96206 ⎘
Compounds containing elements of Groups 5 or 15 of the Periodic System; Phosphorus compounds; Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having oxygen atoms, with or without sulfur, selenium, or tellurium atoms, as the only ring hetero atoms the oxygen atom being part of a three-membered ring condensed with carbocyclic rings or carbocyclic ring systems