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Organocatalytic Enantioselective Cascade Michael-Alkylation Reactions: Synthesis of Chiral Cyclopropanes and Investigation of Unexpected Organocatalyzed Stereoselective Ring Opening of Cyclopropanes

Hexin Xie, Liansuo Zu, Hao Li, Jian Wang and Wei Wang*

*Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131-0001, Email: wwangunm.edu

H. Xie, L. Zu, H. Li, J. Wang, W. Wang, J. Am. Chem. Soc., 2007, 129, 10886-10894.

DOI: 10.1021/ja073262a (free Supporting Information)


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Abstract

An organocatalytic asymmetric cascade Michael reaction of α,β-unsaturated aldehydes with bromomalonates, efficiently catalyzed by chiral diphenylprolinol TMS ether in the presence of base 2,6-lutidine, gives cyclopropanes in high enantio- and diastereoselectivities. Using NaOAc as base, a spontaneous ring-opening of cyclopropanes leads to (E) α-substituted malonate α,β-unsaturated aldehydes.

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proposed mechanism



Key Words

Organocatalysis, Cyclopropanes, Active Methylenes


ID: J48-Y2007-2950