PhCH=P(MeNCH2CH2)3N: A Novel Ylide for Quantitative E Selectivity in the Wittig Reaction
Zhigang Wang, Guangtao Zhang, Ilia Guzei and John G. Verkade*
*Department of Chemistry, Iowa State University, Ames, Iowa 50011-3111,
Email: jverkadeiastate.edu
Z. Wang, G. Zhang, I. Guzei, J. G. Verkade, J. Org. Chem., 2001, 66, 3521-3524.
DOI: 10.1021/jo0100704
see article for more reactions
Abstract
The semi-stabilized ylide PhCH=P(MeNCH2CH2)3N, which is readily prepared from the commercially available base P(MeNCH2CH2)3N, reacts with aldehydes to give alkenes in high yield with quantitative E selectivity. The E selectivity is discussed.
see article for more examples
proposed intermediates
Details
The document discusses the synthesis and application of a novel semi-stabilized ylide, PhCHP(MeNCH2CH2)3N (1), in the Wittig reaction to achieve high yields of alkenes with quantitative E selectivity. This ylide is derived from the commercially available nonionic base P(MeNCH2CH2)3N and reacts with various aldehydes to produce E-alkenes consistently, regardless of changes in metal ion, temperature, or solvent polarity. The study contrasts this ylide's performance with other ylides, noting that traditional ylides often yield mixtures of E and Z isomers. The authors attribute the exclusive E selectivity to the unique tricyclic structure of ylide 1, which minimizes 1,3-interactions and favors the formation of trans-oxaphosphetane intermediates. The document includes detailed experimental procedures, reaction conditions, and results, highlighting the influence of different bases and solvents on the reaction outcomes. The findings support the Vedejs model of Wittig reaction stereochemistry and suggest that the rigid structure of ylide 1 plays a crucial role in its high stereoselectivity. The research was supported by the Petroleum Research Fund and the National Science Foundation.
Key Words
ID: J42-Y2001-130