Synthesis of Fused Oxabicyclic Systems by Metal-Catalyzed Intramolecular Addition of 1,3-Cycloalkyldiones to Alkynes.

[reaction: see text] Readily available 4-propargyl-1,3-cyclohexanediones and cyclopentanediones can be chemo- and regioselectively cycloisomerized to synthetically appealing fused oxabicyclic systems by simply stirring at room temperature with catalytic amounts of an appropriate metal complex.