Iodocycloisomerization/Nucleophile Addition Cascade Transformations of 1,2-Alkynediones

A general electrophilic iodocyclization/nucleophile
addition cascade
transformation for 1,2-alkynediones for the synthesis of various oxygen
heterocycles and access to regioselective alkyne hydroxylation is
reported. Furan-tethered ynediones resulted in the construction of exo-enol ethers via carbonyl-alkyne cyclization-initiated
heteroarene dearomatization, whereas other (hetero)­arene-, alkenyl-,
and alkyl-tethered ynediones resulted in the formation of highly functionalized
3­(2H)-furanones. Importantly, the developed domino
protocols involve the construction of important heterocyclic scaffolds
and installation of two functional groups in a single operation. Moreover,
the use of water as a nucleophile resulted in regioselective alkyne
hydroxylation via furanone ring opening. The developed protocols are
characterized by a wide substrate scope, and their utility has been
demonstrated by a number of postsynthetic transformations.