Murata Yukihiro, Matsunagi Kenta, Kashida Junki, Shoji Yoshiaki, Özen Cihan, Maeda Satoshi, Fukushima Takanori
Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, 226-8503, Japan.
Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, 226-8502, Japan.
Angew Chem Int Ed Engl. 2021 Jun 21;60(26):14630-14635. doi: 10.1002/anie.202103512. Epub 2021 May 19.
While attractive interactions between borane and olefin have been postulated to trigger various boron-mediated organic transformations, proximity structures of these functional groups, other than the formation of weak van der Waals complexes, have never been directly observed. Here we show that a close intramolecular borane-olefin interaction operates in macrocyclic systems containing borane and olefinic groups obtained by multi-step 1,2-carboboration between a strained alkyne and 9-borafluorene derivatives. Depending on Lewis acidity of the borane moiety and the size of the macrocycles, the magnitude of interaction changes, resulting in different reaction modes. The whole picture of the multi-step reactions has been revealed experimentally with theoretical supports. The present finding may not only provide a deeper understanding of the fundamental boron-mediated interaction but also lead to the development of new organic transformations involving molecular activation by boranes.
虽然已经假定硼烷与烯烃之间的吸引相互作用会引发各种硼介导的有机转化，但除了形成弱范德华络合物之外，这些官能团的接近结构从未被直接观察到。在此我们表明，在通过张力炔烃与9-硼芴衍生物之间的多步1,2-碳硼化反应得到的含有硼烷和烯烃基团的大环体系中，存在紧密的分子内硼烷-烯烃相互作用。根据硼烷部分的路易斯酸度和大环的大小，相互作用的强度会发生变化，从而导致不同的反应模式。通过理论支持，实验揭示了多步反应的全貌。这一发现不仅可以更深入地理解基本的硼介导相互作用，还可能导致开发涉及硼烷分子活化的新有机转化反应。
