BINAP/AgOTf/KF/18-Crown-6 as New Bifunctional Catalysts for Asymmetric Sakurai-Hosomi Allylation and Mukaiyama Aldol Reaction
Manabu Wadamoto, Nobuko Ozasa, Akira Yanagisawa and Hisashi Yamamoto*
*Department of Chemistry, The University of Chicago, 5735
South Ellis Avenue, Chicago, IL 60637, Email: yamamoto
uchicago.edu
M. Wadamoto, N. Ozasa, A. Yanagisawa, H. Yamamoto, J. Org. Chem., 2003, 68, 5593-5601.
DOI: 10.1021/jo020691c
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Abstract
A complex of 18-crown-6 and KF is effective as a soluble fluoride source to activate asymmetric Sakurai-Hosomi allylations and asymmetric Mukaiyama-type aldol reactions using BINAP and silver(I) triflate as catalyst. Allylations and aldol reactions give products in high yields and remarkable enantioselectivities.
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Details
The document discusses the development of a new bifunctional catalyst system comprising BINAP, AgOTf, KF, and 18-crown-6 for asymmetric Sakurai-Hosomi allylation and Mukaiyama aldol reactions. This catalyst system effectively activates allylic trimethoxysilanes and trimethoxysilyl enol ethers, leading to high yields and remarkable enantioselectivities in the formation of homoallylic alcohols and β-hydroxy carbonyl compounds. The study highlights the advantages of using less toxic trimethoxysilyl compounds over traditional trialkyltin compounds. The optimal conditions involve using THF as the solvent at -20°C, with the catalyst system showing high anti selectivity for E-silyl enol ethers and syn selectivity for Z-silyl enol ethers. The research also explores the effects of various ligands, solvents, and reaction temperatures on the yield and enantioselectivity. The findings suggest that the mixed catalysts act as bifunctional chiral catalysts, providing an environmentally friendlier approach to these important organic reactions. The document concludes with detailed experimental procedures and spectral data for the synthesized compounds, emphasizing the potential of this catalyst system in asymmetric synthesis.
Silver-Catalyzed Asymmetric Sakurai-Hosomi Allylation of Ketones
M. Wadamoto, H. Yamamoto, J. Am. Chem. Soc., 2005, 127, 14556-14557.
K. Ishihara, S. Kondo, H. Yamamoto, J. Org. Chem., 2000, 65, 9125-9128.
Key Words
Hosomi-Sakurai Reaction, Mukaiyama Aldol Addition
ID: J42-Y2003-560
