C CHEMISTRY; METALLURGY
C07 ORGANIC CHEMISTRY
C07D HETEROCYCLIC COMPOUNDS
515/00 Heterocyclic compounds containing in the condensed system at least one hetero ring having nitrogen, oxygen, and sulfur atoms as the only ring hetero atoms, not provided for in groups C07D463/00, C07D477/00 or C07D499/00 - C07D507/00
C07D515/02 in which the condensed system contains two hetero rings
C07D515/04 Ortho-condensed systems