Hydrogen-Bond Symmetry in Difluoromaleate Monoanion
摘要:
The symmetry of the hydrogen bond in hydrogen difluoromaleate monoanion is probed by X-ray crystallography and by the NMR method of isotopic perturbation in water, in two aprotic organic solvents, and in an isotropic liquid crystal. The X-ray crystal structure of potassium hydrogen difluoromaleate shows a remarkably short O-O distance of 2.41 angstrom and equal O-H distances of 1.206 angstrom, consistent with a strong and symmetric hydrogen bond. Incorporation of O-18 into one carboxyl group allows investigation of the symmetry of the H-bond in solution by the method of isotopic perturbation. The F-19 NMR spectra of the mono-O-18-substituted monoanion in water, CD2Cl2, and CD3CN show an AB spin system, corresponding to fluorines in different environments. The difference is attributed to the perturbation of the acidity of a carboxylic acid by O-18, not to the mere presence of the O-18, because the mono-O-18 dianion shows equivalent fluorines. Therefore, it is concluded that the monoanion exists as an equilibrating pair of interconverting tautomers and not as a single symmetric structure not only in water but also in organic solvents. However, in the isotropic liquid crystal phase of 4-cyanophenyl 4-heptylbenzoate, tetrabutylammonium hydrogen difluoromaleate-O-18 shows equivalent fluorines, consistent with a single symmetric structure. These results support earlier studies, which suggested that the symmetry of hydrogen bonds can be determined by the local environment.
Process for the preparation of difluoromaleic anhydride
申请人:E. I. Du Pont de Nemours and Company
公开号:US05112993A1
公开(公告)日:1992-05-12
A process for producing difluoromaleic anhydride by reacting sulfur trioxide with a fluorinated precursor selected from the group consisting of hexafluoro-2,5-dihydrofuran, hexafluoro-2,5-dihydrothiophene, difluoro-2,5-dihydrothiophene-2,5-dione and tetrafluoro-2,5-dihydrothiophene-2-one. Also disclosed are the compounds difluoro-2,5-dihydrothiophene-2,5-dione and tetrafluoro-2,5-dihydrothiophene-2-one. Difluoromaleic anhydride is useful for example as a component of fluoropolymers.
[EN] TRIAZOLE DERIVATIVES AS WNT SIGNALING PATHWAY INHIBITORS<br/>[FR] DÉRIVÉS DE TRIAZOLE EN TANT QU'INHIBITEURS DE LA VOIE DE SIGNALISATION WNT
申请人:OSLO UNIVERSITY HOSPITAL HF
公开号:WO2012076898A1
公开(公告)日:2012-06-14
The present invention relates to compounds of formula (I), to processes for their preparation, to pharmaceutical formulations containing such compounds and to their use in therapy: Such compounds find particular use in the treatment and/or prevention of conditions or diseases which are affected by over-activation of signaling in the Wnt pathway and increased presence of nuclear β-catenin. For example, these may be used in preventing and/or retarding proliferation of tumor cells and metastasis, for example carcinomas such as colon carcinomas.
Difluoromaleic anhydride as a source of matrix isolated difluoropropadienone, difluorocyclopropenone and difluoroacetylene
作者:John C. Brahms、William P. Dailey
DOI:10.1021/ja00206a039
日期:1989.11
A 240 nm, reaction de la difluoro-3,4 dihydro-2,5 furannedione-2,5. Obtention de la difluoro-2,3 cyclopropenone, du difluoro acetylene et de la difluoro-3,3 propanedienone
A 240 nm,反应 de la difluoro-3,4 dihydro-2,5 furannedione-2,5。获得 de la difluoro-2,3 cyclopropenone, du difluoroacetylene et de la difluoro-3,3 propanedienone
Synthesis of the first fluorinated cantharidin analogues
作者:Michael Essers、Birgit Wibbeling、Günter Haufe
DOI:10.1016/s0040-4039(01)01056-5
日期:2001.8
time. The key step in each synthesis is an exo-selective Diels–Alder reaction of furan with the appropriate fluorinated maleicanhydride. 17O NMR measurements of 5–7 and the corresponding non-fluorinated parent compounds were undertaken to show the influence of the fluorine substituent(s) on the electronic properties of the oxygen atoms.
Process for the preparation of difluoromaleic anhydride and intermediate
申请人:E. I. Du Pont de Nemours and Company
公开号:US05235069A1
公开(公告)日:1993-08-10
A process for producing difluoromaleic anhydride by reacting sulfur trioxide with a fluorinated precursor selected from the group consisting of hexafluoro-2,5-dihydrofuran, hexafluoro-2,5-dihydrothiophene, difluoro-2,5-dihydrothiophene-2,5-dione and tetrafluoro-2,5-dihydrothiophene-2-one. Also disclosed are the compounds difluoro-2,5-dihydrothiophene-2,5-dione and tetrafluoro-2,5-dihydrothiophene-2-one.