Subscribe to RSS
DOI: 10.1055/s-0030-1258782
Asymmetric Direct Henry Reaction of Ynals Catalyzed by Iminophosphorane
Contributor(s):Benjamin List, Ji-Woong LeeNagoya University, Japan
Catalytic Asymmetric Direct Henry Reaction of Ynals: Short Syntheses of (2S,3R)-(+)-Xestoaminol C and (-)-Codonopsinines
Angew. Chem. Int. Ed. 2010, 49: 7562-7565
Publication History
Publication Date:
21 October 2010 (online)
Key words
Henry reaction - phosphonium salts - 1,2-amino alcohols - ynals
Significance
In this report, the authors present a direct asymmetric Henry reaction of ynals. The products, various propargylic alcohols, were obtained in high enantiopurity (er up to 99.5:0.5) by using the tetraaminophosphonium salt 1 as a pre-catalyst. Interestingly, the concentration of DMF is crucial for a reasonable conversion into the desired products. The authors observed a tetraaminophosphonium cation complex with alkoxide, which should be generated during the course of the reaction and can deactivate the cation.
Comment
Ooi and co-workers nicely applied their previously introduced iminophosphorane catalysis (J. Am. Chem. Soc. 2007, 129, 12392) for the direct Henry reaction of ynals to produce optically active anti-β-nitro propargylic alcohols. The obtained Henry adducts could be easily transformed into various biologically active compounds, such as xestoaminol C and codonopsinines. The observed effect of DMF concentration could be ascribed to a proper dissociation of the catalyst nitro group complex by DMF.