Preparation of cyclic ethers for polyether synthesis by catalytic ring-closing enyne metathesis of alkynyl ethers

Alkenyl-substituted six- and seven-membered cyclic enol ethers, which are potential building blocks for the synthesis of marine polyether natural products, can be prepared in high yield (70–97%) from alkynyl ethers by ruthenium-catalysed ring-closing enyne metathesis. The carbene-bearing ruthenium complex is generally the most efficient catalyst for the reaction.