36508-31-3Relevant academic research and scientific papers
A Highly Efficient Synthesis of Z-Macrocycles Using Stereoretentive, Ruthenium-Based Metathesis Catalysts
Ahmed, Tonia S.,Grubbs, Robert H.
, p. 11213 - 11216 (2017)
A highly efficient, Z-selective ring-closing metathesis system for the formation of macrocycles using a stereoretentive, ruthenium-based catalyst supported by a dithiolate ligand is reported. The catalyst is remarkably active as observed in initiation experiments showing complete catalyst initiation at ?20 °C within 10 minutes. Macrocyclization reactions generated Z-products from easily accessible diene starting materials bearing a Z-olefin moiety. This approach provides a more efficient and selective route to Z-macrocycles relative to previously reported systems. Reactions were completed within shorter reaction times, and turnover numbers of up to 100 could be achieved. Macrocyclic lactones ranging in size from twelve- to seventeen-membered rings were synthesized in moderate to high yields (67–79 %) with excellent Z-selectivity (95–99 %).
REACTIONS OF OLEFIN DERIVATIVES IN THE PRESENCE OF METATHESIS CATALYSTS
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Paragraph 000169, (2019/09/04)
The invention provides a method for synthesizing musk macrocycles comprising contacting an easily accessible diene starting materials bearing a Z-olefin moiety and performing a ring closing metathesis reaction in the presence of a Group 8 olefin metathesi
A HIGHLY EFFICIENT SYNTHESIS OF Z-MACROCYCLES USING STEREORETENTIVE, RUTHENIUM-BASED METATHESIS CATALYSTS
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, (2018/12/02)
A highly efficient, Z-selective ring-closing metathesis system for the formation of macrocycles using a stereoretentive, ruthenium-based catalyst supported by a dithiolate ligand is reported. This catalyst is demonstrated to be remarkably active as observed in initiation experiments showing complete catalyst initiation at - 20°C within 10 min. Using easily accessible diene starting materials bearing a Z-olefin moiety, macrocyclization reactions generated products with significantly higher Z-selectivity in appreciably shorter reaction times, in higher yield, and with much lower catalyst loadings than in previously reported systems. Macrocyclic lactones ranging in size from twelve-mem bered to seventeen-membered rings are synthesized in moderate to high yields (68 - 79% yield) with excellent Z-selectivity (95% - 99% Z).
A General Decomposition Pathway for Phosphine-Stabilized Metathesis Catalysts: Lewis Donors Accelerate Methylidene Abstraction
McClennan, William L.,Rufh, Stephanie A.,Lummiss, Justin A. M.,Fogg, Deryn E.
, p. 14668 - 14677 (2016/11/18)
Sterically accessible Lewis donors are shown to accelerate decomposition during catalysis, for a broad range of Grubbs-class metathesis catalysts. These include benzylidene derivatives RuCl2(NHC)(PCy3)(=CHPh) (Ru-2: NHC = H2IMes, a; IMes, b; H2IPr, c; IPr, d; H2ITol, e) and indenylidene complexes RuCl2(NHC)(PCy3)(=C15H10) (NHC = H2IMes, Ru-2f; IMes, Ru-2g). All of these precatalysts form methylidene complex RuCl2(NHC)(=CH2) Ru-3 as the active species in metathesis of terminal olefins, and generate RuCl2(NHC)(PCy3)(=CH2) Ru-4 as the catalyst resting state. On treatment with a 10-fold excess of pyridine, Ru-4a and Ru-4b decomposed within minutes in solution at RT, eliminating [MePCy3]Cl A by net loss of three ligands (PCy3, methylidene, and one chloride), and a mesityl proton. In comparison, loss of A from Ru-4a in the absence of a donor requires up to 3 days at 55 °C. The σ-alkyl intermediate RuCl2(13CH2PCy3)(NHC) (py)2 resulting from nucleophilic attack of free PCy3 on the methylidene ligand was undetectable for the H2IMes system, but was spectroscopically observable for the IMes system. The relevance of this pathway to decomposition of catalysts Ru-2a-g was demonstrated by assessing the impact of pyridine on the in situ-generated methylidene species. Slow initiation (as observed for the indenylidene catalysts) did not protect against methylidene abstraction. Importantly, studies with Ru-4a and Ru-4b indicated that weaker donors (THF, MeCN, DMSO, MeOH, and even H2O) likewise promote this pathway, at rates that increase with donor concentration, and severely degrade catalyst productivity in RCM, even for a readily cyclized substrate. In all cases, A was the sole or major 31P-containing decomposition product. For DMSO, a first-order dependence of decomposition rates on DMSO concentration was established. This behavior sends a warning about the use of phosphine-stabilized metathesis catalysts in donor solvents, or with substrates bearing readily accessible donor sites. Addition of pyridine to RuCl2(H2IMes)(PCy3)(=CHMe) did not result in ethylidene abstraction, indicating that this decomposition pathway can be inhibited by use of substrates in which the olefin bears a β-methyl group.
