872692-21-2Relevant articles and documents
Asymmetric michael reactions on polymeric support: Auxiliary immobilization and stereoselective construction of quaternary stereocenters
Kreidler, Burkard,Baro, Angelika,Christoffers, Jens
, p. 5339 - 5348 (2007/10/03)
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, 2005.