the oxygen-containing ring being six-membered

Full Title

Heterocyclic compounds containing in the condensed ring system both one or more rings having oxygen atoms as the only ring hetero atoms and one or more rings having nitrogen atoms as the only ring hetero atoms, not provided for by groups C07D451/00 - C07D459/00, C07D463/00, C07D477/00 or C07D489/00 > in which the condensed system contains two hetero rings > Ortho-condensed systems > with only one oxygen atom as ring hetero atom in the oxygen-containing ring > the oxygen-containing ring being six-membered