Polycyclic systems including two heterocycles

One Nitrogen Atom (it is self-sub divided into Monocyclic Pyrroles, Hydropyrroles, Porphyrins and Related Systems, Indoles, Carbazoles, Related Systems, and Hydrogenated Derivatives, Isoindoles Including Phthalocyanins and Porphyrazines, Polycyclic Systems Including Two Heterocycles). 

A large number of polycyclic heterocycles containing two or more six-membered rings that share two or more carbon atoms are known. For the majority of these systems, only one of the six-membered rings contains the heteroatoms and the other rings are fused carbocyclic rings such as cyclohexane, benzene, naphthalene, and in rare examples, anthracene. Systems in which more than one of the six-membered rings contain heteroatoms are also briefly discussed these include spiro-cyclic compounds and substituted naphthalenes. 

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