1.2 Cyclic Systems
61
8
H2
1
~
N2
6 N ~ 2
~ 5 Y
.... N
II
c 1
~ c'
I
5N
- -
/:.
8H-Indeno [1,2-c: 5,6-c'] dipyrazole
4
Conclusive peripheral numbering of fused heterocyclic systems must first
of all pay attention to the generalized orientation rules detailed for corresponding carbocyclics (p. 22). If these are not sufficient, that orientation is
chosen which leads to lowest locants by evaluating the following criteria
one after another:
a) for hetero atoms as a whole (but see p. 55),
b) for hetero atoms according to the "a" term seniorities (Tables 4,20),
c) for C atoms common to two or more rings,
d) for hetero atoms of the same element that are not in fusion positions,
e) so that an internal hetero atom lies as close as possible to the lowest
numbered fusion position,
f) for indicated hydrogen.
It should be noted once again that hetero atoms in fusion positions are
numbered sequentially by plain numbers and taken into account in the
names of both components to be fused together.
The following more complex examples may illustrate and clarify these
fusion and numbering principles.
15
rj1~d
~N
09
1 2 \ d
[1,2]Diazeto[ 1,2-d]phenanthro[9, 10-b] [1,4,5]oxadiazepine
13H-Dibenzo[ 4,5: 6,7]indeno[2,I-c ] pyridine