<i>syn-trans</i> Fused Bicyclic Ether Formation <i>via</i> Acetylene-biscobalthexacarbonyl Complex

Abstract

Abstract Medium size bicyclic ethers of 7-, 8-, and 9-membered rings were synthesized by connection between a hydroxy group on dihydropyranyl ring and a propargylic cation that was stabilized as an acetylene biscobalthexacarbonyl complex under acidic conditions. This cyclization selectively afforded the syn-trans bicyclic ring system often seen in marine toxins such as ciguatoxin.