Chemodivergent Metathesis of Dienynes Catalyzed by Ruthenium–Indenylidene Complexes: An Experimental and Computational Study

Clavier, Hervé; Correa, Andrea; Escudero‐Adán, Eduardo C.; Benet‐Buchholz, Jordi; Cavallo, Luigi; Nolan, Steven P.

doi:10.1002/chem.200900976

Cited by 62 publications

(38 citation statements)

References 121 publications

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“…These distances are about 0.30 shorter than those computed for olefin complexes 2E (Scheme 5) and suggest a stronger local interaction between the alkyne and the metal centre, in agreement with previous results of Lippstreu and Straub [24] and Cavallo et al [21] The transition structure of the alkyne coordination was located for the precatalyst activation process and the propagating alkylidene interconversion. In both cases, the incoming alkyne is still far from the metal centre.…”

Section: Wwwchemeurjorgsupporting

confidence: 88%

“…The Ru···C ene distance varies between 3.08 and 3.23 . To our knowledge, this transition structure has never been reported before by any of the already published computational studies on Ru-based enyne metathesis [21,24,25] or simply alkene metathesis. [22,42] This is probably because the potentialScheme 3.…”

Section: Resultsmentioning

confidence: 72%

“…[6,[17][18][19]21] This catalytic process is even more complex, since two different pathways can be distinguished for the yne-then-ene mechanism depending on the substrate orientation, that is, the exo (Scheme 2 b) and the endo (Scheme 2 c) approaches, which in general lead to different products. [6,9,17,18] However, even if formation of the endo product seems plausible, it is usually not observed when an Ru-based catalyst is used, or it is only observed in minor amounts.…”

Section: Introductionmentioning

confidence: 98%

“…[6,17,18,20] In fact, to our knowledge the number of examples in which the endo product is the major one is very small. [18] Many theoretical studies have dealt with Ru-based metathesis reactions [22,23] but, to our knowledge, only three studies have considered the enyne case [21,24,25] and only two [21,24] of them the intramolecular process. They agree that, although alkyne coordination to the metal is preferred, enethen-yne seems to be the most favourable pathway.…”

Section: Introductionmentioning

confidence: 99%

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Mechanistic Insights into Ring‐Closing Enyne Metathesis with the Second‐Generation Grubbs–Hoveyda Catalyst: A DFT Study

Núñez‐Zarur

Solans‐Monfort

Rodrı́guez-Santiago

et al. 2011

Chemistry A European J

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The full catalytic process (precatalyst activation, propagating cycle and active-species interconversion) of the ring-closing enyne metathesis (RCEYM) reaction of 1-allyloxy-2-propyne with the Grubbs-Hoveyda complex as catalyst was studied by B3LYP density functional theory. Both the ene-then-yne and yne-then-ene pathways are considered and, for the productive catalytic cycle, the feasibility of the endo-yne-then-ene route is also explored. Calculations predict that the ene-then-yne and yne-then-ene pathways proceed through equivalent steps, the only major difference being the order in which they take place. In this way, all alkene metathesis processes studied here involve four steps: olefin coordination, cycloaddition, cycloreversion and olefin decoordination. Among them, the two more energetically demanding ones are the olefin coordination and decoordination steps. The reaction of the alkyne fragment consists of two steps: alkyne coordination and alkyne skeletal reorganization, the latter of which has the highest Gibbs energy barrier. Comparison between the ene-then-yne and yne-then-ene pathways shows that there is no clear energetic preference for either of the two processes, and thus both should be operative when unsubstituted enynes are involved. In addition, although the endo orientation is computed to be slightly disfavored, it is not ruled out for 1-allyloxy-2-propyne, and thus calculations seem to indicate that the exo versus endo selectivity is strongly influenced by the presence of substituents in the reagent.

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Section: Wwwchemeurjorgsupporting

confidence: 88%

Section: Resultsmentioning

confidence: 72%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Mechanistic Insights into Ring‐Closing Enyne Metathesis with the Second‐Generation Grubbs–Hoveyda Catalyst: A DFT Study

Núñez‐Zarur

Solans‐Monfort

Rodrı́guez-Santiago

et al. 2011

Chemistry A European J

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“…[7] For RCM involving phosphine catalysts, for example, 3 a, and terminal enynes, computational investigations [7,8] and isotopic labelling experiments [3] support earlier proposals [5b, 9] that ethylene acts as an alkene surrogate for the enyne (1) in the release of product (2) through alkene-alkylidene exchange with intermediate 5.…”

supporting

confidence: 57%

A Simple and Effective Co‐Catalyst for Ring‐Closing Enyne Metathesis Using Grubbs I type Catalysts: A Practical Alternative to “Mori’s Conditions”

Lloyd‐Jones

Robinson

Lefort

et al. 2010

Chemistry A European J

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In 1998 Mori reported [1] that ethylene improved turnover in the ring-closing metathesis (RCM) of enynes (1!2), [2] employing Grubbs generation I catalyst (3 a); for example, low yields of 2 a-c under 1 atm argon, became near-quantitative (99 %) under 1 atm. ethylene.[1] Subsequent kinetic analysis [3] revealed that ethylene not only increases the turnover frequency, but also reduces the impact of catalyst deactivation processes. The beneficial effect of ethylene is observed with many enyne substrates, particularly those with terminal alkyne moieties, and unsurprisingly, "Moris conditions" have been widely adopted (Scheme 1). [4] Two basic mechanisms have been proposed for the RCM of enynes involving intermolecular [5] metal-alkylidene propagation. These mechanisms are often referred to as the "yne-then-ene" and "ene-then-yne" pathways.[2] Evidence for both pathways has been presented, and phosphine catalysts, for example, 3 a, [6] appear to favour the "ene-then-yne" pathway (cycle A, Scheme 2). [7] For RCM involving phosphine catalysts, for example, 3 a, and terminal enynes, computational investigations [7,8] and isotopic labelling experiments [3] support earlier proposals [5b, 9] that ethylene acts as an alkene surrogate for the enyne (1) in the release of product (2) through alkene-alkylidene exchange with intermediate 5.[10] A second alkene-alkylidene exchange of 6 (R = H) with 1, to generate 4, connects the secondary cycle B with primary cycle A, [11] liberating the ethylene (R = H), which thus acts as a co-catalyst.During our earlier study of "Moris conditions" [3] we noted that co-reaction of the about threefold-faster-reacting substrate 1 c with 1 a resulted in a small but noticeable decrease in the rate of RCM of 1 a. This suggested to us that an appropriately "tuned" alk-1-ene might be able to act as an efficient co-catalyst, in a manner analogous to ethylene. Herein we report on a kinetic and isotopic labelling investigation into this concept, and the development of a simple alkene co-catalyst that provides practical advantage to "Moris conditions" for the RCM of terminal enynes using Grubbs I catalyst (3 a). Scheme 2. The "ene-then-yne" cycle (A) for RCM of enynes 1!2 and secondary cycle B to account for acceleration under "Moris conditions" in which R = H.

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Ruthenium‐Carbene Complexes

Ho¹,

Fieser²,

Fieser³

2011

Fieser and Fieser's Reagents for Organic Synthesis

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Chemodivergent Metathesis of Dienynes Catalyzed by Ruthenium–Indenylidene Complexes: An Experimental and Computational Study

Cited by 62 publications

References 121 publications

Mechanistic Insights into Ring‐Closing Enyne Metathesis with the Second‐Generation Grubbs–Hoveyda Catalyst: A DFT Study

Mechanistic Insights into Ring‐Closing Enyne Metathesis with the Second‐Generation Grubbs–Hoveyda Catalyst: A DFT Study

A Simple and Effective Co‐Catalyst for Ring‐Closing Enyne Metathesis Using Grubbs I type Catalysts: A Practical Alternative to “Mori’s Conditions”

Ruthenium‐Carbene Complexes

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