58
1 Parent Structures
b) The next criterion gives preference to a component containing nitrogen
(because of the overwhelming significance and sheer abundance of
nitrogen cycles).
1
6Nao20 12
I
c 3
~
Pyrano [2,3-c ]pyrrole
[1,3] Oxaphosphinino [4,5-b] azirine
Formerly: [1,3] Oxaphosphorino [4,5-b] azirine
c) If no nitrogen-containing ring is present, priority is given to that component which includes at least one senior element according to the table
of "a" terms (nothwithstanding ring size and number of other hetero
atoms).
[1,2]Phosphaborinino[5,4-b ]furan
7,8-Dihydro-6H- [1,4]dithiino[2,3-b ]pyran
d) If still no decision is possible, precedence is given to the (trivial) component having the largest number of rings.
7
7H-Pyrazino [2,3-c] carbazole, not:
7H-Indolo [3,2-f] quinoxaline