Design of New Chiral Phase-Transfer Catalysts with Dual Functions for Highly Enantioselective Epoxidation of α,β-Unsaturated Ketones
Takashi Ooi, Daisuke Ohara, Masazumi Tamura and Keiji Maruoka*
*Department of Chemistry, Graduate School of Science, Kyoto University,
Sakyo, Kyoto 606-8502, Japan, Email: maruoka
kuchem.kyoto-u.ac.jp
T. Ooi, D. Ohara, M. Tamura, K. Maruoka, J. Am. Chem. Soc., 2004, 126, 6844-6845.
DOI: 10.1021/ja048600b
Abstract
Promising, dual-functioning chiral catalysts for the highly enantioselective epoxidation of α,β-unsaturated ketones gave epoxy chalcones in excelllent yield and high enantioselectivity using 13% NaOCl as oxidizing agent in toluene under mild phase-transfer conditions.
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Details
The document details the development of new chiral phase-transfer catalysts for the enantioselective epoxidation of α,β-unsaturated ketones by researchers Takashi Ooi, Daisuke Ohara, Masazumi Tamura, and Keiji Maruoka at Kyoto University. The team introduced a novel chiral quaternary ammonium bromide catalyst with dual functions, designed to enhance reactivity and enantioselectivity through hydrogen-bonding interactions with prochiral enones. The catalyst 1e, featuring a flexible biphenyl subunit and a diphenylhydroxymethyl substituent, demonstrated remarkable efficiency, achieving a 99% yield and 96% enantiomeric excess in the epoxidation of chalcone derivatives. Structural analysis via X-ray diffraction revealed a unique three-dimensional architecture that facilitates precise positioning of reactants, leading to high enantiofacial differentiation. The study confirmed the catalyst's broad applicability across various α,β-unsaturated ketones, consistently delivering high yields and enantiomeric purity under mild conditions. This innovative approach offers significant advantages, including operational simplicity, environmental consciousness, and the potential for further development in asymmetric phase-transfer reactions. The research was supported by the Kurata Memorial Hitachi Science and Technology Foundation and the Japanese Ministry of Education, Culture, Sports, Science, and Technology, highlighting its importance and potential impact on synthetic chemistry.
Key Words
Epoxidation, Organocatalysis, Sodium Hypochlorite
ID: J48-Y2004-1490
