Single-Isomer Tetrasubstituted Olefins from Regioselective and Stereospecific Palladium-Catalyzed Coupling of β-Chloro-α-iodo-α,β-unsaturated Esters
Alison B. Lemay, Katarina S. Vulic and William W. Ogilvie*
*Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa,
Ontario, Canada K1N 6N5, Email: wogilviescience.uottawa.ca
A. B. Lemay, K. S. Vulic, W. W. Ogilvie, J. Org. Chem., 2006, 71, 3615-3618.
DOI: 10.1021/jo060144h
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Abstract
2-Alkynyl esters are stereo- and regioselectively converted to E-β-chloro-α-iodo-α,β-unsaturated esters by exposure to Bu4NI in refluxing dichloroethane. Single-isomer tetrasubstituted olefins bearing four different carbon substituents are then synthesized by sequential palladium-catalyzed coupling reactions.
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Details
The document describes a method for the efficient regioselective and stereospecific synthesis of tetrasubstituted olefins. The process begins with the conversion of 2-alkynyl esters to E-β-chloro-α-iodo-α,β-unsaturated esters using Bu4NI in refluxing dichloroethane. These intermediates are then subjected to sequential palladium-catalyzed coupling reactions to produce single-isomer tetrasubstituted olefins with four different carbon substituents. The method is noted for its simplicity, high yields, and selectivity, overcoming challenges associated with steric hindrance and lack of directing substituents. The stereochemistry of the products is confirmed using NMR analysis. The process is scalable and compatible with various functional groups, making it a valuable tool for synthesizing complex olefins used in natural products and pharmaceuticals. The study highlights the superiority of Bu4NI over ICl for the initial conversion step, providing cleaner reactions and higher yields. The document also includes detailed experimental procedures and characterization data for the synthesized compounds. The research is supported by various Canadian institutions and aims to expand the scope of this methodology for further applications in asymmetric transformations.
Key Words
Vinyliodides, Vinylchlorides, Enynes, Sonogashira Coupling, Suzuki Coupling, 1,3-dienes
ID: J42-Y2006-1170