Olefin Metathesis Reactions

Harutyunyan, Syuzanna R.; Michrowska, Anna; Grela, Karol; Connon, Stephen J.; Dunne, Aideen M.; Blechert, Siegfried; Bhaskar, G.; Rao, B. Venkateswara

doi:10.1002/0470862017.ch9

Cited by 9 publications

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“…At the same time, the rates of their isomerization are reversed 1a is completely transformed into 1b within a few days, while 2a has a similar half-life. These apparent discrepancies can be rationalized in terms of the influence of electronic effects of a donor atom on the chelate stability, the phenomena previously applied by us for activation of the Hoveyda catalyst I . , To compare the properties of quinoline and quinoxaline ligands in more detail, we calculated , the structures of 8-vinylquinoline and 5-vinylquinoxaline (precursors of the carbene ligands of 1a and 2a ) and studied their geometries and electron distribution (viewed as EPS charges located at the chelating nitrogen atoms; Figure ) 10 Structures of 8-vinylquinoline (left) and 5-vinylquinoxaline (right) optimized 25,26 with B3LYP/6-31** and their electron density cubes mapped with ESP 29 (electostatic potential charge values at chelating nitrogen atoms: for quinoline, −0.410; for quinoxaline, −0.197).…”

Section: Discussionmentioning

confidence: 99%

“…The Ru−O chelate can easily dissociate and release active 14-electron ruthenium complexes, the intrinsic catalytic intermediates . Catalyst I was later successfully fine-tuned in order to increase its activity and applicability by the introduction of electron-withdrawing groups to diminish the donor properties of the oxygen atom. , Otherwise, oxygen carbonyl donors, e.g. 2-vinylbenzoic acid derivatives ( II ; L = PCy 3 , 1,3-dimesitylimidazol-2-ylidene), are less reactive in the RCM of substituted dienes .…”

Section: Introductionmentioning

confidence: 99%

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Structure and Activity Peculiarities of Ruthenium Quinoline and Quinoxaline Complexes: Novel Metathesis Catalysts

et al. 2006

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Novel metathesis catalysts that are derivatives of 8-vinylquinoline, (H 2 IMes)(Cl) 2 Ru(CH-κ 2 (C,N)-8-C 9 H 6 N) (1a; H 2 IMes ) 1,3-dimesityl-4,5-dihydroimidzol-2-ylidene), and 5-vinylquinoxaline, (H 2 IMes)-(Cl) 2 Ru(CH-κ 2 (C,N)-5-C 8 H 5 N 2 ) (2a), which possess five-membered chelate rings, were synthesized in ligand exchange reactions with (H 2 IMes)(PCy 3 )(Cl) 2 RudCHPh. Both 1a and 2a are formed as complexes with the trans-dichloro geometry common for Grubbs-type complexes, while on prolonged storage in dichloromethane they isomerize to the thermodynamically favored cis-dichloro isomers (1b and 2b, respectively). The structures of compounds 1a,b were confirmed by X-ray analysis. The kinetics of trans to cis isomerization were measured by 1 H NMR to give the rate constants k 1af1b ) 3.2 × 10 -2 h -1 and k 2af2b ) 5.5 × 10 -3 h -1 in dichloromethane-d 2 at 23 °C. Investigations of the relative activities of these catalysts in model RCM and enyne reactions showed that catalyst 1a was faster than 1b (and 2a faster than 2b) but that 2a was faster than 1a.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Structure and Activity Peculiarities of Ruthenium Quinoline and Quinoxaline Complexes: Novel Metathesis Catalysts

et al. 2006

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“… 3 ), ester 4b–4d (ref. 3 , 6 , 11 and 12 ) and amide 4e (ref. 6 ) functionalities, have been made ( Table 1 , entries 4–8).…”

Section: Introductionmentioning

confidence: 99%

“… 3 , 6 , 11 and 12 ) and amide 4e (ref. 6 ) functionalities, have been made ( Table 1 , entries 4–8). Most of these complexes, which have been verified by X-ray single crystal, shows an extra coordination with the carbonyl oxygen which result in an additional protection of the metal site, and hence, exhibiting a higher activity and stability than those achieved earlier.…”

Section: Introductionmentioning

confidence: 99%

Highly efficient Ru(ii)–alkylidene based Hoveyda–Grubbs catalysts for ring-closing metathesis reactions

et al. 2021

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“…The original modifications made in Warsaw consisted of the introduction of certain electron-withdrawing substituents, such as NO 2 , on the aromatic ring in a para position relative to the isopropoxy unit, with the aim of labilizing the bonding interaction between the oxygen of the ether function and the metal. Such a strategy proved to be valuable, giving in particular our very efficient “nitro-Hoveyda” catalyst N2 shown in Chart , exhibiting a high initiation rate and a broad application scope . In this context, recent DFT calculations have led to the proposal that both the enhanced activity of this catalyst and its recovery are dependent on the π delocalization between the phenyl and the carbene …”

Section: Introductionmentioning

confidence: 99%

Rational Design and Evaluation of Upgraded Grubbs/Hoveyda Olefin Metathesis Catalysts: Polyfunctional Benzylidene Ethers on the Test Bench

et al. 2011

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The series of upgraded Grubbs/Hoveyda second-generation catalysts (H2IMes)(Cl)2RuC(H)(C6H4OR) (E2 (71% yield), R = CH(Me)(C(O)OMe); M2 (58% yield), R = CH(C(O)OMe)2; Kme2 (88% yield), R = CH2C(O)Me; Ket2 (63% yield), R = CH2C(O)Et); C2 (58% yield), R = C(Me)CN) were prepared by the reaction of the Grubbs second-generation catalyst (H2IMes)(Cl)2Ru(CHPh)(PCy3) (G2) with the appropriate ortho-substituted ether H(Me)CCHC6H4OR in the presence of CuCl as a phosphine scavenger. The X-ray structures of these complexes reveal that the terminal oxygen of the ester, ketone, or malonate group installed as the terminal substituent of the benzylidene ether is coordinated to the metal, giving an octahedral structure. In contrast, the nitrile group of the complex C2 remains uncoordinated. Even more sophisticated complexes, incorporating both a coordinating group R (ester or ketone) as a terminal substituent of the ether and an electron-withdrawing group X (NO2 or C(O)Me) on the aromatic ring, were synthesized: (H2IMes)(Cl)2RuC(H)[(C6H3X)OR] (NE2 (69% yield), R = CH(Me)(C(O)OMe), X = NO2; KE2 (57% yield), R = CH(Me)(C(O)OMe), X = C(O)Me; KK2 (56% yield), R = CH2C(O)Me, X = C(O)Me). All these complexes were used as catalyst precursors in standard metathesis reactions and compared with commercial catalysts such as Grubbs II (G2), Grubbs/Hoveyda II (H2), and Nitro catalyst (N2). The catalysts NE2, KE2, N2, and M2 exhibit excellent performances in the RCM of diallyl malonate or the RCM of diallyltosylamide at 0 °C. The catalysts M2, N2, and Kme2 are also very efficient for the RCM of allyl methallyl malonate to yield a trisubstituted olefin. The same complexes are also active for cross-metathesis, and several low-loading tests are also presented. Finally, a very challenging example of the synthesis of BILN 2061 (hepatitis C virus HCV NS3 protease inhibitor having antiviral effect in infected humans) is presented, where the best performances are recorded with E2 (95% conversion) and N2 (93% conversion). The enhanced activity of the reported complexes is understood in terms of their enhanced stability and their ability to liberate progressively and continuously the active species in solution.

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Olefin Metathesis Reactions

Cited by 9 publications

References 0 publications

Structure and Activity Peculiarities of Ruthenium Quinoline and Quinoxaline Complexes: Novel Metathesis Catalysts

Structure and Activity Peculiarities of Ruthenium Quinoline and Quinoxaline Complexes: Novel Metathesis Catalysts

Highly efficient Ru(ii)–alkylidene based Hoveyda–Grubbs catalysts for ring-closing metathesis reactions

Rational Design and Evaluation of Upgraded Grubbs/Hoveyda Olefin Metathesis Catalysts: Polyfunctional Benzylidene Ethers on the Test Bench

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