A novel D 2 -symmetrical chiral tetraoxazoline ligand was synthesized from 1,2,4,5-benzenetetracarboxylic acid and l-valinol via a one-pot reaction, and the asymmetric hydrosilylation of aromatic ketones was carried out in dichloromethane in the presence of 1.0 mol% of a bivalent copper ion catalyst with the tetraoxazoline to give optically active secondary alcohols. The chiral catalyst showed excellent activities and enantioselectivities in the hydrosilylation of aryl ketones with up to 99% ee.
SummarySeven polyoxazoline ligands were synthesized in high yield in a one-pot reaction by heating polycarboxylic acids or their esters and chiral β-amino alcohols under reflux with concomitant removal of water or the alcohol produced in the reaction. The method is much simpler and more efficient in comparison to those methods reported in the literature.The compounds were used as chiral ligands in the rhodium-catalyzed asymmetric hydrosilylation of aromatic ketones, and the effects of the linkers and the substituents present on the oxazoline rings on the yield and enantioselectivity investigated. Compound 2 was identified as the best ligand of this family for the hydrosilylation of aromatic ketones.
A Facile and Efficient Synthesis of Bis(oxazoline)s -[via reaction of dicarboxylic acids with β-amino alcohols]. -(LI*, W. J.; QIU, S. X.; J. Heterocycl. Chem. 47 (2010) 6, 1340-1343, http://dx.
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