Dehydration of 1,4-, 1,5-, or 1,6-alkanediols overalumina at 220–250 °C in a distillation apparatus gave the corresponding 5- to 7-membered oxacyclanes in good yield of 51–71%. Diethylene glycol also gave 1,4-dioxane in 49% yield, whereas attempted one-step synthesis of crown ethers from polyethylene glycols in a similar manner resulted in the predominant formation of 1,4-dioxane without any trace