Structures of the Reactive Intermediates in Organocatalysis with Diarylprolinol Ethers
作者:Uroš Grošelj、Dieter Seebach、D. Michael Badine、W. Bernd Schweizer、Albert K. Beck、Ingo Krossing、Petra Klose、Yujiro Hayashi、Tadafumi Uchimaru
DOI:10.1002/hlca.200900179
日期:2009.7
Structures of the reactiveintermediates (enamines and iminium ions) of organocatalysis with diarylprolinol derivatives have been determined. To this end, diarylprolinol methyl and silyl ethers, 1, and aldehydes, PhCH2CHO, tBuCH2CHO, PhCH=CHCHO, are condensed to the corresponding enamines, A and 3 (Scheme 2), and cinnamoylidene iminium salts, B and 4 (Scheme 3). These are isolated and fully characterized
The present study reports an asymmetric organocatalytic cascade reaction of 4‐nitroisoxazole derivative with α ,β‐unsaturated aldehydes catalysed by chiral secondary amine. Using this approach, 1,2,3‐trisubstituted cyclopropane products were obtained in isolated yields up to 98% with moderate diastereoselectivities, and enantiopurity up to 99% ee . Moreover, this synthetic protocol can be used for
Mukaiyama–Michael Reactions with Acrolein and Methacrolein: A Catalytic Enantioselective Synthesis of the C17–C28 Fragment of Pectenotoxins
作者:Eeva K. Kemppainen、Gokarneswar Sahoo、Arto Valkonen、Petri M. Pihko
DOI:10.1021/ol203486p
日期:2012.2.17
Enantioselective iminium-catalyzed reactions with acrolein and methacrolein are rare. A catalytic enantioselective Mukaiyama-Michael reaction that readily accepts acrolein or methacrolein as substrates, affording the products in good yields and 91-97% ee, is presented. As an application of the methodology, an enantioselective route to the key C17-C28 segment of the pectenotoxin using the Mukaiyama-Michael reaction as the key step is described.