Copper-Promoted Coupling of Carbon Dioxide and Propargylic Alcohols: Expansion of Substrate Scope and Trapping of Vinyl Copper Intermediate

We have successfully demonstrated that in the presence of N,N-diisopropylethylamine, copper iodide could efficiently catalyze the coupling of internal propargylic alcohols with carbon dioxide to afford the corresponding -alkylidene cyclic carbonates in moderate to excellent yields. Moreover, we have developed a new and versatile protocol for the chemo- and stereoselective synthesis of a wide range of (E)--iodoalkylidene cyclic carbonates from carbon dioxide, propargylic alcohols and potassium iodide using copper salt as the promoter. The process is proposed to proceed through the trapping of the vinyl copper intermediate by in situ generated triiodide ion as electrophile.