American Chemical Society
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Lewis Base Activation of Lewis Acids: Group 13. In Situ Generation and Reaction of Borenium Ions

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journal contribution
posted on 2013-11-25, 00:00 authored by Scott E. Denmark, Yusuke Ueki
A variety of Lewis bases were combined with 9-BBN-NTf2 to establish the requirements for the generation of borenium cations. Five different types of behaviors were found, but the most interesting was the combination of Et3N, DABCO, 2,6-lutidine, or Ph3PS, which formed borenium ions exclusively even in sub- or superstoichiometric quantities. The 9-BBN borenium ion complex of 2,6-lutidine rapidly catalyzes the hydrosilylation of a variety of ketones in the presence of Et3SiH. Preliminary mechanistic experiments suggest that the reduction involves borenium ion activation of Et3SiH and not the ketone.