Pentaphenylcyclopentadienyl ruthenium complexes (3) are excellent catalysts for the racemization of secondary alcohols at ambient temperature. The combination of this process with enzymatic resolution of the alcohols results in a highly efficient synthesis of enantiomericallypure acetates at room temperature with short reaction times for most substrates. This new reaction was applied to a wide range
Studies on Rhizopus arrhizus mediated enantioselective reduction of arylalkanones
作者:Neeta A Salvi、Subrata Chattopadhyay
DOI:10.1016/s0040-4020(01)00134-x
日期:2001.4
The effect of substitution on the biotransformation of various arylalkanones using Rhizopus arrhizus was investigated. The organism was found to be promising for the reduction of phenylalkanones and arylethanones with good to excellent enantioselectivity. The reduction followed Prelog's rule giving the (S)-carbinols in all the cases. The enantioselectivity of the reaction improved with increasing size
Pinane-Type Tridentate Reagents for Enantioselective Reactions: Reduction of Ketones and Addition of Diethylzinc to Aldehydes
作者:Yie-Jia Cherng、Jim-Min Fang、Ta-Jung Lu
DOI:10.1021/jo982403b
日期:1999.4.1
pinane-based diols 5-9 as promoters gave 1-phenylpropanol in favor of the S enantiomer up to 88% ee. Using the pinane-based alcohols 10a-e as promoters, the R enantiomer was obtained as the major product. The addition reactions of diethylzinc to various substituted benzaldehydes, employing the diol ligands 5c and 8e, afforded predominantly the corresponding (S)-alcohols. The chiral modifiers 5-10 were
A new pinane-type tridentate modifier for asymmetric reduction of ketones with lithium aluminum hydride
作者:Yie-Jia Cherng、Jim-Min Fang、Ta-Jung Lu
DOI:10.1016/0957-4166(94)00359-j
日期:1995.1
The reduction of aryl and alkenyl methyl ketones using lithiumaluminumhydride modified with (1R,2S,3S,5R)-(+)-10-anilino-3-ethoxy-2-hydroxypinane (3), afforded chiral secondary alcohols in 83–96% yields and 53–97% optical yields. The modifier 3 was prepared from (1R)-(−)-myrtenol and was readily recovered (>96%) after reduction. The reduction of acetophenone in the presence of lithium iodide gave
Asymmetric reduction of ketones with sodium aluminum hydride modified by various chiral diols
作者:M. G. Vinogradov、L. S. Gorshkova、V. A. Pavlov、O. V. Mikhalev、G. V. Chel'tsova、I. V. Razmanov、V. A. Ferapontov、O. R. Malyshev、G. L. Heise
DOI:10.1007/bf02494775
日期:2000.3
modified NaAlH4 was considerably higher than that of 1,2-diols. The effect of the nature of the achiral ligand additionally introduced into the chiral hydride reagent on the enantioselectivity of ketone reduction was studied. It was proposed that the sodium cation does not necessarily participate at the stage governing the reaction stereochemistry.