A New Route to Crown Ethers by Ruthenium-Catalyzed Ring Closing Metathesis

Abstract
The ruthenium-catalyzed ring closing metathesis reaction of bis-allyl ethers of podands 1a-c and 8 gives macrocyclic crown ethers in good yield at room temperature. Only 1 mol% of the ruthenium-carbene complex 2 are necessary to catalyze the reaction. Cyclic products are obtained exclusively, even at high concentrations.