Reactions involving shifting of the double bond in cyclic ethers

4-Methylenetetrahydropyran undergoes isomerization to 4-methyl-5,6-dihydropyran in the presence of sodium on aluminum oxide. Both pyrans are converted to a vinyl ether, viz., 4-methyl-2,3-dihydropyran, under the influence of iron pentacarbonyl.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 318–320, March, 1985.