Alkoxydienes via Copper-Promoted Couplings: Utilizing an Alkyne Effect

Simple alkenes and alkynes, with 3-hexyne in particular, are found to be important pi ligands for oxidative copper-based coupling (modern Ullmann) reactions. This enabled syntheses of various alkoxydienes with removable protecting groups that are valuable substrates for Diets-Alder reactions from alcohols and vinyl boronate esters. In addition to demonstrating that 3-hexyne is a ligand for copper in both stoichiometric and catalytic reactions, the reaction atmosphere was found to play a critical role.