Single-Isomer Tetrasubstituted Olefins from Regioselective and Stereospecific Palladium-Catalyzed Coupling of beta- Chloro-alpha-iodo-alpha,beta-unsaturated Esters

摘要

The efficient regioselective and Stereospecific synthesis of tetrasubstituted olefins using a mild and convenient method is disclosed.2-Alkynyl esters are selectively converted to E-beta-chloro-alpha-iodo-alpha,beta-unsaturated esters by exposure to Bu_4-NI in refluxing dichloroethane.These products are produced cleanly,regio- and stereoselectively,and in high yields.Single-isomer tetrasubstituted olefins bearing four different carbon substituents are then synthesized by sequential palladium-catalyzed coupling reactions.Selectivity results from reactivity differences in the intermediate substrates.