Laboratoire BioCIS-CNRS, Faculté de Pharmacie, Univ. Paris Sud, 5 rue Jean-Baptiste Clément, F-92296 Châtenay-Malabry, France.
J Org Chem. 2011 Feb 18;76(4):1126-33. doi: 10.1021/jo1023816. Epub 2011 Jan 18.
The influence of substituents on the properties of tri- and hexafluorinated alcohols derived from 2,2,2-trifluoroethanol (TFE) and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) was examined. Measurements of specific solvent-solute interactions revealed that H-bond donation (HBD) of fluorinated alcohols is sensitive to the steric hindrance of the OH group, whereas their Brønsted acidity is dependent only on the number of fluorine atoms. For hexafluorinated alcohols (HFAs), their association with amines characterized by X-ray diffraction showed that the balance between HBD and acidity is influenced by their structure. Moreover, the ability of HFAs to donate H-bonds is exerted in synclinal (sc), synperiplanar (sp), and also antiperiplanar (ap) conformations along the C-O bond. Comparison of the effects of fluorinated alcohols as promoting solvents in three reactions is reported. The positive correlation between rate constants and H-bonding donation ability for sulfide oxidation and imino Diels-Alder reaction brings to light the role of this property, while acidity might have a minor influence. In the third reaction, epoxide opening by piperidine, none of these properties can clearly be put forward at this stage.
研究了取代基对由 2,2,2-三氟乙醇 (TFE) 和 1,1,1,3,3,3-六氟-2-丙醇 (HFIP) 衍生的三氟和六氟醇性质的影响。特定溶剂-溶质相互作用的测量表明，氟化醇的 H 键供体 (HBD) 对 OH 基团的空间位阻敏感，而其布朗斯台德酸度仅取决于氟原子的数量。对于六氟醇 (HFAs)，与胺的 X 射线衍射研究表明，其 HBD 和酸度之间的平衡受其结构影响。此外，HFAs 沿 C-O 键在顺式 (sc)、顺式平行 (sp) 和反式平行 (ap) 构象中发挥氢键供体的能力。报告了三氟醇作为促进溶剂在三种反应中的应用效果比较。硫化物氧化和亚胺 Diels-Alder 反应的速率常数与氢键供体能力之间的正相关性揭示了这一性质的作用，而酸度可能影响较小。在第三种反应中，哌啶开环的环氧，目前在这一阶段还不能清楚地提出这些性质中的任何一个。
