical transformations of products exhibited the versatility of tertiary enamides in organic synthesis again.