Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, 81377 München (Germany) http://www.cup.uni-muenchen.de/oc/mayr/
Angew Chem Int Ed Engl. 2015 Feb 23;54(9):2780-3. doi: 10.1002/anie.201410562. Epub 2015 Jan 21.
Boron ate complexes derived from thienyl and furyl boronic esters and aryllithium compounds have been isolated and characterized by X-ray crystallography. Products and mechanisms of their reactions with carbenium and iminium ions have been analyzed. Kinetics of these reactions were monitored by UV/Vis spectroscopy, and the influence of the aryl substituents, the diol ligands (pinacol, ethylene glycol, neopentyl glycol, catechol), and the counterions on the nucleophilic reactivity of the boron ate complexes were examined. A Hammett correlation confirmed the polar nature of their reactions with benzhydrylium ions, and the correlation lg k(20 °C)=sN (E+N) was employed to determine the nucleophilicities of the boron ate complexes and to compare them with those of other borates and boronates. The neopentyl and ethylene glycol derivatives were found to be 10(4) times more reactive than the pinacol and catechol derivatives.
噻吩基和呋喃基硼酸酯与芳基锂化合物衍生的硼酸盐配合物已通过 X 射线晶体学方法进行了分离和表征。分析了它们与碳正离子和亚胺离子的反应产物和反应机理。通过紫外/可见光谱监测了这些反应的动力学，并考察了芳基取代基、二醇配体（频哪醇、乙二醇、新戊二醇、儿茶酚）和抗衡离子对硼酸盐配合物亲核反应性的影响。Hammett 相关证实了它们与苄基鎓离子反应的极性性质，并用 lg k(20 °C)=sN (E+N) 相关式来确定硼酸盐配合物的亲核性，并将其与其他硼酸酯和硼酸盐进行比较。发现新戊二醇和乙二醇衍生物比频哪醇和儿茶酚衍生物的反应性高 10(4) 倍。
