Synthesis of allenylboronic acids and allenylboronates
A copper-catalyzed synthesis of benzyl-, allyl-, and allenyl-boronates from benzylic, allylic, and propargylic alcohols, respectively, exhibits a broad reaction scope and high efficiency under mild conditions. Preliminarily mechanistic studies suggest that nucleophilic substitution is involved in this reaction.
L. Mao, K. J. Szabó, T. B. Marder, Org. Lett., 2017, 19, 1204-1207.
Bimetallic Pd/Cu and Pd/Ag catalytic systems enable a stererospecifically borylation of propargylic alcohol derivatives via formal SN2′ pathways to give allenyl boronates. Opening of propargyl epoxides leads to 1,2-diborylated butadienes probably via en allenylboronate intermediate.
T. S. N. Zhao, Y. Yang, T. Lessing, K. J. Szabo, J. Am. Chem. Soc., 2014, 136, 7359-7542.
A Cu(O-t-Bu)-Xantphos catalyst system was effective for the preparation of various allenylboronates with different substitution patterns, those with functional groups, and an axially chiral one. A Lewis acid promoted stereoselective addition of allenylboronates to aldehydes leads to homopropargylic alcohols.
H. Ito, Y. Sasaki, M. Sawamura, J. Am. Chem. Soc., 2008, 130, 15774-15775.