Quadruple Borylation of Terminal Alkynes
Daiki Yukimori1, Yuki Nagashima1, Chao Wang1
1Graduate School of Pharmaceutical Sciences , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku, Tokyo 113-0033 , Japan.
Journal of the American Chemical Society
|June 13, 2019
Abstract:
We present the first quadruple borylation reaction of terminal alkynes, affording functionalized 1,1,2,2-tetrakis(boronate) derivatives in a chemo-/regioselective manner. The methodology is operationally simple and a novel B-B bond activation without the need for a transition-metal catalyst.
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The acidic strength of hydrocarbons follows the order: Alkynes > Alkenes > Alkanes. The strength of an acid is commonly expressed in units of pKa — the lower the pKa, the stronger the acid. Among the hydrocarbons, terminal alkynes have lower pKa values and are, therefore, more acidic. For example, the pKa values for ethane, ethene, and acetylene are 51, 44, and 25, respectively, as shown here.
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