10.1002/anie.202007030
The study presents a novel light-driven approach to Grubbs metathesis, facilitated by the gem-hydrogenation of internal alkynes using [(NHC)(cymene)RuCl2] (NHC = N-heterocyclic carbene) complexes. This method results in the formation of discrete Grubbs-type ruthenium carbene species, which can be harnessed for a "hydrogenative metathesis" reaction that converts enyne substrates into cyclic alkenes. The research explores the unique reactivity of these complexes under UV irradiation, leading to the efficient formation of various cycloalkene products. The study also discusses the potential and limitations of this new catalyst system, as well as providing experimental evidence for the formation of Grubbs-type carbenes through alkyne gem-hydrogenation. This innovative method offers a non-canonical entry into the field of metathesis chemistry, expanding the scope of catalytic hydrogenation and Grubbs catalysis.
10.1021/ja075547t
The research focuses on the synthesis, characterization, and electrochemical behavior of mononuclear ruthenium complexes with vinyl, styryl, and vinylpyrenyl ligands. These complexes were designed to investigate the effects of extending the π-system of the vinyl ligand, manipulating the electron density at the metal atom, and varying the degree of coordinative saturation at the metal atom on bonding, anodic behavior, and the metal versus ligand contribution to the redox-orbitals. The reactants used in the synthesis include ruthenium hydride complexes, terminal alkynes, and various phosphine ligands. The complexes were characterized using spectroscopic methods such as multinuclear NMR, IR, electronic spectroscopy, and X-ray crystallography. Electrochemical analyses, including cyclic voltammetry, IR-spectroelectrochemistry, and ESR spectroscopy, were employed to study the redox behavior and electronic structure of the complexes. The experimental findings were further supported by quantum chemical calculations, which provided insights into the metal versus ligand contributions to the frontier molecular orbitals and the nature of the oxidation processes.
10.1021/ol030031+
The research describes a regio- and stereoselective ruthenium-catalyzed hydrovinylation of 1,3-dienes, which is a C-C bond-forming reaction that uses ethylene as a cheap feedstock and proceeds in an atom-economical manner. The study focuses on the addition of ethylene to 1,3-dienes and 1-vinylcycloalkenes, catalyzed by two ruthenium complexes, resulting in the formation of 3-methyl-1,4-dienes. The reaction is particularly significant for a steroidal-based 1-vinylcycloalkene, as it yields a product with a 20(S) configuration, which is the opposite of most naturally occurring steroids. The chemicals used in the process include ethylene, 1,3-dienes, 1-vinylcycloalkenes, and two ruthenium catalysts, which are crucial for the selective addition reaction. The study concludes that this hydrovinylation reaction has potential for synthetic applications, especially in generating side chains with the 20(S) configuration, which is valuable for the preparation of nonnatural vitamin D3 analogues and other pharmaceutically relevant compounds.
10.1021/ic50177a011
The research focuses on the synthesis and characterization of new dithioformato complexes of platinum metals, specifically ruthenium, osmium, and iridium. The purpose of the study was to explore the "insertion" of carbon disulfide into platinum metal-hydrogen bonds, leading to the formation of a range of dithioformato complexes. The researchers used various chemical species, including [MX(S2CH)(CO)(PPh3)2] (with M being Ru or Os and X being Cl, Br, or OCOCF3), [M(S2CH)2(PPh3)2], [IrCl2(S2CH)(PPh3)2], and others, to investigate the stereochemistry and structure of these complexes. The conclusions drawn from the study were that the dithioformate anion could be detected and characterized by its IR and proton NMR spectra, and that the stereochemistry of the complexes could be assigned based on NMR patterns and couplings. The research also established that the dithioformate ligands exhibit specific NMR couplings that are valuable for determining the stereochemistry of the complexes. The study provided a comprehensive series of dithioformato complexes, contributing to the understanding of their synthesis, structure, and potential applications.
10.1016/S0040-4039(98)01432-4
The research focuses on the enantioconservative synthesis and ring closing metathesis of disubstituted dialkenic amides, which are direct precursors to Z-ethylenic pseudopeptides. The purpose of the study was to develop a method for synthesizing these amides with total conservation of enantiomeric purity, using Grubbs' ruthenium-based metathesis catalysts. The researchers successfully synthesized optically pure disubstituted dialkenic amides and cyclized them to lactams without racemization, demonstrating the feasibility of this approach. Key chemicals used in the process include 1-benzyl-prop-2-enylamine N-protected by the 2,4-dimethoxybenzyl (Dmb) group, (R)-2-benzyl-but-3-enoic acid, and the ruthenium catalysts 4a and 4b. The study concluded that the enantioconservative synthesis of N-protected diethylenic amides is possible, and that despite steric crowding, these amides can undergo smooth ring closing metathesis, leading to substituted ethylenic lactams which are direct precursors of Z-ethylenic pseudodipeptides.