5309-50-2Relevant academic research and scientific papers
Conformational Control of Initiation Rate in Hoveyda-Grubbs Precatalysts
Gregg, Zackary R.,Griffiths, Justin R.,Diver, Steven T.
supporting information, p. 1526 - 1533 (2018/06/04)
When the coordinating isopropyl ether of the Hoveyda precatalyst is replaced by a cyclohexyl ether, it is possible to control the substituent's conformation in either the equatorial or axial position. A stereodivergent synthesis of axial and equatorial cyclohexyl vinyl ethers provided access to new ruthenium metathesis precatalysts by carbene exchange. The conformational disposition of the coordinating aryl ether was found to have a significant effect on the reactivity of the precatalyst in alkene metathesis. The synthesis of four new Ru carbene complexes is reported, featuring either the 1,3-bis(2,4,6-trimethylphenyl)dihydroimidazolylidene (H2IMes) or the 1,3-bis(2,6-diisopropylphenyl)dihydroimidazolylidene (SIPr) N-heterocyclic carbene ligand. The conformational isomers in the SIPr series were structurally characterized. Performance testing of all new precatalysts in three different ring-closing metatheses and an alkene cross metathesis illustrated superior performance by the precatalysts bearing axial coordinating ethers. Initiation rates with butyl vinyl ether were also measured, providing a useful comparison to existing Hoveyda-type metathesis precatalysts. Use of conformational control of the coordinating ether substituent provides a new way to modulate reactivity in this important class of alkene metathesis precatalysts.
Kinetic benchmarking reveals the competence of prenyl groups in ring-closing metathesis
Bahou, Karim A.,Braddock, D. Christopher,Meye, Adam G.,Savage, G. Paul
supporting information, p. 5332 - 5335 (2017/11/07)
A series of prenyl-containing malonates are kinetically benchmarked against the standard allyl-containing congeners using a ruthenium benzylidene precatalyst for ringclosing metatheses. The prenyl grouping is found to be a superior acceptor olefin compared to an allyl group in RCM processes with ruthenium alkylidenes derived from terminal alkenes. The prenyl group is also found to be a highly competent acceptor for a ruthenium alkylidene derived from a 1, 1-disubstituted olefin in a RCM process.
Highly Activated Second-Generation Grubbs-Hoveyda Catalyst Driven by Intramolecular Steric Strain
Kobayashi, Yuki,Miyazaki, Hiroki,Inukai, Sae,Takagi, Chika,Makino, Reo,Shimowaki, Kento,Igarashi, Rina,Sugiyama, Yuya,Nakamura, Shuichi,Matsugi, Masato
supporting information, p. 2352 - 2356 (2016/09/28)
Various Grubbs-Hoveyda second-generation catalysts activated by intramolecular steric strain were prepared. The variant bearing a 9-anthracenyl group in the ligand moiety exhibited the highest catalytic activity. The new anthracenyl-type-activated catalyst was used in a ring-closing metathesis reaction to effectively provide a 4-substituted product effectively.
A medium fluorous Grubbs-Hoveyda 2nd generation catalyst for phase transfer catalysis of ring closing metathesis reactions
Kobayashi, Yuki,Inukai, Sae,Kondo, Natsuki,Watanabe, Tomoko,Sugiyama, Yuya,Hamamoto, Hiromi,Shioiri, Takayuki,Matsugi, Masato
supporting information, p. 1363 - 1366 (2015/03/04)
A fluorous Grubbs-Hoveyda metathesis catalyst supported on Teflon powder, that readily moves between the solid phase (Teflon) and the liquid phase (DMF) was prepared. By modulating the hydrophobicity of the reaction medium at the end of the reaction, the supported catalyst could be recovered by simple filtration even though the catalyst existed in a homogeneous state during the reaction. In RCM reactions, the catalyst could be reused up to three times with only a slight loss in reactivity with each subsequent cycle.
Removal of ruthenium using a silica gel supported reagent
French, Jonathan M.,Caras, Caley A.,Diver, Steven T.
supporting information, p. 5416 - 5419 (2013/11/19)
A solid-supported isocyanide ligand was developed to destroy active metathesis catalysts and to remove ruthenium byproducts from metathesis reactions. This method was able to significantly reduce the concentration of residual ruthenium from the organic products of several alkene and ene-yne metathesis reactions, under a variety of different conditions.
Study on the total synthesis of velbanamine: Chemoselective dioxygenation of alkenes with PIFA via a stop-and-flow strategy
Liu, Huili,Zheng, Kuan,Lu, Xiang,Wang, Xiaoxia,Hong, Ran
supporting information, p. 983 - 990 (2013/07/19)
A "stop-and-flow" strategy was developed for the chemoselective dioxygenation of alkenes with a PIFA-initiated cyclization. This method is conceived for the desymmetrization of seco-diene, and a series of substituted 5-hydroxymethyl-γ-lactones were constructed after hydrolysis. This strategy also differentiates terminally substituted alkenes and constitutes a potentially novel synthetic approach for the efficient synthesis toward velbanamine.
Non-Cp titanium alkoxide-based homolytic ring-opening of epoxides by an intramolecular hydrogen abstraction in β-titanoxy radical intermediates
Kawaji, Tsuyoshi,Shohji, Noriaki,Miyashita, Kenji,Okamoto, Sentaro
supporting information; experimental part, p. 7857 - 7859 (2011/09/15)
A low-valent titanium species derived in situ from Ti(O-i-Pr)4, Me3SiCl and Mg powder in tetrahydrofuran reacted with epoxides to selectively provide less hindered alcohols via a homolytic ring-opening of epoxides, in which the intermediate β-titanoxy radical intramolecularly abstracted a hydrogen atom from an alkoxy moiety in the titanium complexes.
Ring-closing olefin metathesis in the aqueous phase of amphiphilic conetworks consisting of fluorophilic and hydrophilic compartments
Hensle, Eva M.,Tobis, Jan,Tiller, J?rg C.,Bannwarth, Willi
experimental part, p. 968 - 973 (2009/04/04)
A Grubbs-Hoveyda-Type metathesis catalyst bearing a tris(perfluoroalkyl)silyl tag was immobilized in the fluorophilic phase of amphiphilic conetworks (APCNs). This catalytic system was applied to ring-closing metathesis (RCM) reactions in aqueous media. Different substrates were evaluated and with 10 mol% of catalyst at 60 °C good conversions were observed. Reuse of the catalytic system was possible, but resulted generally in lower conversions.
Catalytic deallylation of allyl- and diallylmalonates
Necas, David,Tursky, Matyas,Kotora, Martin
, p. 10222 - 10223 (2007/10/03)
Substituted allylmalonates undergo the selective C-C bond cleavage in the presence of triethylaluminum and a catalytic amount of nickel and ruthenium phosphine complexes, resulting in the loss of the allyl moiety and formation of monosubstituted malonates. Comparison of reactivity of the nickel and ruthenium complexes showed that the use of the former is general with respect to the structure of the substituted allylmalonates, and the activity of the latter depended on the substitution pattern of the double bond of the allylic moiety. The smooth deallylation may encourage the use of the allyl group as a protective group for the acidic hydrogen in malonates. Copyright
Effects of Olefin Substitution on the Ring-Closing Metathesis of Dienes
Kirkland, Thomas A.,Grubbs, Robert H.
, p. 7310 - 7318 (2007/10/03)
Ruthenium alkylidene 1 and molybdenum alkylidene 2 have been utilized in the ring-closing metathesis (RCM) of dienes containing gem-disubstituted olefins to yield tri- and tetrasubstituted cyclic olefins. Dienes with sterically demanding and/or electron-withdrawing substituents such as Ph, CO2Me, and tBu were cyclized successfully with 2, but did not cyclize with 1. Tetrasubstituted cyclic olefins could be formed with 2, but not using alkylidene 1. Dienes with allylic functional groups yielded functionalized cyclic olefins when treated with 1.
