Von vierfach funktionalisierten Cyclophanen zu rohrförmigen Molekülen

Schröder, Axel; Karbach, Detlef; Güther, Ralf; Vögtle, Fritz

doi:10.1002/cber.19921250815

Cited by 33 publications

(15 citation statements)

References 20 publications

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“…We carried out model studies (17) as the synthetic target, as it contains the representative structural unit of [6.8] n cyclacenes. For a stepwise synthetic approach we found that the McMurry coupling of dialdehyde 18 yielded 17 (Scheme 5).…”

Section: Resultsmentioning

confidence: 99%

From Metacyclophanes to Cyclacenes: Synthesis and Properties of [6.8]₃Cyclacene

Esser

Bandyopadhyay

Röminger

et al. 2009

Chemistry A European J

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In this article we show synthetic pathways to [6.8](n)cyclacenes demonstrated by the de novo synthesis of [6.8](3)cyclacene as the first purely hydrocarbon cyclacene and of precursors for [6.8](4)cyclacene. The design of the de novo synthesis by exploring alternative pathways is discussed and various precursors are shown. Crucial to the synthesis of [6.8](3)cyclacene were two cyclization steps. The first is a Wittig trimerization reaction which yielded the hexamethyl substituted all-cis-[2(3)]metacyclophanetriene. For the second cyclization step the methyl groups were converted to aldehyde functionalities by two subsequent oxidation steps of N-bromosuccinimide (NBS) bromination and oxidation with 2-iodoxybenzoic acid (IBX). The final cyclization of the second set of double bonds was achieved by a McMurry-coupling reaction. Towards the synthesis of [6.8](4)cyclacene different synthetic pathways to methyl substituted all-cis-[2(4)]metacyclophanetetraenes were explored. Insights into the structures of [2(3)]metacyclophanetri- and [2(4)]metacyclophanetetraenes were gained by X-ray crystallographic investigations on various intermediates. A crystallographic analysis of [6.8](3)cyclacene revealed a D(3h) symmetrical structure with planar benzene rings and a formation of tubular structures in the solid state.

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Section: Resultsmentioning

confidence: 99%

From Metacyclophanes to Cyclacenes: Synthesis and Properties of [6.8]₃Cyclacene

Esser

Bandyopadhyay

Röminger

et al. 2009

Chemistry A European J

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“…Hexaester diol (7): To a solution of tetrol 4 [24] (0.5 g, 0.76 mmol) in dry 1-methyl-2-pyrrolidinone (NMP) (500 mL) was added anhydrous Cs 2 CO 3 (4.0 g) and the solution was degassed. The degassed solution of diester 6 [25] (0.47 g, 1.1 mmol; 1.5 equivalents) was added dropwise over 16 h to the solution of tetrol 4. After the mixture had been stirred under nitrogen for 24 h, it was poured into 1 L of a 1:1 mixture of distilled water and a saturated solution of NaCl.…”

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confidence: 99%

“…Tetrol 4 and diester 6 were prepared by methods described elsewhere. [24] , [25] 1 H NMR spectra were obtained with a Varian Unity-plus NMR spectrometer. Hexaester diol (7): To a solution of tetrol 4 [24] (0.5 g, 0.76 mmol) in dry 1-methyl-2-pyrrolidinone (NMP) (500 mL) was added anhydrous Cs 2 CO 3 (4.0 g) and the solution was degassed.…”

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confidence: 99%

Highly Organized Spherical Hosts That Bind Organic Guests in Aqueous Solution with Micromolar Affinity: Microcalorimetry Studies

Piatnitski

Flowers

Deshayes³

2000

Chem. Eur. J.

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Two novel closed-shell hemicarcerand-like hosts with spherical cavities of 11 A diameter that are soluble in aqueous solution were constructed. The binding of xylenes, aryl ethers, polyaromatic compounds, ferrocene derivatives, and bicyclic aliphatic compounds were examined by NMR spectroscopy and microcalorimetry. NMR binding studies indicated that binding depended upon guest hydrophobicity and shape. No binding was detected for guests in which a charge must be desolvated as part of inclusion or for guests that can not fit within the cavity of the host. Three complexes 2.naphthalene, 2.p-xylene, and 2.ferrocene were isolated and found to be indefinitely stable in the solid phase and in aqueous solution. The binding constants for these complexes are estimated to be greater than 10(8) M-1. Thirteen guests were examined by microcalorimetry with binding constants ranging between 10(7) and 10(3) M-1. A comparison of results obtained here with those from previous work with beta-cyclodextrin and cyclophane hosts, along with analysis of the entropy-enthalpy compensation data, indicate that there is a higher degree of guest desolvation with this host structure than with open-shell hosts. This accounts at least partially for the increase in affinity observed with these closed-shell hosts. Replacing a hydroxy group in the host portal with a hydrogen atom does not affect the binding constant, a finding consistent with the guest residing deeply buried within the host cavity. It was observed that aromatic guests are bound with higher affinity than aliphatic ones in agreement with results that point to the importance of London dispersion forces in the association of aromatic components in face-to-edge orientations. The correlation of changes in NMR chemical shift with microcalorimetry data supports a model in which increased CH-pi interactions strengthen association between host and guest due to the dominant role of van der Waals dispersion forces. Remarkably, the binding constant for the 1,4 isomer of dimethoxybenzene is 32 times higher than for the 1,2 isomer, and even greater discrimination is observed between the xylene guests since the binding constant for p-xylene is 80 times greater than that for o-xylene. This discrimination between isomeric guests by a rigid host indicates that changes in specific hydrophobic interactions have substantial effects upon binding affinity.

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“…Oxidation of the hydroxyl groups to 24 failed, as well as the direct reduction of 22 to 24 with DIBAL‐H, because of the formation of a lactone. 4,6‐Bis(bromomethyl)isophthalaldehyde ( 26 ) was synthesized from diethyl 4,6‐bis(bromomethyl)isophthalate ( 25 ),17 but transformation to the phosphonium salt 27 failed for reasons of product isolation. As our attempts to synthesize the desired precursors for multicomponent one‐pot reactions were not successful, we focused on a stepwise approach for the synthesis of [6.8] n cyclacenes.…”

Section: Resultsmentioning

confidence: 99%

Comparison of Force Fields on the Basis of Various Model Approaches—How To Design the Best Model for the [C_nMIM][NTf₂] Family of Ionic Liquids

2013

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In this contribution, we present two new united-atom force fields (UA-FFs) for 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C(n)MIM][NTf(2)] (n=1, 2, 4, 6, 8) ionic liquids (ILs). One is parametrized manually, and the other is developed with the gradient-based optimization workflow (GROW). By doing so, we wanted to perform a hard test to determine how researchers could benefit from semiautomated optimization procedures. As with our already published all-atom force field (AA-FF) for [C(n)MIM][NTf(2)] (T. Köddermann, D. Paschek, R. Ludwig, ChemPhysChem- 2007, 8, 2464), the new force fields were derived to fit experimental densities, self-diffusion coefficients, and NMR rotational correlation times for the IL cation and for water molecules dissolved in [C(2)MIM][NTf(2)]. In the manual force field, the alkyl chains of the cation and the CF3 groups of the anion were treated as united atoms. In the GROW force field, only the alkyl chains of the cation were united. All other parts of the structures of the ions remained unchanged to prevent any loss of physical information. Structural, dynamic, and thermodynamic properties such as viscosity, cation rotational correlation times, and heats of vaporization calculated with the new force fields were compared with values simulated with the previous AA-FF and the experimental data. All simulated properties were in excellent agreement with the experimental values. Altogether, the UA-FFs are slightly superior for speed-up reasons. The UA-FF speeds up the simulation by about 100 % and reduces the demanded disk space by about 78 %. More importantly, real time and efforts to generate force fields could be significantly reduced by utilizing GROW. The real time for the GROW parametrization in this work was 2 months. Manual parametrization, in contrast, may take up to 12 months, and this is, therefore, a significant increase in speed, though it is difficult to estimate the duration of manual parametrization.

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Von vierfach funktionalisierten Cyclophanen zu rohrförmigen Molekülen

Cited by 33 publications

References 20 publications

From Metacyclophanes to Cyclacenes: Synthesis and Properties of [6.8]₃Cyclacene

From Metacyclophanes to Cyclacenes: Synthesis and Properties of [6.8]₃Cyclacene

Highly Organized Spherical Hosts That Bind Organic Guests in Aqueous Solution with Micromolar Affinity: Microcalorimetry Studies

Comparison of Force Fields on the Basis of Various Model Approaches—How To Design the Best Model for the [C_nMIM][NTf₂] Family of Ionic Liquids

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Von vierfach funktionalisierten Cyclophanen zu rohrförmigen Molekülen

Cited by 33 publications

References 20 publications

From Metacyclophanes to Cyclacenes: Synthesis and Properties of [6.8]3Cyclacene

From Metacyclophanes to Cyclacenes: Synthesis and Properties of [6.8]3Cyclacene

Highly Organized Spherical Hosts That Bind Organic Guests in Aqueous Solution with Micromolar Affinity: Microcalorimetry Studies

Comparison of Force Fields on the Basis of Various Model Approaches—How To Design the Best Model for the [CnMIM][NTf2] Family of Ionic Liquids

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From Metacyclophanes to Cyclacenes: Synthesis and Properties of [6.8]₃Cyclacene

From Metacyclophanes to Cyclacenes: Synthesis and Properties of [6.8]₃Cyclacene

Comparison of Force Fields on the Basis of Various Model Approaches—How To Design the Best Model for the [C_nMIM][NTf₂] Family of Ionic Liquids