Gold-Catalyzed Oxidative Reactions of Propargylic Carbonates Involving 1,2-Carbonate Migration: Stereoselective Synthesis of Functionalized Alkenes

A gold-catalyzed oxidative reaction of propargylic carbonates or acetates using 3,5-dichloropyridine as the oxidant has been developed. The reaction provides efficient access to α-functionalized-α,β-unsaturated ketones with excellent regio- and diastereocontrol via a regioselective attack of the N-oxide to the gold-activated alkyne followed by a 1,2-carbonate migration. In addition, the alkene products could be further transformed into the valuable 5-hydroxycyclopent-2-enones via cyclocondensation with acetone or cyclodimerization under basic conditions.