- On the Synthesis of Monoamides of 18-Crown-6-tetracarboxylic Acid
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The synthesis of monoamides of (R,R,R,R)-18-crown-6-2,3,11,12-tetracarboxylic acid via reaction of primary and secondary amines with the crown ether bis-anhydride is explored, One equivalent of benzylamine gave a quantitative yield of a diamide, and the r
- Cross,Fyles
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- The H3O+ Cation: Molecular Structure of an Oxonium-Macrocycle Polyether Complex
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The oxonium ion has been isolated as a discrete entity by inclusion into a macrocyclic cavity.The structure of the complex formed by a tetracarboxylic 18-crown-6 ligand with H3O+ has been determined by X-ray crystallography (P212121; a = 10.526 (2); b = 14.325 (2), and c= 15.324 (2) Angstroem).The structure was solved by direct methods and refined to R = 0.048 for 1957 (I 2?(I)) reflections.Hydrogen atoms were located on a Fourier difference map.The overall shape of the ligand is similar to that found in related complexes, as two carboxylic acid groups extend on both sides of the pseudoplanar macrocycle.The H3O+ cation is anchored in the center of the cavity by three OH+...O hydrogen bonds (2.67, 2.73, and 2.74 Angstroem) whereas the chloride counterion is H bonded to the three carboxylic acid groups 5.5 Angstroem away from the cation.The pyramidal geometry found for the oxonium cation in the present molecular complex shows this conformation to be the most stable in an ion-solvating environment.
- Behr, Jean-Paul,Dumas, Philippe,Moras, Dino
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- Molecular Receptors. Functionalized and Chiral Macrocyclic Polyethers Derived from Tartaric Acid
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A number of functionalized and chiral macrocyclic polyethers have been synthesized by condensation of the dithallium alcoholate of (R,R)-(+)-tartaric acid derivatives with α,ω-dihalides.In this way for instance, the tetracarboxylic -O6 macrocycle 3c a
- Behr, Jean-Paul,Girodeau, Jean-Marc,Hayward, Rodney C.,Lehn, Jean-Marie,Sauvage, Jean-Pierre
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p. 2096 - 2111
(2007/10/02)
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