Metathesis in Pure Water Mediated by Supramolecular Additives

Brendgen, Thomas; Fahlbusch, Tilmann; Frank, M.; Schühle, Daniel T.; Seßler, M.; Schatz, J.

doi:10.1002/adsc.200800637

Cited by 45 publications

(27 citation statements)

References 46 publications

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“…[38] Furthermore, di(methoxy)imidazolium-based salts are used for enhancing reactions in water. [43] As experimental method, we use ARXPS for probing the surface layer of the IL samples. Our Dual Analyzer System for Surface Analysis (DASSA) [44] setup allows for simultaneously recording spectra in a surface sensitive and a bulk sensitive mode, which directly permits to identify surface enrichment or depletion effects of all atoms (apart from hydrogen) being present in the ions.…”

Section: Introductionmentioning

confidence: 99%

Surface Enrichment in Equimolar Mixtures of Non‐Functionalized and Functionalized Imidazolium‐Based Ionic Liquids

et al. 2018

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For equimolar mixtures of ionic liquids with imidazolium‐based cations of very different electronic structure, we observe very pronounced surface enrichment effects by angle‐resolved X‐ray photoelectron spectroscopy (XPS). For a mixture with the same anion, that is, 1‐methyl‐3‐octylimidazolium hexafluorophosphate+1,3‐di(methoxy)imidazolium hexafluorophosphate ([C8C1Im][PF6]+[(MeO)2Im][PF6]), we find a strong enrichment of the octyl chain‐containing [C8C1Im]+ cation and a corresponding depletion of the [(MeO)2Im]+ cation in the topmost layer. For a mixture with different cations and anions, that is, [C8C1Im][Tf2N]+[(MeO)2Im][PF6], we find both surface enrichment of the [C8C1Im]+ cation and the [Tf2N]− (bis[(trifluoromethyl)sulfonyl]imide) anion, while [(MeO)2Im]+ and [PF6]− are depleted from the surface. We propose that the observed behavior in these mixtures is due to a lowering of the surface tension by the enriched components. Interestingly, we observe pronounced differences in the chemical shifts of the imidazolium ring signals of the [(MeO)2Im]+ cations as compared to the non‐functionalized cations. Calculations of the electronic structure and the intramolecular partial charge distribution of the cations contribute to interpreting these shifts for the two different cations.

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Section: Introductionmentioning

confidence: 99%

Surface Enrichment in Equimolar Mixtures of Non‐Functionalized and Functionalized Imidazolium‐Based Ionic Liquids

et al. 2018

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“…In summary,w eh ave shown that 1a and 1b act as as upramolecular containers for a,w-dienes in D 2 Ot og ive extended, coiled, and folded guest complexes as homogeneous solutions.T he cavitand 1b not only dissolves the substrate but also plays arole as template for RCM reactions with aw ater-compatible catalyst. [23] Theh ost-guest interactions bring the reacting ends closer together in aprecyclization conformation that overcomes some internal strains.The yield of seven, eight, and nine-membered cycloalkenes were significantly enhanced even compared with the reaction in homogeneous chloroform phase.T he cavitand buries hydrophobic surfaces and the shape of the space on offer pushes the reactions along congruent pathway,e ven some that are not readily observed in bulk solution.…”

Section: Angewandte Chemiementioning

confidence: 99%

Cavitands as Containers for α,ω‐Dienes and Chaperones for Olefin Metathesis

Petsalakis

Theodorakopoulos

et al. 2018

Angew Chem Int Ed

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Described herein is the behavior of a,w-dienes sequestered within cavitands in aqueous (D 2 O) solution. Hydrophobic forces drive the dienes into the cavitands in conformations that best fill the available space.Shorter dienes (C9 and C10) bind in compressed conformations that tumble rapidly in the cavitands.L onger dienes induce capsule formation between cavitands with self-complementary hydrogen bonding sites,w here the dienes exist in extended conformations.Incavitands unable to form capsules,longer dienes adopt folded structures.T he wider open ends allowt he synthesis of medium-sized cycloalkenes by ring-closing metathesis reactions with the Hoveyda-Grubbs-II catalyst. Yields of cycloheptene and cyclooctene were enhanced by the chaperones in water when compared with reactions of the free dienes in either aqueous media or chloroform, and even cyclononene could be prepared within the cavitand.Molecularcontainerhostshavereceivedmuchattentionfor their ability to confine guest molecules and affect their reactivity.T he use of self-assembly has expanded the use of these containers for the promotion of reactions in small spaces. [1] We recently reported the synthesis and characterization of the deep cavitand 1a [2] (Figure 1). Thes elfcomplementary pattern of hydrogen bond donors and acceptors on the upper rim was devised by de Mendoza, [3] who showed that dimerization to host capsules occurs with suitable guests in organic solvents.W ef ound that pyridinium or methylimidazolium "feet" provided good solubility in water, and the formation of capsules occurs even in aqueous solutions when large hydrophobic guests are present. [4] To prevent such dimerization, we exhaustively N-methylated the benzimidazolones of the upper rim to form the octamethyl urea 1b (Supporting Information). Thec avitand 1b showed good solubility in water (D 2 O), where it exists as avelcrand [5] dimer in the absence of guests.H erein we report the complexation of symmetrical aliphatic a,w-dienes (C9-C14) with cavitands 1a and 1b,a nd their applications for olefin metathesis in otherwise reluctant cyclizations.Alkenes bound inside synthetic host structures are not often reported [6] because the NMR signals of the olefinic protons are rarely observed given the overlap with the signals of the cavitands. [7] We used commercially available a,w-dienes:C 91 ,8-nonadiene (2a), C10 1,9-decadiene (2b), C11 1,10-undecadiene (2c), C12 1,11-dodecadiene (2d), and C14 1,13-tetradecadiene (2f). TheC13 1,12-tridecadiene (2e) was synthesized by reaction of 10-bromo-1-decene with allylmagnesium bromide. [8] Brief sonication of these a,w-dienes (0.5 mm)w ith 1a (0.5 mm)i nw ater (D 2 O) gave host-guest complexes with 1 HNMR signals of the guest characteristically upfield-shifted by the shielding of the aromatic panels of the host structure (Figure 2; Supporting Information). Thelonger a,w-dienes 2c, 2d, 2e,and 2fshow signals that are spread out between d = 1.5 and À2.0 ppm (Figure 2). Thes ignals for terminal vinyl hydrogen of C11 appears at d = 0.05 ppm (Dd = À...

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“…Metathesis reactions are of high interest because of their tolerance to a variety of functional groups, high yield, and potential chemoselectivity, even of olefins with different substituents, allowing specific cross metathesis reactions. The design of novel, water‐soluble Grubbs catalysts such as the water‐soluble Hoyveda‐Grubbs catalyst (HG2‐S 3 ) and the development of novel protocols to allow the use of GI and GII in emulsion have increased interest in the application of metathesis catalysts under aqueous conditions . The use of ROMP in the preparation of biopolymer networks has high potential for biopolymers that are water soluble and show limited solubility in organic solvents.…”

Section: Introductionmentioning

confidence: 99%

“…The design of novel, water-soluble Grubbs catalysts such as the water-soluble Hoyveda-Grubbs catalyst (HG2-S 3) and the development of novel protocols to allow the use of GI and GII in emulsion have increased interest in the application of metathesis catalysts under aqueous conditions. [13][14][15] The use of ROMP in the preparation of biopolymer networks has high potential for biopolymers that are water soluble and show limited solubility in organic solvents. The orthogonality of the metathesis reaction furthermore allows such crosslinking with high chemoselectivity also in the presence of -OH, -NH 2 , or -COOH groups and is only initiated when a suitable catalyst is added.…”

Section: Introductionmentioning

confidence: 99%

Crosslinking of gelatin by ring opening metathesis under aqueous conditions—an exploratory study

Neffe

Chua

Luetzow

et al. 2014

Polymers for Advanced Techs

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Ring‐opening metathesis catalysis has received little attention as a means to functionalize or crosslink biopolymers in water since the required catalysts are usually not stable under these conditions. However, biopolymer solubility suggests such a procedure. We show that Grubbs first and second generation catalysts (in emulsion) as well as a water‐soluble Hoveyda‐Grubbs catalyst can be applied to crosslink glycidyl methacrylated gelatin with norbornene dicarboxylic acid in water by a cross metathesis‐ring opening metathesis approach. A mechanistic study suggests that cross metathesis between the functionalized polymer and the cyclic olefin acts as an initiating step for the crosslinking reaction. Copyright © 2014 John Wiley & Sons, Ltd.

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Metathesis in Pure Water Mediated by Supramolecular Additives

Cited by 45 publications

References 46 publications

Surface Enrichment in Equimolar Mixtures of Non‐Functionalized and Functionalized Imidazolium‐Based Ionic Liquids

Surface Enrichment in Equimolar Mixtures of Non‐Functionalized and Functionalized Imidazolium‐Based Ionic Liquids

Cavitands as Containers for α,ω‐Dienes and Chaperones for Olefin Metathesis

Crosslinking of gelatin by ring opening metathesis under aqueous conditions—an exploratory study

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