Palladium0-catalyzed isomerization of (Z)-1-functionalized-4-acetoxy-2-butenes: Solvent and substituent effects

The Pd(PPh3)4-catalyzed isomerization of (Z)-1,4-diacetoxy-2-butene, (Z)-1-(t-butyldimethylsilyloxy)-4-acetoxy-2-butene and (Z)-1-(t-butyldiphenylsilyloxy)-4-acetoxy-2-butene affords the corresponding (E)-isomers and 1,2-difunctionalized-3-butenes. In THF, the formation of the (E)-isomers is mainly due to reaction from an η1-allylpalladium intermediate while an η3-allylpalladium is the main key intermediate in DMF. The time to reach equilibrium between the products and their respective concentrations depend on the nature of the substituents and the solvent.

The mechanism of the isomerization of the substrate is solvent dependent. The time to reach equilibrium between the three compounds, and their respective concentrations depend on the nature of Y and solvent.Figure optionsDownload as PowerPoint slide