An Efficient Synthesis of Five-membered Cyclic Ethers from 1,3-Diols Using Molecular Iodine as a Catalyst

Intramolecular cyclic etherification of 1,3-diols was investigated using iodine as a catalyst under solution reaction conditions. Compounds containing five-membered ether rings were obtained. Propella ether (11-oxatricyclo[4.4.3.01,6]tridecane) was conveniently synthesized from 1,3-diol (6-(2-hydroxyethyl)spiro[4.5]decan-6-ol) in 97% yield via carbon skeleton rearrangement. Spiroethers and bicyclic ethers were also obtained from the corresponding 1,3-diols in yields of over 77%. The most suitable reaction conditions were a temperature of 80°C, a 1:0.2 molar ratio of 1,3-diol:iodine, and a time period of 8 h. In addition, terpenoic ethers were efficiently synthesized from the corresponding 1,3-diols, derived from (+)-camphor and (-)-fenchone, via skeleton rearrangement. In particular, the reaction of the 1,3-diol derived from (+)-camphor proceeded smoothly at room temperature with a yield of 91%. The yield of the cyclic ether using iodine as a catalyst was comparable to the method using sulfuric acid.