In Situ Generation of Ru-Based Metathesis Catalyst. A Systematic Study

Stereoselective Cyclopropanation of Enamides via C―C Bond Cleavage of Cyclopropenes

This work describes a straightforward protocol for the stereoselective synthesis of vinylcyclopropylamides in high E/Z and syn/anti ratios by cyclopropanation of N-tosyl substituted enamides with cyclopropenes in the presence of...

Simple synthesis of [Ru(CO3)(NHC)(p-cymene)] complexes and their use in transfer hydrogenation catalysis

A novel, efficient and facile protocol for the synthesis of a series of [Ru(NHC)(CO₃)(p-cymene)] complexes is reported. This family of Ru-NHC complexes was obtained from imidazol(in)ium tetrafluoroborate or imidazolium hydrogen carbonate salts in moderate to excellent yields, employing sustainable weak base. The ruthenium complexes were successfully utilized in the transfer hydrogenation of ketones as highly active multifunctional catalysts.

A New ternary organometallic Pd(ii)/Fe(iii)/Ru(iii) self-assembly monolayer: the essential ensemble synergistic for improving catalytic activity

The synergistic catalytic effect in a hetero-trimetallic catalytic monolayer is one of the intriguing topics because the additive effects of the second or third component play an important role in improving the activity. In this paper, a new Schiff-base organometallic nanosheet containing Pd/Fe/Ru immobilized on graphene oxide (GO@H-Pd/Fe/Ru) was prepared and characterized. The catalytic performance of GO@H-Pd/Fe/Ru and synergistic effect were systematically investigated. GO@H-Pd/Fe/Ru was found to be an efficient catalyst with higher turnover frequency (TOF) (26 892 h-1) and stability with recyclability of at least 10 times in the Suzuki-Miyaura coupling reaction. The deactivation mechanism was caused by the aggregation of the active species, loss of the active species, the changes of the organometallic complex, and active sites covered by adsorbed elements during the catalytic process. GO@H-Pd/Fe/Ru was a heterogeneous catalyst, as confirmed by kinetic studies with in situ FT-IR, thermal filtration tests and poisoning tests. The real active center containing Pd, Ru and Fe arranged as Fe(iii)-Ru(iii)-Pd(ii)-Fe(iii) was proposed. Although Ru(iii) and Fe(iii) were shown to be less active or inactive, the addition of Fe and Ru could effectively improve the entire activity by their ''indirect'' function, in which Fe or Ru made Pd more negative and more stable. The ensemble synergistic effect between metals, the ligand and support was described as a process in which the electron was transferred from GOvia ligand to Ru, and then to Pd or from Fe to Pd to make Pd more negative, promoting the oxidation addition with aryl halide. Also, the vicinity of Ru around Pd as the promoter adsorbed aryl boronic acid, which facilitates its synergism to react with the oxidation intermediate to the trans-metallic intermediate.

A simple and efficient in situ generated copper nanocatalyst for stereoselective semihydrogenation of alkynes

Development of a simple, effective, and practical method for (Z)-selective semihydrogenation of alkynes has been considered necessary for easy-to-access applications at organic laboratory scales. Herein, (Z)-selective semihydrogenation of alkynes was achieved using a copper nanocatalyst which was generated in situ simply by adding ammonia borane to an ethanol solution of copper sulfate. Different types of alkynes including aryl-aryl, aryl-alkyl, and aliphatic alkynes were selectively reduced to (Z)-alkenes affording up to 99% isolated yield. The semihydrogenation of terminal alkynes to alkenes and gram-scale applications were also reported. In addition to eliminating catalyst preparation, the proposed approach is simple and practical and serves as a suitable alternative method to the conventional Lindlar catalyst.

Grubbs Metathesis Enabled by a Light-Driven gem-Hydrogenation of Internal Alkynes

[(NHC)(cymene)RuCl2 ] (NHC=N-heterocyclic carbene) complexes instigate a light-driven gem-hydrogenation of internal alkynes with concomitant formation of discrete Grubbs-type ruthenium carbene species. This unorthodox reactivity mode is harnessed in the form of a "hydrogenative metathesis" reaction, which converts an enyne substrate into a cyclic alkene. The intervention of ruthenium carbenes formed in the actual gem-hydrogenation step was proven by the isolation and crystallographic characterization of a rather unusual representative of this series carrying an unconfined alkyl group on a disubstituted carbene center.