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Asymmetric Michael Reactions on Polymeric Support: Auxiliary Immobilization and Stereoselective Construction of Quaternary Stereocenters
Author(s) -
Kreidler Burkard,
Baro Angelika,
Christoffers Jens
Publication year - 2005
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200500450
Subject(s) - chemistry , stereocenter , enamine , transesterification , methyl vinyl ketone , michael reaction , organic chemistry , ketone , organocatalysis , ethylene glycol , yield (engineering) , catalysis , enantioselective synthesis , polymer chemistry , materials science , metallurgy
Several strategies for the immobilization of a L ‐valine‐derived auxiliary on a Merrifield resin and on poly(ethylene glycol) are reported. The latter is shown to work excellently in asymmetric copper( II )‐catalyzed Michael reactions of cyclic β‐oxo esters 2 with methyl vinyl ketone ( 4 ), yielding the corresponding addition products 5 with quaternary stereocenter in selectivities of 97–99 % ee . The PEG‐supported auxiliary 1d can be precipitated from diethyl ether solutions and reused. A sulfur‐containing β‐oxo ester 2c was prepared in 92 % yield by a DMAP‐catalyzed transesterification method in order to detect enamine formation on solid support. The sulfur content can be used as an additional parameter in combustion analysis and therefore, may act as a diagnostic probe for enamine formation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)