Unusual Carbon-Carbon Bond Formations between Allylboronates and Acetals or Ketals Catalyzed by a Peculiar Indium(I) Lewis Acid
Uwe Schneider, Hai T. Dao and Shū Kobayashi*
*Department of Chemistry, School of Science and Graduate School of Pharmaceutical Sciences, The University of Tokyo, The HFRE Division, ERATO, JST, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan, Email: shu_kobayashichem.s.u-tokyo.ac.jp
U. Schneider, H. T. Dao, S. Kobayashi, Org. Lett., 2010, 12, 2488-2491.
DOI: 10.1021/ol100450s (free Supporting Information)
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InOTf is as an effective Lewis acid catalyst for unprecedented nucleophilic substitution of acetals with allylboronates. A transmetalative SN1 mechanism is proposed in which a single InI center acts as a dual catalyst to activate both reagents sequentially. Contrary to the classic γ-selectivity of allylsilanes (Hosomi-Sakurai reaction), this InI-catalyzed borono variant displays distinct α-selectivity.
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