Dithiolates nomenclature

Other structures such as a-(l,2-dithiol-3-ylidene)ketones (12) can be named according to common nomenclature because they do not possess the symmetry of the l,6,6a Slv-trithiapentalenes. However, even with such unsymmetrical systems, pentalene names may be useful, either to stress the fact that three heteroatoms are in line or to show the similarity with trithiapentalene derivatives, for instance, in the case of selenium analogs (13). 

The mesoionic l,3-dithiol-4-ones of type (2) are best represented as resonance hybrids of several limiting formulae (2a)-(2e), of which (2a) and (2b) are presumably most representative both formulae are, for example, in good agreement with the direction of the dipole moments. According to the IUPAC nomenclature rules, the mesoionic 1,3-dithiolones (2) should be named as l,3-dithiolylium-4-olates (B-79MI43202). 

The naming of these three heterocyclic fused (5 5 5) ring systems has been done according to the lUPAC system of nomenclature. Some examples are given below. Compound (1) (Table 1) is named 5/f-dipyrrolo[l,2-c 2, r-e]imidazole. Compound (10b) (Table 2) is 2,6-dibromodi-thieno[3,2-6 2, 3 -t/]thiophene. Compound (23) (Table 3) is 5A - l,2]dithiolo[l,5-(>]thieno[2,3-<(][ , 2]dithiole. The names of compounds (41b) and (43) (Table 5) are 2a-aza-l-phenyl[2.2.2]cyclazine and 5-phenyl-l-thia[2.2.2]cyclazine respectively. Compounds (45) and (46) (Table 6) have been given the names hexahydro-6b//-2a,4a,6a-triazacyclopenta[cd]pentalene and 2-alkyl-3,4-dicarbo-methoxy-l,6a-diaza[2,2,2]cyclazine respectively. Finally compound (50) (Table 7) is named 2,2a,4,4a,6,6a-hexahydro-l,3,5-trithia-7-azacyclopenta[cd]pentalene. 

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