- Binding features of molecular clips derived from diphenylglycoluril
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The structure and binding properties of a series of receptor molecules based on the building block diphenylglycoluril are described. These receptors bind dihydroxy-substituted aromatic guests in chloroform solution by means of hydrogen bonding and π-π stacking interactions. IR difference spectroscopy shows that the hydrogen bonds are formed between the OH groups of the guest molecule and the π-electrons of the urea carbonyl groups present in the receptor. The structure of the complexes was further investigated by comparing the complexation-induced shifts in the 1H NMR spectra with the calculated shifts for a number of geometries of the host-guest complexes. These data demonstrate that the guest molecules are clamped within the cavity of the receptor.
- Sijbesma,Kentgens,Lutz,Van Der Maas,Nolte
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p. 8999 - 9005
(2007/10/02)
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- Bromophloroglucinols and their methyl ethers
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All 16 bromination products of phloroglucinol and its methyl ethers, as well as five bromoresorcinols and three of their dimethyl ethers, were synthesized and analyzed by nuclear magnetic resonance spectroscopy.Two or three equivalents of bromine convert phloroglucinol to di- and tribromophloroglucinol, 5-methoxyresorcinol to the tri- and 2,4-dibromo, 3,5-dimethoxyphenol to the tri- and 2,6-dibromo, and 1,3,5-trimethoxybenzene to the dibromo compound.With one equivalent of bromine, 3,5-dimethoxyphenol reacts preferentially at C-2 while 5-methoxyresorcinol gives both monobromo isomers.Partial debromination with sodium sulfite yields successively 2,4-dibromo- and 2-bromo-5-methoxyresorcinol from the tribromo compound but fails with brominated 3,5-dimethoxyphenol.In the resorcinol series, C-2 is invariably the least reactive position. 4,6-Dibromo-5-methoxyresorcinol and 2,4-dibromo-3,5-dimethoxyphenol are accessible by methylation of dibromophloroglucinol, obtained from 3,5-dibromo-2,4,6-trihydroxybenzoic acid by decarboxylation.In contrast to resorcinol and tribromoresorcinol, the partial bromination of pholoroglucinol and debromination of tribromopholoroglucinol are not selective.The 13Cnmr spectra of bromophloroglucinol methyl ethers show characteristic downfield shifts for methoxy groups orthogonal to the aromatic ring plane.
- Kiehlmann, E.,Lauener, R. W.
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p. 335 - 344
(2007/10/02)
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