4H-Pyran and pyrylium hemispherands: Partly preorganized ionophores with reactive molecular cavities

Dijkstra, Pieter J.; Hertog, H. J. den; Eerden, J. Van; Harkema, Sybolt; Reinhoudt, David N.

doi:10.1021/jo00237a027

Cited by 26 publications

(1 citation statement)

References 2 publications

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“…Crystal structures of the uncomplexed 4-pyridohemispherand (Dijkstra, den Hertog, van Eerden, Harkema & Reinhoudt, 1988), the Na.picrate complex (Dijkstra, den Hertog, van Steen, Zijlstra, Skowronska-Ptasinska, Reinhoudt, van Eerden & Harkema, 1987) Upon complexation of water but also with Na + and malononitrile a rather strong reorganization takes place: in the crystal structure of the uncomplexed ligand the two methoxy groups are on either side of the mean macrocyclic plane, whereby one of the methoxy groups partly converges into the cavity which is partly filled by the methyl groups.…”

Section: Related Literaturementioning

confidence: 99%

Complexation of water by a 4-phenylpyridohemispherand

Dijkstra¹,

Hertog²,

Reinhoudt³

et al. 1991

Acta Crystallogr C

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Abstract. 25,16,. ~ i]_ heptacosa-I (25), 2,4,6(27),7,9,11 (26),21,23-nonaene perchlorate-ethanol-water (1 / 1 / 1), C33H36NO~ -.-C104.C2HsOH.H20, Mr = 690-2, orthorhombic, Pca2~, a = 27.747 (5), b = 9.572 (3), c = 12.866 (4) A,, V= 3417 (3) A 3, Z = 4, Dx = 1-39 g cm-3, a(Mo Ka)=0"7107A, #=1.69cm-~, F(000)=1464, T= 100 (5)K, final R = 6.5% for 2915 observed reflections. The water molecule is complexed in the cavity of the macrocycle with hydrogen bonds to the polyethylene oxy atoms adjacent to the outer phenyl rings of the terphenyl unit. The O atom of the water molecule accepts hydrogen bonds from the pyridinium proton and the OH proton of the ethanol molecule. The HC104 proton is transferred to the pyrido nitrogen.Experimental. The title compound was prepared by dissolving 50 mg (0-09 mmol) of the 4-phenylpyridohemispherand (Dijkstra, den Hertog, van Steen, Zijlstra, Skowronska-Ptasinska, Reinhoudt, van Eerden & Harkema, 1987) in 2 ml of ethanol and the slow addition of 0.5 ml of 70% HC104. Slow evaporation of solvent afforded colorless crystals of the complex suitable for X-ray diffraction, m.p. 496 K (dec.).Intensities were measured at 100 (5)K on an Enraf-Nonius CAD-4 diffractometer using graphite- H atoms of the macrocycle were placed in calculated positions and treated as riding on their parent atoms (bond distance 0.95/k, B~so = 4.0 A2), with the exception of the methyl hydrogens. These atoms and the H atoms of the water molecule were found from a difference Fourier synthesis. Positions of these atoms were refined. Hydrogens of the ethanol group could not be located (probably due to the large thermal motions). These hydrogens were not included in the refinement. In order to fix the origin in the c direction, the z parameter of the C1 atom has been fixed.The structure was solved with MULTAN (Germain, Main & Woolfson, 1971) and refined by full-matrix least squares. Weights for each reflection in the refinement (on F) were calculated from w = 4Fo2/0.2(Fo2), ov2(Fo2) = 0"2(/)+ (pFo2)2; the value of the instability factor p was determined as 0.04. The number of parameters refined was 457: scale factor, isotropic extinction factor [final value 2.4 (7) x 10-9], positional and anisotropic thermal parameters for the non-H atoms positional parameters of some H atoms.Refinement converged at R = 6-5%, wR = 6.3%, S = 1.64, (A/o')max = 0"2. Largest peak on the final difference Fourier map 0.54 e A -3 (in the perchlorate ion). All calculations were performed using SDP

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Section: Related Literaturementioning

confidence: 99%

Complexation of water by a 4-phenylpyridohemispherand

Dijkstra¹,

Hertog²,

Reinhoudt³

et al. 1991

Acta Crystallogr C

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Host‐Guest Interactions in Thin Membranes: Selective Ion Transport and Transduction into Electronic Signals

Reinhoudt

Nijenhuis

Wal

2007

Ciba Foundation Symposium 158 ‐ Host‐Guest Molecular Interactions: From Chemistry to Biology

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Wohl‐Ziegler Bromination

2010

Comprehensive Organic Name Reactions and Reagents

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This reaction is the bromination of unsaturated organic compounds at either allylic or benzylic position (or α‐position of the side chain of other aromatic compounds) using N ‐bromosuccinimide (NBS) as the bromination reagent. The bromination by N ‐bromoacetamide is simply referred to as the Wohl reaction, whereas the bromination by NBS is generally known as the Wohl–Ziegler bromination. Besides N ‐bromosuccinimide (NBS), several bromination reagents have been recommended for this reaction. The N ‐bromosuccinimide is an ideal bromination reagent for the allylic bromination. It has been reported that the Wohl–Ziegler bromination does not work for the conjugated olefins and 1,4‐dienes, which are the inhibitors for the Wohl–Ziegler bromination. Furthermore, the bromination of benzyl compounds, primary benzyl methyl ethers and p ‐nitrobenzyl methyl ether have been discussed. In addition, the electrophilic bromination on the activated aromatic compounds with NBS often occurs in the presence of an acidic catalyst. This reaction has wide application in organic synthesis for generating allylic and benzylic bromides.

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4H-Pyran and pyrylium hemispherands: Partly preorganized ionophores with reactive molecular cavities

Cited by 26 publications

References 2 publications

Complexation of water by a 4-phenylpyridohemispherand

Complexation of water by a 4-phenylpyridohemispherand

Host‐Guest Interactions in Thin Membranes: Selective Ion Transport and Transduction into Electronic Signals

Wohl‐Ziegler Bromination

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