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Title: Effect of substituents on enantioselectivity in chiral oxazaborolidine mediated asymmetric ketone reduction reaction
Authors: Balakrishnan, U
Ananthi, N
Velmathi, S
Keywords: L-Valine;Prochiral ketone reduction;Oxazaborolidine;Chiral amines;Asymmetric synthesis
Issue Date: Sep-2011
Publisher: NISCAIR-CSIR, India
Abstract: Various new chiral ligands have been synthesized by the condensation of different esters of l-Valine with different substituted salicylaldehydes in order to find the most effective catalyst for the enantioselctive ketone reduction. Chiral amine synthesized from l-Valine methyl ester and 5-chloro salicylaldehyde is found to catalyse the enantioselective reduction of prochiral ketone with high yield (99%) and enantiomeric excess (91%) with 20 mol% of the catalyst using borane dimethylsulphide as a stoichiometric reducutant. Different subsituted prochiral ketones have also been reduced in high yield upto 90% and the corresponding secondary alcohols are formed with good enantiomeric excess upto 99%. The mechanism of this reduction can be very well explained by considering a plausible mechanism for the CBS catalyst.
Page(s): 1157-1164
ISSN: 0975-0983(Online); 0376-4699(Print)
Appears in Collections:IJC-B Vol.50B(09) [September 2011]

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