Organic reactions in liquid crystalline solvents. 2. An investigation into the use of liquid crystalline solvents to effect stereochemical control in the Diels–Alder reaction

Leigh, William J.

doi:10.1139/v85-455

Cited by 13 publications

(3 citation statements)

References 4 publications

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“…Didemnenones C (3, 0.007% dry weight) and D (4, 0.006% dry weight) were isolated from the methanol extract of D. voeltzkowi following solvent partitioning and Sephadex LH-20 (MeOH/ CHC13, 1/1) chromatography. Their NMR spectra were essentially identical and showed many similarities with the spectra of didemnenones A (1) and B (2).8,9 A decisive experiment was (4) The crude extract was dissolved in MeOH, mixed with silica gel, and evaporated to dryness prior to chromatography. (5) Compound 5 crystallized in the monoclinic space group P2¡ with a = 7.662 (1) A, b = 7.709 (1) A, c = 9.808 (1) A, and ß = 104.308 (13)°, and one molecule of composition C12H1404 forming the asymmetric unit.…”

mentioning

confidence: 97%

X-ray absorption study of octafluorodirhenate(III): EXAFS structures and resonance Raman spectroscopy of octahalodirhenates

Conradson¹,

Sattelberger²,

Woodruff³

1988

J. Am. Chem. Soc.

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confidence: 97%

X-ray absorption study of octafluorodirhenate(III): EXAFS structures and resonance Raman spectroscopy of octahalodirhenates

Conradson¹,

Sattelberger²,

Woodruff³

1988

J. Am. Chem. Soc.

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“…This can be exemplified by the work of Leigh and co‐workers who showed, for example, how the trans / cis isomerisation of 1,2‐di(4‐cyanophenyl)‐1,2‐diphenylethylene was slowed in LC solvents compared to isotropic solvents or how the regiochemistry of the Diels–Alder addition of N ‐biphenylmaleimide to cholesta‐5,7‐dien‐3β‐yl acetate was influenced by carrying out the reaction in the LC mesophase . Curiously, however, in studying the Diels–Alder reaction between 2,5‐dimethyl‐3,4‐diphenylcyclopentadienone and a variety of dienophiles, no effect of LC solvent was observed, which was tentatively attributed both to lack of discrimination in solvating the two transition states and also the high tendency for the diene to destabilise the LC phase of the solvents used . Therefore, the nature of the effect being observed is not necessarily a generalised phenomenon.…”

Section: Resultsmentioning

confidence: 99%

Liquid‐Crystalline Ionic Liquids as Ordered Reaction Media for the Diels–Alder Reaction

Bruce

Gao

Lopes

et al. 2016

Chemistry A European J

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Liquid-crystalline ionic liquids (LCILs) are ordered materials that have untapped potential to be used as reaction media for synthetic chemistry. This paper investigates the potential for the ordered structures of LCILs to influence the stereochemical outcome of the Diels-Alder reaction between cyclopentadiene and methyl acrylate. The ratio of endo- to exo-product from this reaction was monitored for a range of ionic liquids (ILs) and LCILs. Comparison of the endo:exo ratios in these reactions as a function of cation, anion and liquid crystallinity of the reaction media, allowed for the effects of liquid crystallinity to be distinguished from anion effects or cation alkyl chain length effects. These data strongly suggest that the proportion of exo-product increases as the reaction media is changed from an isotropic IL to a LCIL. A detailed molecular dynamics (MD) study suggests that this effect is related to different hydrogen bonding interactions between the reaction media and the exo- and endo-transition states in solvents with layered, smectic ordering compared to those that are isotropic.

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“…In addition, recent works by Leigh et al reported the use of liquid-crystalline solvents to control the relative stereochemistry in Diels-Alder reactions; all of the mesophases investigated display no ability in discriminating endo versus exo product formation, in either isotropic, cholesteric or smectic solvents [19][20].…”

Section: Introductionmentioning

confidence: 99%

Searching for asymmetric inductions in chiral smectic mesophases

Finzi¹,

Maccagnani²,

Masiero³

et al. 1989

Liquid Crystals

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Searching for asymmetric synthesis in smectic phases is, to our knowledge, reported for the first time in this paper. Two different reactions able to lead to optical enrichment were carried out in smectic phases (S) composed of chiral molecules. The first was a thermally promoted 1,3 dipolar cycloaddition of a diazo compound to a prochiral thiocarbonyl derivative run in a chiral smectic C mesophase (S,*). The second was a monomolecular process, the photochemical inversion of chiral sulphoxides in a smectic A mesophase. In both cases the asymmetric induction was zero or, in the best run, very very poor. This lack of transfer of chirality between the smectic solvent and the reaction is discussed to understand better the requirements for more successful tailoring of such experiments. IntroductionMany of the processes taking place in biological systems (such as enzymatic catalysis [l]) are determined not only by the chemistry of the individual reagents, products and biological catalysers, but also, by the specific interactions between these species with themselves and with their environment. That is why part of synthetic chemistry is today engaged in obtaining multi-molecular systems with a high degree of internal organization, able to reproduce the activity of molecules occurring in natural systems [2, 31, or able to be used as simplified models in order to study the effect of supramolecular parameters on the path of the reaction [4]. The reactivity of solute molecules can be modified within structurally organized solvents (such as liquid crystals [5-71, vesicles [8], micelles [9, 101 and membranes [ll]). These reactivity controls can be considered as true catalytic effects and are determined by anisotropic restrictions exerted on the orientational and diffusional properties of the reagent molecules and in some cases also by preferential solubilities in structurally different regions inside the solution.Being interested in performing asymmetric transformations assisted either by chiral auxiliaries or by a chiral medium, we decided to study the effects that smectic phases of liquid-crystalline solvents composed of chiral molecules could exert on the stereochemical outcome of properly chosen reactions.The availability of chiral mesomorphic molecules exhibiting smectic phases is now increasing because of possible applications to the display industry. These materials can therefore be used also as solvents for organic reactions. We turned our search for asymmetric induction to smectic mesophases because our group recently demonstrated that S, liquid crystals provide the most efficient way to carry out quaternization reactions of aminobenzene sulphonate esters [ 121. We have demonstrated that S,

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Organic reactions in liquid crystalline solvents. 2. An investigation into the use of liquid crystalline solvents to effect stereochemical control in the Diels–Alder reaction

Cited by 13 publications

References 4 publications

X-ray absorption study of octafluorodirhenate(III): EXAFS structures and resonance Raman spectroscopy of octahalodirhenates

X-ray absorption study of octafluorodirhenate(III): EXAFS structures and resonance Raman spectroscopy of octahalodirhenates

Liquid‐Crystalline Ionic Liquids as Ordered Reaction Media for the Diels–Alder Reaction

Searching for asymmetric inductions in chiral smectic mesophases

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