The first enantioselective direct aldol addition of N-Boc-oxindoles to polymeric ethyl glyoxylate is presented. The reaction is performed by using as low as 0.1 mol% (DHQ)2PHAL and gives access to α- hydroxycarboxylate derivatives bearing adjacent secondary alcohol and quaternary stereocenters with high levels of diastereo- and enantiocontrol. The use of ethyl glyoxylate in its polymeric form represents an important advantage for synthetic applications and allows us to directly install a C2 unit ready to be converted in useful building blocks. A further one-pot protection/deprotection sequence catalyzed by Zn(ClO4) 2·6 H2O preserved the α-hydroxycarboxylates from racemization by means of a parasitic alcohol-catalyzed retroaldol reaction. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cinchona alkaloid-catalyzed enantioselective direct aldol reaction of N-Boc-oxindoles with polymeric ethyl glyoxylate

Pesciaioli F.;Mancinelli M.;
2011

Abstract

The first enantioselective direct aldol addition of N-Boc-oxindoles to polymeric ethyl glyoxylate is presented. The reaction is performed by using as low as 0.1 mol% (DHQ)2PHAL and gives access to α- hydroxycarboxylate derivatives bearing adjacent secondary alcohol and quaternary stereocenters with high levels of diastereo- and enantiocontrol. The use of ethyl glyoxylate in its polymeric form represents an important advantage for synthetic applications and allows us to directly install a C2 unit ready to be converted in useful building blocks. A further one-pot protection/deprotection sequence catalyzed by Zn(ClO4) 2·6 H2O preserved the α-hydroxycarboxylates from racemization by means of a parasitic alcohol-catalyzed retroaldol reaction. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11697/150179
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