- Asymmetric hydrosilylation of ketones using trans-chelating chiral peralkylbisphosphine ligands bearing primary alkyl substituents on phosphorus atoms
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Asymmetric hydrosilylation of simple ketones with diphenylsilane proceeded at -40 °C in the presence of a rhodium complex (0.001 - 0.01 molar amount) coordinated with a trans-chelating chiral bisphosphine ligand bearing linear alkyl substituents on the phosphorus atoms, (R,R)-(S,S)-Et-, Pr-, or BuTRAP, giving the corresponding optically active (S)- secondary alcohols with up to 97% ee. The asymmetric hydrosilylation using TRAP ligands with bulkier P-substituents resulted in much lower enantioselectivities. The EtTRAP-rhodium catalyst was also effective for asymmetric hydrosilylation of keto esters with a coordination site for a rhodium atom (up to 98% ee). Optically active symmetrical diols were obtained with up to 99% ee from the corresponding diketones via the asymmetric reduction using 2.5 molar amounts of diphenylsilane.
- Kuwano, Ryoichi,Sawamura, Masaya,Shirai, Junya,Takahashi, Masatoshi,Ito, Yoshihiko
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p. 485 - 496
(2007/10/03)
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- Lactols in Stereoselection 1. Highly selective 1,4- and 1,5-Asymmetric Induction
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Nucleophilic addition to substituted γ- and δ-lactols with titanium reagents provides 1,4-syn and 1,5-syn diols in high stereoselectivity, which represents a new and simple method for the remote asymmetric induction.
- Tomooka, Katsuhiko,Okinaga, Tatsuyuki,Suzuki, Keisuke,Tsuchihashi, Gen-ichi
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p. 6335 - 6338
(2007/10/02)
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