Before naming a polycyclic parent hydride containing a fused ring system it is necessary to identify the bridges (if any) which are treated separately from the ortho- or ortho- and peri-fused system (see FR-8).
FR-3.2 Selection of components
Each ring and/or combination of rings in a fused ring system is considered in order to select the parent component(s) (see FR-3.3). The first-order attached component(s) is then selected (if necessary) followed by second-order attached component(s) and higher-order attached components (see FR-3.4). It should be noted that when a heteroatom is common to two components it must be indicated in the name of each component.
Example:
If an atom is in a non-standard valence state this is indicated using the
Example:
Note
FR-3.3 Selection of parent component(s)
The ring or rings selected as the parent component are those most preferred by the criteria of FR-2.3 (see examples therein). The parent component may be identified in more than one location in a fused ring system by using different rings or combinations of rings. Such alternative locations of the parent component may be overlapping; or directly fused together; or separated by one or more components. When there are alternative locations for the parent component(s) the criteria of FR-3.3.1 are used to select the preferred location(s).
FR-3.3.1 Order of preference between locations for parent components
If there are two or more potential locations for a parent component the following criteria apply in order until a distinction is obtained. If a partial distinction is obtained the following criteria are only applied to distinguish between remaining choices. In the examples below the preferred location(s) is identified by a complete box and other locations with a dashed line. In the examples below second-order components are in bold type.
a. The location that enables the whole ring system to be named by fusion nomenclature is preferred to one where alternative approaches are required (see FR-7).
Example:
Note
b. The location that results in a name which does not require higher-order attached components. Second order component names are shown in bold below.
Examples:
c. The location that results in the maximum number of first-order attached components (then second-order etc.).
Examples:
d. A location that permits the expression of the maximum number of identical attached components with multiplicative prefixes.
Example:
e. A location that uses a preferred interparent component.
Example:
f. A location that results in preferred attached components (see FR-3.4) comparing first-order attached components, then their attachment locants (see FR-4.5), then comparing the preferred second-order attached components in order of the priority of the first-order components to which they are attached, then their attachment locants (see FR-4.5), then third-order components, etc.
Examples:
17. IUPAC, Treatment of variable valence in organic nomenclature (lambda convention), Pure Appl. Chem. 56, 769-778 (1984).
Return to home page for Fused Ring Nomenclature.
imidazo[2,1-b][1,3]thiazole ![[lambda]](../greek/LAMBDA.GIF)
-convention (ref 17). The bonding number n is cited as a superscript i.e. n, together with the locant of the atom with a non-standard valence state, in front of the name of the fused ring system (see FR-9.1).
55-phosphinino[2,1-d]phosphinolizine
Fusion nomenclature provides no means of describing the fusion of one component to two other components which are themselves fused together. If this problem arises see FR-7 for examples and how to name them.
cyclopenta[ij]pentaleno[2,1,6-cde]azulene
not 1,9-methenopentaleno[1,6-ef]azulene
nor 1,9-methenodicyclopenta[cd,f]azulene
With this criterion CAS and Beilstein permit the use of a less preferred parent component or attached component if that enables the whole system to be named by fusion nomenclature (See however FR- 7.1 and FR-7.1.1).
cyclopenta[h]indeno[2,1-f]naphtho[2,3-a]azulene
not benzo[a]benzo[5,6]indeno[2,1-f]cyclopenta[h]azulene
nor benzo[5,6]indeno[1,2-e]indeno[2,1-h]azulene
(no second-order components in preferred name)
difuro[3,2-d:3',2'-d']furo[3,2-b:4,5-b']difuran
not bis(furo[3',2':4,5]furo)[3,2-b:2',3'-d]furan
nor furo[2",3":4,5;5",4":4',5']difuro[2,3-b:2',3'-b']difuran
(no second-order components in preferred name) 
quinoxalino[2,3-b]pyrazino[2,3-g:5,6-b']diquinoxaline
not quinoxalino[2,3-b]quinoxalino[2',3':5,6]pyrazino[2,3-g]quinoxaline
nor quinoxalino[2",3'':5',6']pyrazino[2',3':6,7]quinoxalino[2,3-b]quinoxaline
(no second-order components in preferred name) 
dicyclopenta[h,h']phenanthro[2,1,10-def:7,8,9-d'e'f']diisoquinoline
not cyclopenta[h]cyclopenta[7,8]anthra[2,1,9-def:6,5,10-d'e'f']diisoquinoline
(no second-order components in preferred name)
dibenzo[c,g]phenanthrene
not naphtho[2,1-c]phenanthrene
(2 attached components preferred to 1)
benzo[de]benzo[1,10]phenanthro[4,3-g]isoquinoline
not naphtho[3',2',1':8,9]anthra[3,2,1-de]isoquinoline
nor dibenzo[5,6:8,9]phenanthro[2,3,4-de]isoquinoline
(2 first-order attached components preferred to 1)
difuro[3,2-b:2',3'-d]furan
not furo[3,2-b:4,5-b']difuran
(2 attached components preferred to 1)
(multiplicative name preferred to multiparent name) 
dinaphtho[1,2-c:2',1'-m]picene
not benzo[c]phenanthro[2,1-m]picene
1H-dipentaleno[2,1-e:2',1'-e']cyclopenta[1,2-a:4,3-a']dipentalene
not 1H-cyclopenta[e]pentaleno[2,1-e']pentaleno[2,1-a:5,4a']dipentalene 
anthra[2,1,9-def:6,5,10-d'e'f']diisoquinoline
not phenanthro[2,1,10-def:7,8,9-d'e'f']diisoquinoline
(anthracene preferred to phenanthrene) 
cyclopenta[5,6]phenanthro[3,2,1-de]indeno[4',5':5,6]indeno[2,1-g]isoquinoline
not cyclopenta[7,8]naphtho[2,1-g]indeno[5',4':6,7]fluoreno[3,2,1-de]isoquinoline
(phenanthrene preferred to fluorene)
10H-dibenzo[4,5:6,7]-as-indaceno[1,2-h]indeno[2',1':5,6]naphtho[2',3':7,8]fluoreno[1,2,3-de]isoquinoline
not 10H-benzo[7,8]indeno[2',1':5,6]fluoreno[1,2,3-de]benzo[6,7]naphtho[2',3':4,5]-as-indaceno[1,2-h]isoquinoline
[at first-order level both names have fluorene[1,2,3-de] and as-indacene[1,2-h] with the same attachment locants, however fluorene is preferred to as-indacene;
comparing the preferred second-order component attached to fluorene in each case naphthalene (preferred to indene) is preferred to indene (preferred to benzene)] 
fluoreno[9,1,2-cde]indeno[1,2-h]isoquinoline
not fluoreno[1,2,3-de]indeno[1,2,3-ij]isoquinoline
(cdeh preferred to deij)
Reference for this Section
Continue with FR-3.4 Selection of Attached Components.