Martínez-Aguirre Mayte A, Yatsimirsky Anatoly K
Facultad de Química, Universidad Nacional Autónoma de México, 04510 México, D.F., México.
J Org Chem. 2015 May 15;80(10):4985-93. doi: 10.1021/acs.joc.5b00377. Epub 2015 May 1.
Interactions between arylboronic acids and a series of anions as tetrabutylammonium salts in DMSO and MeCN were studied by (1)H and (11)B NMR as well as spectrophotometrically. Boronic acids act as Brønsted acid type receptors through hydrogen bonding with B(OH)2 hydroxyl groups toward Cl(-), Br(-), HSO4(-), and AcO(-), but they act as Lewis acid type receptors toward F(-) and H2PO4(-), which form tetrahedral adducts with the B(III) center of boronic acids, although there is also evidence for some contribution of hydrogen bonding with these anions. The Hammett plot for the binding constants of AcO(-) with 3- and 4-substituted phenylboronic acids in DMSO is nonlinear, with a small negative slope for electron-donating and weakly electron-accepting substituents and a large positive slope for strongly electron-accepting substituents. 3-Nitrophenylboronic acid recognizes zwitterions of amino acids in DMSO, and its UV absorption maximum undergoes a significant red shift in the presence of acetate anions, providing a means for sensing anions optically. Arylboronic acids as Brønsted acid type receptors show relatively low sensitivity to solvent polarity and are equally or even more efficient than widely employed proton donors such as ureas or dicarboxamides.
通过¹H和¹¹B核磁共振以及分光光度法研究了芳基硼酸与一系列作为四丁基铵盐的阴离子在二甲亚砜（DMSO）和乙腈（MeCN）中的相互作用。硼酸通过与B(OH)₂羟基形成氢键，对Cl⁻、Br⁻、HSO₄⁻和AcO⁻起到布朗斯特酸型受体的作用，但对F⁻和H₂PO₄⁻起到路易斯酸型受体的作用，它们与硼酸的B(III)中心形成四面体加合物，不过也有证据表明与这些阴离子存在一些氢键作用。在DMSO中，AcO⁻与3-和4-取代苯基硼酸结合常数的哈米特图是非线性的，给电子和弱吸电子取代基的斜率为小的负值，强吸电子取代基的斜率为大的正值。3-硝基苯基硼酸在DMSO中能识别氨基酸的两性离子，在醋酸根阴离子存在下其紫外吸收最大值发生显著红移，提供了一种光学传感阴离子的方法。作为布朗斯特酸型受体的芳基硼酸对溶剂极性的敏感性相对较低，并且比广泛使用的质子供体如脲或二羧酰胺同样有效甚至更有效。
