Graduate School of Pharmaceutical Sciences, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Elements Chemistry Laboratory, RIKEN, and Advanced Elements Chemistry Research Team, RIKEN Center for Sustainable Resource Science (CSRS) , 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan.
J Org Chem. 2017 Feb 17;82(4):1931-1935. doi: 10.1021/acs.joc.6b02677. Epub 2017 Jan 27.
Experimental and spectroscopic studies revealed unprecedented reactivity of a "naked" lithium cation with very weakly coordinating anions, including carborane anions. The superactivated lithium cation has greatly enhanced Lewis acidic character and mediates various organic reactions such as carbonyl-ene reaction, NBS-bromination of unactivated aromatics, and Friedel-Crafts alkylation, which are not promoted by conventional lithium salts. Chemical robustness of the counteranion also plays an important role in the chemistry of the strongly activated lithium cation.
实验和光谱研究揭示了“裸露”的锂离子与非常弱配位阴离子(包括硼烷阴离子)前所未有的反应性。超活化的锂离子具有大大增强的路易斯酸性,并介导各种有机反应,如羰基-烯反应、未活化芳环的 NBS 溴化和傅-克烷基化,这些反应不受常规锂盐的促进。抗衡阴离子的化学稳定性在强活化锂离子的化学中也起着重要作用。