FR-7 Three Components ortho- and peri-Fused Together

Contents of Section

FR-7. Three Components ortho- and peri-Fused Together
FR-7.1 Use of replacement nomenclature
FR-7.1.1 Use of less preferred hydrocarbon parent component
FR-7.2 Use of bridging nomenclature

Continue with FR-8 Bridged Fused Ring Systems

The fusion principles described above only apply between pairs of components. It is not possible to name a system where a third component is ortho- and peri-fused to two components which are themselves ortho- or ortho- and peri-fused together. To avoid this situation the following procedures are applied in order until a name can be formed. However if one of the three components is a benzene ring and another is a heteromonocycle then application of FR-2.2.8 will sometimes permit normal fusion procedures that would not otherwise be possible.

Example:

2H-[1,3]benzodioxino[6',5',4':10,5,6]anthra[2,3-b]azepine

FR-7.1 Use of replacement nomenclature

If the corresponding hydrocarbon fused ring system can be named by fusion principles or has a trivial name then the heteroatoms are identified by replacement nomenclature using 'a'-terms.

Examples:

1,2,3,4,5,6-hexaazacyclopenta[cd]pentalene

1,3a¹,4,9-tetraazaphenalene
(See FR-5.5.2)
CAS and Beilstein name 1,4,9,9b-tetraazaphenalene

3-oxa-6-azacyclopenta[b]cyclopropa[de]naphthalene
CAS name cyclopropa[4,5][1]benzopyrano[6,7-c]pyrrole
Beilstein name cyclopropa[4,5]chromeno[6,7-c]pyrrole

2H-10-oxanaphtho[2,1,8-cde]azulene
CAS name 1H-benzo[ef]cyclopenta[jk][2]benzoxepine

Note

CAS and Beilstein use less preferred components in preference to replacement if by this device fusion nomenclature can be used. See last two examples above.

FR-7.1.1 Use of less preferred parent component

If the corresponding hydrocarbon fused ring system cannot be named by the fusion principles outlined above then a less preferred parent component is selected which will permit fusion nomenclature to be used.

Examples:

cyclobuta[1,7]indeno[5,6-b]naphthalene
not cyclobuta[cd]naphtho[2,3-f]indene
(naphthalene preferred to indene)

10-azacyclobuta[1,7]indeno[5,6-b]anthracene

FR-7.2 Use of bridging nomenclature

If the fused ring system cannot be named on the basis of normal fusion nomenclature, or the use of replacement nomenclature with the corresponding hydrocarbon, or even when using a less preferred parent component, then it is treated as a bridged fused system (see FR-8). The fused ring portion should be selected using FR-8.2.

Examples:

1,12-ethenobenzo[4,5]cyclohepta[1,2,3-de]naphthalene
not 1,12-ethenobenzo[c]phenanthrene
(preferred fused ring system, see FR-8.2.d; 7,6,6,6 rings preferred to 6,6,6,6 rings)

8,7-(azenoetheno)cyclohepta[4,5]cycloocta[1,2-b]pyridine
not 6,7-buta[1,3]dienocycloocta[1,2-b:5,6-c']dipyridine
(maximum number of atoms in fused ring system, see FR-8.2.b)
CAS name 8,7-(nitriloetheno)cyclohepta[4,5]cycloocta[1,2-b]pyridine
Beilstein name 8,7-epi[1]azaprop-2-en-3-yl-1-ylidene-cyclohepta[4,5]cycloocta[1,2-b]pyriine

Return to home page for Fused Ring Nomenclature.