Enantioselective Medium-Ring Lactone Synthesis through an NHC-Catalyzed Intramolecular Desymmetrization of Prochiral 1,3-Diols

A highly enantioselective
intramolecular annulation reaction of
1,3-diols catalyzed by a triazolium N-heterocyclic carbene (NHC) precatalyst
is disclosed, affording the corresponding medium-sized lactones in
moderate to good yields with high enantioselectivities. It is worth
noting that this compatible catalytic system has been successfully
applied to assemble a broad range of chiral medium-sized lactones,
including ones with eight-, nine-, ten-, eleven-, and twelve-membered
rings.