Copper‐Catalysed Rearrangement of Cyclic Ethynylethylene Carbonates: Synthetic Applications and Mechanistic Studies

Abstract

AbstractTransition‐metal‐catalysed reactions of cyclic ethynylethylene carbonates have been intensively studied because of their robustness in new bond formation and diversified molecule construction. Known reaction modes usually involve a substitution step occurring at either the propargylic or terminal alkyne positions. Here, we report an unprecedented reaction pattern in which cyclic ethynylethylene carbonates first undergo a rearrangement to release allenal intermediates, which subsequently react with diverse nucleophiles to furnish synthetically useful allylic and propargylic allenols, phosphorus ylides, and cyclopropylidene ketones through an addition process rather than a substitution pathway. The products enable various further transformations, and mechanistic studies and theoretical calculations reveal that the reaction does not proceed via a semipinacol type [1,2]‐hydride shift, but through base‐mediated deprotonation as the key step to induce the rearrangement.