Insertion of Isolated Alkynes into Carbon-Carbon σ-Bonds of Unstrained Cyclic β-Ketoesters via Transition-Metal-Free Tandem Reactions: Synthesis of Medium-Sized Ring Compounds.

The transition-metal-free insertion of isolated alkynes into carbon-carbon σ-bonds of unstrained cyclic β-dicarbonyl compounds has been reported. These tandem reactions offer an efficient synthesis of medium-sized ring or fused-ring compounds through ring expansion. The methodology has the potential to be widely used throughout organic synthesis due to the easily accessible starting materials and mild reaction conditions.