90
2 Substituted Systems
It is tempting to envisage use of the cyclo procedure also for very simple
parent systems, above all when special relationships could thus be
expressed by the name itself, e. g.:
H
H
)cb(
H
H
1,4-Cyclobenzene
(Bicyclo [2.2.0 ]hexa -1,3,5-triene)
H
HAH N
3,5-Cyclopyridine
(Cyclopropa[ c]pyrrole)
Another very specific subtractive naming mode has been developed for
cyclic compounds containing (if only formal) contiguous double bonds -
cyclic cumulenes - whose treatment with conventional nomenclatural
means would often lead to rather cumbersome combinations of "ene",
"dehydro", and "indicated H" notations.
Substantial relief is provided here by the so-called delta convention
whose essence consists in identifying any skeletal atom at which two (or
more) double bonds (e.g.: m = 2,3) converge with a 6 m -symbol placed
immediately behind the corresponding locant and An-symbol, if present.
(Pure Appl. Chern. 1988, 60, l395).
56 2 - Dibenzo [a,d] cycloheptene
instead of:
4a,5-Didehydro-4aH-dibenzo [a,d] cycloheptene
8,8a -Dihydro-66 2 - [1,3] diphosphinino]1 ,2-d] [1,2,4] oxazaphosphole
instead of:
5,6-Didehydro-8,8a -dihydro-5H -[1,3] diphosphinino ...