with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring atoms

Full Title

Heterocyclic compounds containing four-membered rings having one oxygen atom as the only ring hetero atoms > not condensed with other rings > having no double bonds between ring members or between ring members and non-ring members > with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring atoms