An Insoluble Copper(II) Acetylacetonate–Chiral Bipyridine Complex that Catalyzes Asymmetric Silyl Conjugate Addition in Water
投稿者:
Unknown
Taku Kitanosono, Lei Zhu, Chang Liu, Pengyu Xu, and Shu̅ Kobayashi*
Taku Kitanosono
Department of Chemistry, School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
J. Am. Chem. Soc., Article ASAP
DOI: 10.1021/jacs.5b11418
Publication Date (Web): December 8, 2015
Copyright © 2015 American Chemical Society
Department of Chemistry, School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
J. Am. Chem. Soc., Article ASAP
DOI: 10.1021/jacs.5b11418
Publication Date (Web): December 8, 2015
Copyright © 2015 American Chemical Society
Abstract
Acicular purplish crystals were obtained from Cu(acac)2 and a chiral bipyridine ligand. Although the crystals were not soluble, they nevertheless catalyzed asymmetric silyl conjugate addition of lipophilic substrates in water. Indeed, the reactions proceeded efficiently only in water; they did not proceed well either in organic solvents or in mixed water/organic solvents in which the catalyst/substrates were soluble. This is in pronounced contrast to conventional organic reactions wherein the catalyst/substrates tend to be in solution. Several advantages of the chiral Cu(II) catalysis in water over previously reported catalyst systems have been demonstrated. Water is expected to play a prominent role in constructing and stabilizing sterically confined transition states and accelerating subsequent protonation to achieve high yields and enantioselectivities.
Acicular purplish crystals were obtained from Cu(acac)2 and a chiral bipyridine ligand. Although the crystals were not soluble, they nevertheless catalyzed asymmetric silyl conjugate addition of lipophilic substrates in water. Indeed, the reactions proceeded efficiently only in water; they did not proceed well either in organic solvents or in mixed water/organic solvents in which the catalyst/substrates were soluble. This is in pronounced contrast to conventional organic reactions wherein the catalyst/substrates tend to be in solution. Several advantages of the chiral Cu(II) catalysis in water over previously reported catalyst systems have been demonstrated. Water is expected to play a prominent role in constructing and stabilizing sterically confined transition states and accelerating subsequent protonation to achieve high yields and enantioselectivities.
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