M. Omote, Y. Nishimura, Kazuyuki Sato
2006
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0
Influential Citations
2
Citations
Journal
Journal of Fluorine Chemistry
Abstract
Abstract ( R a)-( R ) 2 -2,2′-Bis(1-hydroxy-1H-perfluorooctyl)biphenyl (( R a)-( R ) 2 - 1c ), which is an axially dissymmetric ligand with two chiral centers, works as a good chiral auxiliary for asymmetric aldol reaction. Thus, the reaction of monopropanoyl ester of 1c ( 2 ) with benzaldehyde in the presence of triethylamine and titanium(IV) chloride gave (2 R ),(3 S )- and (2 R ),(3 R )-3-hydroxy-2-methyl-3-phenylpropanoic acid esters ( 3a ) in an approximate ratio of 4:1 in a total high yield. This result shows that stereoselectivity at 2-position is quite high, while that at 3-position is moderate. Both isomers were easily separated by column chromatography. Methanolysis of the separated isomers gave nearly quantitative recovery of 1c by extraction with a fluorous solvent without any loss of ee, while methyl (2 R ),(3 S )- or (2 R ),(3 R )-3-hydroxy-2-methyl-3-phenylpropanoates were obtained by CH 2 Cl 2 extraction quantitatively in >99% ee. Aldol reaction of 2 with various aldehydes gave similar results.