Probing the Mechanism of the Baylis–Hillman Reaction by Electrospray Ionization Mass and Tandem Mass Spectrometry

Santos, Leonardo S.; Pavam, Cesar Henrique; Almeida, Wanda P.; Coelho, Fernando; Eberlin, Marcos N.

doi:10.1002/ange.200460059

Cited by 84 publications

(40 citation statements)

References 56 publications

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“…[3] In principle, they make the detection and study not only of reaction substrates and products but even of short-lived reaction intermediates as they are present in solution possible [4] and provide new insights into the mechanism of the reactions studied, including important homogeneously catalyzed reactions. [5] Chen used ESIMS for the study of metathesis reaction primarily in the gas phase.…”

Section: Introductionmentioning

confidence: 99%

ESIMS Studies and Calculations on Alkali‐Metal Adduct Ions of Ruthenium Olefin Metathesis Catalysts and Their Catalytic Activity in Metathesis Reactions

Wang

Yim

Klüner

et al. 2009

Chemistry A European J

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Electrospray ionization mass spectrometry (ESIMS) and subsequent tandem mass spectrometry (MS/MS) analyses were used to study some important metathesis reactions with the first-generation ruthenium catalyst 1, focusing on the ruthenium complex intermediates in the catalytic cycle. In situ cationization with alkali cations (Li(+), Na(+), K(+), and Cs(+)) using a microreactor coupled directly to the ESI ion source allowed mass spectrometric detection and characterization of the ruthenium species present in solution and particularly the catalytically active monophosphine-ruthenium intermediates present in equilibrium with the respective bisphosphine-ruthenium species in solution. Moreover, the intrinsic catalytic activity of the cationized monophosphine-ruthenium complex 1 aK(+) was directly demonstrated by gas-phase reactions with 1-butene or ethene to give the propylidene Ru species 3 aK(+) and the methylidene Ru species 4 aK(+), respectively. Ring-closing metathesis (RCM) reactions of 1,6-heptadiene (5), 1,7-octadiene (6) and 1,8-nonadiene (7) were studied in the presence of KCl and the ruthenium alkylidene intermediates 8, 9, and 10, respectively, were detected as cationized monophosphine and bisphosphine ruthenium complexes. Acyclic diene metathesis (ADMET) polymerization of 1,9-decadiene (14) and ring-opening metathesis polymerization (ROMP) of cyclooctene (18) were studied analogously, and the expected ruthenium alkylidene intermediates were directly intercepted from reaction solution and characterized unambiguously by their isotopic patterns and ESIMS/MS. ADMET polymerization was not observed for 1,5-hexadiene (22), but the formation of the intramolecularly stabilized monophosphine ruthenium complex 23 a was seen. The ratio of the signal intensities of the respective with potassium cationized monophosphine and bisphosphine alkylidene Ru species varied from [I(4a)]/[I(4)]=0.02 to [I(23a)]/[I(23)]=10.2 and proved to be a sensitive and quantitative probe for intramolecular pi-complex formation of the monophosphine-ruthenium species and of double bonds in the alkylidene chain. MS/MS spectra revealed the intrinsic metathesis catalytic activity of the potassium adduct ions of the ruthenium alkylidene intermediates 8 a, 9 a, 10 a, 15 a, and 19 a, but not 23 a by elimination of the respective cycloalkene in the second step of RCM. Computations were performed to provide information about the structures of the alkali metal adduct ions of catalyst 1 and the influence of the alkali metal ions on the energy profile in the catalytic cycle of the metathesis reaction.

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Section: Introductionmentioning

confidence: 99%

ESIMS Studies and Calculations on Alkali‐Metal Adduct Ions of Ruthenium Olefin Metathesis Catalysts and Their Catalytic Activity in Metathesis Reactions

Wang

Yim

Klüner

et al. 2009

Chemistry A European J

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“…For the detection of intermediates and organometallic complexes in dilute homogeneous solutions, especially in IL systems, ESI-MS spectrometry is the most powerful and convenient tool, and is best known as ion fishing. [32][33][34][35][36][37][38] An aliquot of the reaction mixture was taken after 45 min (ca. 50 % conversion), and the sample was analyzed in Figure 6) showed the IL (m/ z = 182.07) and two ruthenium species with signal sets at around 518.81 and 552.76.…”

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confidence: 99%

Decomposition of Formic Acid Catalyzed by a Phosphine‐Free Ruthenium Complex in a Task‐Specific Ionic Liquid

2010

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The dehydrogenation of formic acid is effectively catalyzed by the Ru complex [{RuCl2(p‐cymene)}2] dissolved in the ionic liquid (IL) 1‐(2‐(diethylamino)ethyl)‐3‐methylimidazolium chloride at 80 °C without additional bases. This catalytic system gives TOF values of up to 1540 h−1. Preliminary kinetic insights show formal reaction orders of 0.70(±0.15), 0.78(±0.03) and 2.00(±0.17) for the Ru catalyst, IL 1, and formic acid, respectively. The apparent activation energy of this process is estimated to be (69.1±7.6) kJ mol−1. In addition, dimeric Ru hydride ionic species involved in the reaction, such as [{Ru(p‐cymene)}2{(H)μ‐(H)‐μ‐(HCO2)}]+ and [{Ru(p‐cymene)}2{(H)μ‐(Cl)μ‐(HCO2)}]+, are identified by mass spectrometry. The presence of water in large amounts inhibits higher conversions. Finally, a remarkable catalytic activity is observed during recycles, indicating this system’s potential for hydrogen gas production.

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“…Considering that other methods [9,10] were not superior, some thought was given to the reaction mechanism in the hope of designing an improved protocol. In the view of the zwitterionic nature of MBH reaction intermediates [11] (i.e., 7) and the lipophilic properties of cyclohexenone 6, it was surmised that a surfactant in water may well provide the ideal reaction medium to satisfy both requirements. Water offers many environmental and eco-nomical benefits, not to mention reactivity enhancement in some cases, [12] however, the combination with surfactants, most commonly in the form of micellar dispersions, [13] has been utilised in organic synthesis only sparingly.…”

Section: Resultsmentioning

confidence: 99%

Cyclic Enones as Substrates in the Morita–Baylis–Hillman Reaction: Surfactant Interactions, Scope and Scalability with an Emphasis on Formaldehyde

et al. 2009

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Traditionally, cyclic enones and formalin are reactants notorious for displaying problematic behaviour (i.e., poor solubility and low yields) under Morita-Baylis-Hillman (MBH) reaction conditions. The body of research presented herein focuses on the use of surfactants in water as a solvent medium that offers a resolution to many of the issues associated with the MBH reaction. Reaction scope, scalability and small angle X-ray scattering have been studied to assist with the understanding of the reaction mechanism and industrial application. A comparison against known literature methods for reaction scale-up is also discussed.

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Probing the Mechanism of the Baylis–Hillman Reaction by Electrospray Ionization Mass and Tandem Mass Spectrometry

Cited by 84 publications

References 56 publications

ESIMS Studies and Calculations on Alkali‐Metal Adduct Ions of Ruthenium Olefin Metathesis Catalysts and Their Catalytic Activity in Metathesis Reactions

ESIMS Studies and Calculations on Alkali‐Metal Adduct Ions of Ruthenium Olefin Metathesis Catalysts and Their Catalytic Activity in Metathesis Reactions

Decomposition of Formic Acid Catalyzed by a Phosphine‐Free Ruthenium Complex in a Task‐Specific Ionic Liquid

Cyclic Enones as Substrates in the Morita–Baylis–Hillman Reaction: Surfactant Interactions, Scope and Scalability with an Emphasis on Formaldehyde

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