67191-35-9Relevant articles and documents
Large-Scale Synthesis of a Niche Olefin Metathesis Catalyst Bearing an Unsymmetrical N-Heterocyclic Carbene (NHC) Ligand and its Application in a Green Pharmaceutical Context
Czajkowska-Szczykowska, Dorota,Czarnocki, Stefan,Grela, Karol,Kajetanowicz, Anna,Ma?ecki, Pawe?,Niena?towski, Tomasz,Paw?owska, Jolanta,Szczepanik, Pawe?
supporting information, p. 15708 - 15717 (2020/12/01)
A large-scale synthesis of known Ru olefin metathesis catalyst VII featuring an unsymmetrical N-heterocyclic carbene (NHC) ligand with one 2,5-diisopropylphenyl (DIPP) and one thiophenylmethylene N-substituent is reported. The optimised procedure does not require column chromatography in any step and allows for preparation of up to 0.5 kg batches of the catalyst from simple precursors. The application profile of the obtained catalyst was studied in environmentally friendly dimethyl carbonate (DMC). Although VII exhibited low efficiency in cross-metathesis (CM) with electron-deficient partners, good to excellent results were noted for substrates featuring easy to isomerise C?C double bonds. This includes polyfunctional substrates of medicinal chemistry interest, such as analogues of psychoactive 5F-PB-22 and NM-2201 and two PDE5 inhibitors—Sildenafil and Vardenafil. Finally, a larger scale ring-closing metathesis (RCM) of a Vardenafil derivative was conducted in DMC, allowing for straightforward isolation of the expected product (23 g) in high yield and with low Ru contamination level (7.7 ppm).
Palladium-Catalyzed Atom-Transfer Radical Cyclization at Remote Unactivated C(sp3)?H Sites: Hydrogen-Atom Transfer of Hybrid Vinyl Palladium Radical Intermediates
Ratushnyy, Maxim,Parasram, Marvin,Wang, Yang,Gevorgyan, Vladimir
, p. 2712 - 2715 (2018/03/02)
A novel mild, visible-light-induced palladium-catalyzed hydrogen atom translocation/atom-transfer radical cyclization (HAT/ATRC) cascade has been developed. This protocol involves a 1,5-HAT process of previously unknown hybrid vinyl palladium radical intermediates, thus leading to iodomethyl carbo- and heterocyclic structures.
Metathesis and Decomposition of Fischer Carbenes of Cyclometalated Z-Selective Ruthenium Metathesis Catalysts
Ahmed, Tonia S.,Grandner, Jessica M.,Taylor, Buck L. H.,Herbert, Myles B.,Houk,Grubbs, Robert H.
supporting information, p. 2212 - 2216 (2018/07/31)
The addition of vinyl ethers to Z-selective, cyclometalated ruthenium metathesis catalysts generates Fischer carbene complexes. Although Fischer carbenes are usually thought to be metathesis inactive, we show that Fischer carbenes are metathesis active under certain circumstances. These species were found to decompose facilely to Ru hydride complexes, as identified by both experiment and computation. Since vinyl ethers are often used to quench metathesis reactions implementing Ru-based metathesis catalysts, their decomposition to hydrides can have a deleterious effect on the desired stereochemistry of the olefin product.
From Resting State to the Steady State: Mechanistic Studies of Ene-Yne Metathesis Promoted by the Hoveyda Complex
Griffiths, Justin R.,Keister, Jerome B.,Diver, Steven T.
supporting information, p. 5380 - 5391 (2016/05/19)
The kinetics of intermolecular ene-yne metathesis (EYM) with the Hoveyda precatalyst (Ru1) has been studied. For 1-hexene metathesis with 2-benzoyloxy-3-butyne, the experimental rate law was determined to be first-order in 1-hexene (0.3-4 M), first-order in initial catalyst concentration, and zero-order for the terminal alkyne. At low catalyst concentrations (0.1 mM), the rate of precatalyst initiation was observed by UV-vis and the alkyne disappearance was observed by in situ FT-IR. Comparison of the rate of precatalyst initiation and the rate of EYM shows that a low, steady-state concentration of active catalyst is rapidly produced. Application of steady-state conditions to the carbene intermediates provided a rate treatment that fit the experimental rate law. Starting from a ruthenium alkylidene complex, competition between 2-isopropoxystyrene and 1-hexene gave a mixture of 2-isopropoxyarylidene and pentylidene species, which were trappable by the Buchner reaction. By varying the relative concentration of these alkenes, 2-isopropoxystyrene was found to be 80 times more effective than 1-hexene in production of their respective Ru complexes. Buchner-trapping of the initiation of Ru1 with excess 1-hexene after 50% loss of Ru1 gave 99% of the Buchner-trapping product derived from precatalyst Ru1. For the initiation process, this shows that there is an alkene-dependent loss of precatalyst Ru1, but this does not directly produce the active catalyst. A faster initiating precatalyst for alkene metathesis gave similar rates of EYM. Buchner-trapping of ene-yne metathesis failed to deliver any products derived from Buchner insertion, consistent with rapid decomposition of carbene intermediates under ene-yne conditions. An internal alkyne, 1,4-diacetoxy-2-butyne, was found to obey a different rate law. Finally, the second-order rate constant for ene-yne metathesis was compared to that previously determined by the Grubbs second-generation carbene complex: Ru1 was found to promote ene-yne metathesis 62 times faster at the same initial precatalyst concentration.
COMPOUNDS AND THE USE THEREOF IN METATHESIS REACTIONS
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Page/Page column 50, (2015/11/18)
The disclosure provides Group 6 complexes, which, in some embodiments, are useful for catalyzing olefin metathesis reactions. In some embodiments, the compounds are compounds of the following formula (I) wherein: M is a Group 6 metal atom; X is an oxygen
Synthesis and Reactivity of Homogeneous and Heterogeneous Ruthenium-Based Metathesis Catalysts Containing Electron-Withdrawing Ligands
Krause, Jens O.,Nuyken, Oskar,Wurst, Klaus,Buchmeiser, Michael R.
, p. 777 - 784 (2007/10/03)
The synthesis and heterogenization of new Grubbs-Hoveyda type metathesis catalysts by chlorine exchange is described. Substitution of one or two chlorine ligands with trifluoroacetate and trifluoromethanesulfonate was accomplished by reaction of [RuCl2(=CH-o-iPr-O-C6H 4)(IMesH2)] (IMesH2 = 1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene) with the silver salts CF3COOAg and CF3SO3Ag, respectively. The resulting compounds, [Ru(CF3SO3) 2(=CH-o-iPr-O-C6H4)(IMesH2)] (1), [RuCl(CF3SO3)(=CH-o-iPr-O-C6H 4)(IMesH2)] (2), and [Ru(CF3CO 2)2(=CH-o-iPr-O-C6H4)(IMesH 2)] (3) were found to be highly active catalysts for ring-closing metathesis (RCM) at elevated temperature (45°C), exceeding known ruthenium-based catalysts in catalytic activity. Turn-over numbers (TONs) up to 1800 were achieved in RCM. Excellent yields were also achieved in enyne metathesis and ring-opening cross metathesis using norborn-5-ene and 7-oxanorborn-5-ene-derivatives. Even more important, 3 was found to be highly active in RCM at room temperature (20°C), allowing TONs up to 1400. Heterogeneous catalysts were synthesized by immobilizing [RuCl2(= CH-o-iPr-O-C6H4)(IMesH2)] on a perfluoroglutaric acid derivatized polystyrene-divinylbenzene (PS-DVB) support (silver form). The resulting supported catalyst [RuCl(polymer-CH 2-O-CO-CF2-CF2-CF 2-COO)(=CH-o-iPr-O-C6H4)(IMesH2)] (5) showed significantly reduced activities in RCM (TONs = 380) compared with the heterogeneous analogue of 3. The immobilized catalyst, [Ru(polymer-CH 2-O-CO-CF2-CF2-CF2-COO)(CF 3CO2)(=CH-o-iPr-O-C6H4)(IMesH 2)] (4) was obtained by substitution of both Cl ligands of the parent Grubbs-Hoveyda catalyst by addition of CF3COOAg to 5. Compound 4 can be prepared in high loadings (160 mg catalyst g-1 PS-DVB) and possesses excellent activity in RCM with TONs up to 1100 in stirred-batch RCM experiments. Leaching of ruthenium into the reaction mixture was unprecedentedly low, resulting in a ruthenium content -1) in the final RCM-derived products.
