Kinetic Selectivity of Olefin Metathesis Catalysts Bearing Cyclic (Alkyl)(Amino)Carbenes

Anderson, Donde R.; Ung, Thay; Mkrtumyan, Garik; Bertrand, Guy; Grubbs, Robert H.; Schrodi, Yann

doi:10.1021/om7008028

Cited by 140 publications

(127 citation statements)

References 15 publications

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“…These results showed that (8) and (9) are less selective toward ethenolysis than their first generation equivalents (6) and (7) as consistently reported. First generation catalysts give ethenolysis reaction mixtures that correspond to kinetic product distributions with a selectivity toward ethenolysis products, while second generation catalysts are not kinetically selective but tend to yield reaction mixtures that are closer to thermodynamic product distributions [4,10]. It has been well documented that second generation NHC-based catalysts have better stability and activity toward general metathesis reactions [14].…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, it became critical to develop more efficient and selective olefin metathesis catalysts for the commercial use of ethenolysis. Recently, we have reported 35 000 TONs, the highest recorded to date, with newly developed catalyst (21) in collaboration with Grubbs and coworkers [10]. For manufacturing of commodity chemicals, the TON should be at least 50 000 [4].…”

Section: Introductionmentioning

confidence: 98%

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Ruthenium Olefin Metathesis Catalysts for the Ethenolysis of Renewable Feedstocks

Schrodi¹,

Ung²,

Vargas³

et al. 2008

CLEAN Soil Air Water

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Communication Ruthenium Olefin Metathesis Catalysts for the Ethenolysis of Renewable FeedstocksRuthenium olefin metathesis catalysts have been evaluated for the ethenolysis of methyl oleate, a natural seed oil derivative, to produce useful terminal olefins. Several N-heterocyclic carbene-based ruthenium catalysts demonstrate good activity and selectivity for the formation of terminal olefins. In particular, catalysts (10) and (21) achieved higher TONs (A20 000).

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Ruthenium Olefin Metathesis Catalysts for the Ethenolysis of Renewable Feedstocks

Schrodi¹,

Ung²,

Vargas³

et al. 2008

CLEAN Soil Air Water

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“…53,54 The carbene ruthenium complexes 67-69 ( Figure 5.17 The kinetic selectivity of the CAAC-based catalysts was investigated by probing the E/Z diastereoselectivity in the cross metathesis of cis-1,4-diaceto-2-butene with allylbenzene (equation 5.5). 55 Compared to the commercially available Grubbs' catalysts, 67-69 afforded lower E/Z ratios (3:1 at 70% conversion, ~ 2:1 at < 60% conversion). The activity of 69 is significantly higher than that of the more sterically hindered catalysts 67 and 68.…”

Section: Olefin Metathesismentioning

confidence: 97%

Non-classical N-Heterocyclic Carbene Complexes

Krüger

Albrecht²

2010

N-Heterocyclic Carbenes

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The expansion of the concept of N-heterocyclic carbenes as ligands for transition metals to mesoionic ligand systems has led to the discovery of a wide range of non-classical carbenetype ligands. These non-classical carbene-type ligands are characterised by a significantly lower heteroatom stabilisation of the (putative) free carbene, a situation that also affects the ligand donor properties and hence the reactivity of the coordinated metal centre. Based on the unique impact of non-classical carbene-type ligands, a number of attractive transition metal-catalysed processes have been disclosed in recent years, predominantly in the area of cross-coupling reactions, hydrogenations, and olefin metathesis. IntroductionThe transition metal chemistry of N-heterocyclic carbenes is dominated by 2-imidazolylidenes and their derivatives including oxazoles, thiazoles, 1,2,4-triazoles, and pyrimidines, as well as related saturated systems. Despite these formal ambiguities, non-classical variations of NHCs constitute an attractive class of ligands with great opportunities for catalysis and synthesis in general. This chapter aims to overview the most recent advances in using non-classical NHC ligands in transition metal-mediated catalysis and to illustrate the attractive prospects that emerge from these achievements. Synthesis of Non-Classical Carbene ComplexesA variety of different methods have been used for the formation of classical NHC complexes, and most of these methods are also applicable to the synthesis of non-classical NHC metal systems. Most frequently used methods for metallating cyclic non-classical carbene precursors include direct metallation via C-H bond activation, and C-X bond 13 as well as C-H bond oxidative addition. 14 Less common are transmetallation protocols, first because the relevant metal carbene precursors, especially the Ag-carbene salts, have only limited stability. 15 In addition, argentation suffers from a low regioselectivity, partially originating from the weak acidity of the proton to be removed. For example, exocyclic C-H bond activation has been observed in C2-methylated imidazolium salts, a reaction pathway that is successfully prevented when using C2-arylated imidazolium salts. 16Another key route towards metal carbene complexes involves the generation of the free carbene, either in situ or isolated, and subsequent metal coordination. While the stability of classical carbenes makes the free carbene route the method of choice for complex synthesis (and largely contributed to the enormous success of this class of ligands), the reduced heteroatom stabilisation in non-classical carbenes generally precludes the formation of free carbenes. 17 Theoretical investigations using energy decomposition analyses have shown that for example 4-imidazolylidene is about 20 kcal mol -1 less stable than its classical counterpart, 2-imidazolylidene. 18While free carbenes with low heteroatom stabilisation such as 1 (Figure 5. 2) 7Interestingly, abnormal imidazol-4-ylidene complexes have also been o...

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“…以 cis-1,4-二乙酰氧基-2-丁烯 32 与烯丙基苯 33 的交叉复分解(crossing metathesis, 简称 CM)反应(Eq. 5)为例 [34] , Grubbs 二代催化剂 3 和 25 主要生成热力学稳定的 E 构型烯烃 34 [33] , 而 22, 23 和 24 对 Z 构型烯烃产物 35 的选择性明显高于 3 和 25; 另一方面, 24 的活性仍比 22 和 23 的活性高很多, 这说明高的 Z 构型烯烃选择性与催化剂的活性关系不大, 这很可能是 CAACs 配体固有的属性 [34] . 再以油酸甲酯 36 的乙烯分解反应为例(Eq.…”

Section: Caacs 配体在烯烃复分解催化剂中的研究现状unclassified

“…再以油酸甲酯 36 的乙烯分解反应为例(Eq. 6) [34] , Grubbs 二代催化剂 3 和 25 对端烯 37 和 38 的选择性也较差(分别为 44% 和 33%) [33] 不可忽视的作用, 不同的膦配体带来的的催化效果也不同 [36] . …”

Section: Caacs 配体在烯烃复分解催化剂中的研究现状unclassified

Cyclic(alkyl)(amino)carbenes and the Research Prospect in Olefin Metathesis Reaction

蔡援¹,

开铖²,

黄毅勇³

et al. 2014

Chin. J. Org. Chem.

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Olefin metathesis has been one of the most important methods to construct carbon-carbon double bonds, which has been enabled by development of well-defined transition-metal catalysts (e.g. [L 2 X 2 Ru＝CHR], L＝PCy 3 ). A significant gain to increase the catalyst stability and activity was achieved after replacing a single PCy 3 ligand of L 2 X 2 Ru＝CHR (L＝PCy 3 ) with cyclic biamino cabene, such as 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene (H 2 IMes). In 2005, Bertrand et al. discovered a novel ligand-yclic(alkyl)(amino)cabene (CAAC), which displayed more electron donating and more electrophilic in comparison with cyclic diamino cabene. It is logic that more electronegative amino group is replaced by alkyl group in CAAC. Furthermore, a quaternary carbon at the α position of carbene center of CAAC may make a big difference from cyclic diamino cabene, which can change the steric environment of CAAC easily and creat a chiral center next to the carbene. In this research prospect, synthesis, property and application of CAACs in olefin metathesis catalysis are introduced. Finally, the issues remained in this research area are summarized and an outlook for the development in the future is given.

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Kinetic Selectivity of Olefin Metathesis Catalysts Bearing Cyclic (Alkyl)(Amino)Carbenes

Cited by 140 publications

References 15 publications

Ruthenium Olefin Metathesis Catalysts for the Ethenolysis of Renewable Feedstocks

Ruthenium Olefin Metathesis Catalysts for the Ethenolysis of Renewable Feedstocks

Non-classical N-Heterocyclic Carbene Complexes

Cyclic(alkyl)(amino)carbenes and the Research Prospect in Olefin Metathesis Reaction

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