1142-21-8Relevant articles and documents
Cationic ruthenium alkylidene catalysts bearing phosphine ligands
Endo, Koji,Grubbs, Robert H.
, p. 3627 - 3634 (2016)
The discovery of highly active catalysts and the success of ionic liquid immobilized systems have accelerated attention to a new class of cationic metathesis catalysts. We herein report the facile syntheses of cationic ruthenium catalysts bearing bulky phosphine ligands. Simple ligand exchange using silver(i) salts of non-coordinating or weakly coordinating anions provided either PPh3 or chelating Ph2P(CH2)nPPh2 (n = 2 or 3) ligated cationic catalysts. The structures of these newly reported catalysts feature unique geometries caused by ligation of the bulky phosphine ligands. Their activities and selectivities in standard metathesis reactions were also investigated. These cationic ruthenium alkylidene catalysts reported here showed moderate activity and very similar stereoselectivity when compared to the second generation ruthenium dichloride catalyst in ring-closing metathesis, cross metathesis, and ring-opening metathesis polymerization assays.
Ru-based Z-selective metathesis catalysts with modified cyclometalated carbene ligands
Bronner, Sarah M.,Herbert, Myles B.,Patel, Paresma R.,Marx, Vanessa M.,Grubbs, Robert H.
, p. 4091 - 4098 (2014)
A series of cyclometalated Z-selective ruthenium olefin metathesis catalysts with alterations to the N-heterocyclic carbene (NHC) ligand were prepared. X-Ray crystal structures of several new catalysts were obtained, elucidating the structural features of this class of cyclometalated complexes. The metathesis activity of each stable complex was evaluated, and one catalyst, bearing geminal dimethyl backbone substitution, was found to be comparable to our best Z-selective metathesis catalyst to date.
Investigations into ruthenium metathesis catalysts with six-membered chelating NHC ligands: Relationship between catalyst structure and stereoselectivity
Endo, Koji,Herbert, Myles B.,Grubbs, Robert H.
, p. 5128 - 5135 (2013)
A series of ruthenium catalysts bearing five-membered chelating NHC architectures that exhibit very high Z-selectivity in a variety of metathesis reactions have recently been reported. It was envisioned that catalysts possessing six-membered chelates could similarly exhibit high Z-selectivity and address limitations of this methodology. We thus prepared a number of new catalysts and systematically investigated the impact of the NHC and anionic ligand on their stereoselectivity. In standard metathesis assays, only catalysts containing six-membered chelated NHC structures and η2-bound anionic ligands favored the Z-olefin products. In addition, substitution with bulkier N-aryl groups led to improved Z-selectivity. The effect of ligand structure on stereoselectivity discovered in this study will be useful in the future design of highly active and Z-selective ruthenium catalysts.
A versatile and highly Z -Selective olefin metathesis ruthenium catalyst based on a readily accessible N -heterocyclic carbene
Dumas, Adrien,Tarrieu, Robert,Vives, Thomas,Roisnel, Thierry,Dorcet, Vincent,Baslé, Olivier,Mauduit, Marc
, p. 3257 - 3262 (2018)
A ruthenium catalyst for Z-selective olefin metathesis has been synthesized from a readily accessible N-heterocyclic carbene (NHC) ligand that is prepared using an efficient, practical, and scalable multicomponent synthesis. The desired ruthenium complex
Cyclometalated Z-Selective Ruthenium Metathesis Catalysts with Modified N-Chelating Groups
Herbert, Myles B.,Suslick, Benjamin A.,Liu, Peng,Zou, Lufeng,Dornan, Peter K.,Houk,Grubbs, Robert H.
, p. 2858 - 2869 (2015)
In order to design improved ruthenium catalysts for Z-selective olefin metathesis reactions, four cyclometalated catalysts with new chelated architectures were synthesized, structurally characterized, and tested in metathesis assays. The mechanism of formation of each was explored using DFT calculations. Of note, two complexes are derived from activation of a tertiary C-H bond, and one features a four-membered chelating architecture. In addition, two dipivalate complexes that did not undergo further C-H activation were isolated and studied to elucidate information about the factors affecting cyclometalation.
Monothiolate ruthenium alkylidene complexes with tricyclic fluorinated N-heterocyclic carbene ligands
Akmalov, Timur R.,Masoud, Salekh M.,Vorobyeva, Daria V.,Dolgushin, Fedor M.,Nefedov, Sergey E.,Osipov, Sergey N.
, p. 38 - 40 (2019)
New monothiolate ruthenium alkylidene complexes bearing bulky tricyclic N-heterocyclic carbene ligands decorated with two geminal trifluoromethyl groups were synthesized. Their catalytic activity in representative olefin metathesis reactions, such as ring closing metathesis of diallyltosylamine and selfmetathesis of allylbenzene, has been evaluated.
Ruthenium-Alkylidene Complexes with Sterically Rigid Fluorinated NHC Ligands
Masoud, Salekh M.,Akmalov, Timur R.,Palagin, Konstantin A.,Dolgushin, Fedor M.,Nefedov, Sergey E.,Osipov, Sergey N.
, p. 5988 - 5996 (2018)
An efficient procedure for the preparation of novel olefin metathesis catalysts of Grubbs-Hoveyda type bearing sterically rigid NHC ligands has been developed. A preliminary evaluation of their catalytic activity has been performed on representative olefin metathesis reactions, such as RCM of malonates as well as self-metathesis of allylbenzene. As result, it was found that along with excellent robustness, new complexes demonstrate remarkable activity in metathesis of allylbenzene, outperforming commercially available Grubbs-Hoveyda catalyst in terms of yield and regioselectivity.
Continuous Flow Z-Stereoselective Olefin Metathesis: Development and Applications in the Synthesis of Pheromones and Macrocyclic Odorant Molecules**
Browne, Duncan L.,Colombel-Rouen, Sophie,Crévisy, Christophe,Curbet, Idriss,Mauduit, Marc,McBride, Tom,Morvan, Jennifer,Roisnel, Thierry
supporting information, p. 19685 - 19690 (2021/08/06)
The first continuous flow Z-selective olefin metathesis process is reported. Key to realizing this process was the adequate choice of stereoselective catalysts combined with the design of an appropriate continuous reactor setup. The designed continuous process permits various self-, cross- and macro-ring-closing-metathesis reactions, delivering products in high selectivity and short residence times. This technique is exemplified by direct application to the preparation of a range of pheromones and macrocyclic odorant molecules and culminates in a telescoped Z-selective cross-metathesis/ Dieckmann cyclisation sequence to access (Z)-Civetone, incorporating a serial array of continually stirred tank reactors.
Z-Selective Monothiolate Ruthenium Indenylidene Olefin Metathesis Catalysts
Smit, Wietse,Ekeli, Jonas B.,Occhipinti, Giovanni,Wo?niak, Bartosz,T?rnroos, Karl W.,Jensen, Vidar R.
, p. 397 - 407 (2020/02/13)
Ru-alkylidenes bearing sterically demanding arylthiolate ligands (SAr) constitute one of only two classes of catalyst that are Z-selective in metathesis of 1-alkenes. Of particular interest are complexes bearing pyridine as a stabilizing donor ligand, [RuCl(SAr)(a? CHR)(NHC)(py)] (R = phenyl or 2-thienyl, NHC = N-heterocyclic carbene, py = pyridine), which initiate catalysis rapidly and give appreciable yields combined with moderate to high Z-selectivity within minutes at room temperature. Here, we extend this chemistry by synthesizing and testing the first two such complexes (5a and 5b) bearing 3-phenylindenylidene, a ligand known to promote stability in other ruthenium-based olefin metathesis catalysts. The steric pressure resulting from the three bulky ligands (the NHC, the arylthiolate, and the indenylidene) forces the thiolate ligand to position itself trans to the NHC ligand, a configuration different from that of the corresponding alkylidenes. Surprisingly, although this configuration is incompatible with Z-selectivity and slows down pyridine dissociation, the two new complexes initiate readily at room temperature. Although their thermal stability is lower than that of typical indenylidene-bearing catalysts, 5a and 5b are fairly stable in catalysis (TONs up to 2200) and offer up to ca. 80% of the Z-isomer in prototypical metathesis homocoupling reactions. Density functional theory (DFT) calculations confirm the energetic cost of dissociating pyridine from 5a (= M1-Py) to generate 14-electron complex M1. Whereas the latter isomer does not give a metathesis-potent allylbenzene ?-complex, it may isomerize to M1-trans and M2, which both form ?-complexes in which the olefin is correctly oriented for cycloaddition. The olefin orientation in these complexes is also indicative of Z-selectivity.
