Ligand-Promoted, Boron-Mediated Chemoselective Carboxylic Acid Aldol Reaction
Hideoki Nagai, Yuya Morita, Yohei Shimizu* and Motomu Kanai*
*Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan, Email: y-shimizumol.f.u-tokyo.ac.jp, kanaimol.f.u-ac.tokyo.ac.jp
H. Nagai, Y. Morita, Y. Shimizu, M. Kanai, Org. Lett., 2016, 18, 2276-2279.
DOI: 10.1021/acs.orglett.6b00914 (free Supporting Information)
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Boron compounds and a mild organic base (DBU) mediate a carboxylic acid selective aldol reaction. Electron-withdrawing groups in amino acid derivative ligands reacted with BH3ĚSMe2 forms a boron promoter with increased Lewis acidity at the boron atom, which facilitated the carboxylic acid selective enolate formation. The reaction tolerates other carbonyl groups such as amides, esters, ketones, or aliphatic aldehydes.
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