Trivial names fused heterocycles

Many heterocycles are fused to other ring systems, notably benzene, giving in this case benza derivatives some of these compounds are also extremely well known and have trivial names of their own, such as indole and. Here, however, it is possible to relate these compounds... 

The IUPAC nomenclature of S-atom PACs is also similar to that for N-PACs. Thus the trivial name thiophene (XIV) is a basis for the common names of S-heterocycles containing one endocyclic S-atom in a 5-membered fused ring. Addition of two benzo groups gives dibenzothiophene (XV) ... 

The benzo[a] (19), benzo[/t (15) and benzo[c] (16) fused heterocycles are heterocyclic analogues of naphthalene, with the dibenzo heterocycles (17) bearing a similar electronic relationship to phenanthrene. Some of these compounds are still known by their trivial names indole (15 Z = NH), isoindole (16 Z = NH), carbazole (18) and indolizine (19). The names thianaphthene and pyrrocoline for (15 Z = S) and (19) respectively are now little used. Particular confusion can arise in consulting... 

IUPAC/Chemical Abstracts System (IUPAC Rule B-3). The fusion operations described in Section II, A, 3, a are applied to trivial and/or Hantzsch-Widman names of heterocyclic (and, if present, car-bocyclic) components see examples 25-27. In addition a unit consisting of a benzene ring fused to a one-ring heterocycle can be considered as a single component. If this one-ring heterocycle contains 3-10 members it... 

Pyrimidine (1) is the trivial name for 1,3-diazine two me/a-oriented CH units in benzene have been replaced by nitrogen atoms. Quinazoline (2) is benzo-fused pyrimidine and is defined by the fusion nomenclature as benzo[if]pyrimidine, alternatively as 1,3-diazanaphthalene by the replacement nomenclature. Perimidine (3) is the trivial name for the pen -naphtho-fused pyrimidine system. It may be called (fusion names) l//-benzo[f/e]quinazoline or l//-naphtho[l,8-r/e]pyrimidine, or alternatively l//-l,3-diazaphenalene by the replacement nomenclature. However, the three trivial names are all system names accepted by lUPAC and approved as parents for further fusion name formation the benzo- and naphtho-pyrimidine names are therefore not used. In principle, additional rings can be fused onto the benzo or naphtho moiety in either quinazoline or perimidine without any profound alteration in heterocyclic reactivity. Aceperimidylene (4) and aceperimidine (5) are the trivial names for two cyclopenteno and cyclopentano fused perimidines. 

Systems in which at least two neighbouring atoms are common to two or more rings are known as fused systems. For several bicyclic benzo-fused heterocycles, trivial names are permitted, e.g. ... 

Quinoline and isoquinoline are heterocycles in which a benzene ring and a pyridine ring are fused through carbon. The isomeric heterocycles 1- and 2-azanaphthalene, better known by their trivial names quinoline and isoquinoline, have been the subject of extensive studies since their discovery in the extracts of coal tar at the beginning of nineteenth century. Since then their heterocyclic ring systems were found incorporated in several hundreds of natural products and were used as pharmacophore units in dozens of pharmaceuticals especially anti-bacterials, better known under the general name of Quinolones . ... 

Provided that no retained trivial name is applicable, fused heterocyclic systems are given Hantzsch-Widman names. Fusion of components follows the same pattern as established for corresponding hydrocarbons and an intricate series of seniority rules must be run through for selecting the parent component. Traditional abbreviated terms are retained for the following fusion components furo, imidazo, (iso)quino, pyrimido, thieno. 

Extended series of trivial names that are to be retained (or just too frequently used to be simply omitted) have already been compiled in various tables of Chapter 1 of this book (fused polycycles Table l,p. 16, heterocycles Tables 2 and 3, p. 44,50). For the numerous trivial names to be dealt with in the domain of the functional compound classes of Chapter 2 it has been found more appropriate not to include them directly in the text but to confine them to a tabular appendix. Specific hydrocarbon systems such as terpenes and steroids, whose nomenclature is widely dominated by trivial names, are also accounted for in this appendix. 

Stelzner Method. This is a general method of applying replacement nomenclature to ring systems it differs from the Chemical Abstracts procedure in that replacement principles are applied in all cases to the name of the hydrocarbon with the same bond distribution in the rings as the heterocycle to be named. This leads to no difference for monocycles (see examples 1-3), but in the case of fused skeletons the parent hydrocarbon of a fully unsaturated heterocycle is frequently a partially hydrogenated molecule. The parent hydrocarbon name for application of either replacement method can be trivial or a name derived by fusion principles (as above). The examples 21-24 of both... 

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