SEARCH Articles Figures Tables Five-membered Nitrogen- and Oxygen-containing Rings Five-membered Oxygen-containing Rings Four-membered Rings containing Oxygen and One Sulphur Atom Four-membered Rings containing Sulphur and Oxygen Heterocycles containing both oxygen and sulfur in the same ring Hydrogenation of Oxygen- and Sulfur-containing Aromatic Ring Systems Medium-sized-ring Oxygen-containing Heterocycles Nitrogen- and Oxygen-containing Rings Oxygen containing Oxygen ring Oxygen-containing Compounds with More than One Ring Oxygen-containing furan-ring derivatives Oxygen-containing medium-sized-ring Ring Systems Containing One Oxygen or Sulfur Ring oxygenation Six-Membered Rings containing Oxygen or Sulphur Six-membered Nitrogen- and Oxygen-containing Rings Six-membered oxygen-containing rings Six-membered oxygen-containing rings saturated, analysis Six-membered ring heterocycles containing one oxygen atom Sulfur-Nitrogen Rings Containing Exocyclic Oxygen