Indoles nomenclature

Pyrido[ 1, 2 1,2]imidazo[4,5-b]quinoxaline nomenclature, 1, 22 2,2 -Pyridoin synthesis, 2, 337 Pyrido[ 1,2-6]indazoles synthesis, 5, 335 E ridoindoles rearrangement, 4, 508 Pyrido[a]indoles synthesis, 4, 233 Pyrido[6]indoles nomenclature, 4, 498 Pyridooxadiazolones ring contraction, 4, 149... 

Many names in common use for heteropolycycles provide little or no information about structure. Most such names were introduced long before any serious attempts were made to systematize nomenclature, and although more systematic equivalents can now be coined in many cases (for example, indole can be named benz[f)]azole or 1-azacyclopentabenzene), it is likely that the use of a substantial residue of trivial names will continue. However, one would not expect many new trivial names to be introduced in the future, except in the natural product area (see Section 1.02.4). 

An alternative form of spiro nomenclature more common in Europe than in America is similar to that used in examples (64)-(66), but the order of citation of components is based on size, and the term spiro appears between the component names (see lUPAC Blue Book B-79MI10200) Rule B-11). Thus (64) would be called 3H-indole-S-spiro-l -cyclopenta-2, 4 -diene, and (63) would be cyclohexanespiro-4 -[l,3]dithian-2 -spirocyclopentane. 

According to the Ring Index, the system is classified as pyrido-indole and numbered as in 6 (harmine = 7-methoxy-1-methyl-9 -pyrido[3,4-fc]indole). This is the nomenclature adopted by Chemical Abstracts, according to which a-carboline (5) is 9 -pyrido[2,3-6]indole, jS-carboline (6) is 9jy-pyrido[3,4-6]indole, y-carboline (7) is pyrido[4,3-6]indole, and S-carbohne (8) is 5jy-pyrido[3,2-fc]indole. 

In indole, benzimidazole, and their derivatives, all symmetry restrictions on the IPA and 2PA allowedness of transitions are lifted. In these molecules. La and Lb transitions are not formally defined. However, bands in the low-energy portion of the IPA and 2PA spectra can be assigned to transitions which have similar characteristics to the La and Lb transitions of benzene (although they are red-shifted with respect to benzene or toluene), so the nomenclature is often extended to these systems. 

Before this is closed, a couple of points need be made regarding nomenclature. Older literature uses alpha for the 2-position of the indole ring. Thus, alpha-methyltryptamine, in early literature, refers to the indole-2-methyl, not to a side-chain methyl derivative. Throughout TiHKAL, the numbers are devoted to the indole ring, and the alpha and beta terms to the side-chain. And the use of the letter N refers to the side-chain amino nitrogen atom. The pyrrole nitrogen is the indole position 1. 

As would be expected, the majority of the compounds described in this chapter can be considered as indoles with one or more nitrogens as heteroatoms in the six-membered ring. The four pyrrolopyridines are commonly referred to as azaindoles, terms more elegant than the IUPAC nomenclature. These compounds are also occasionally called diazaindenes. The following synonyms are frequently met ... 

Most authors restrict the azaindole nomenclature to these four compounds, which have been reviewed under this name (68AHC(9)27,68RCR5S1,80RCR428). The four pyrido[6]indoles are usually named (with IUPAC approval) as carbolines. For example, (5) is pyrido[3,4-6]indole or /3-carboline isomers with the pyridine nitrogen in the positions indicated are a-, y- and 5-carbolines respectively. The carbolines have been reviewed (B-61M130900, 64AHC(3)79>. 

Nitrogen heterocyclic systems, Claisen rearrangements in, 8, 143 Nomenclature of heterocycles, 20, 175 Nuclear magnetic resonance spectroscopy, application to indoles, 15, 277 Nucleophiles, reactivity of azine derivatives with, 4, 145... 

The nomenclature of peri-naphthalene heterocycles does not follow a common principle. In many original papers, the names of heterocyclic systems are derived from the corresponding peri-annelated hydrocarbon derivatives (1,2-diazaacenaphthylene, 1-oxaphenalene, etc.), from monoheterocycles with an indication of linked positions (naphtho[l,8-6c]furan, naphtho[l,8-de]azepine, etc.), and from benzoannelated heterocycles (benzo[o/]indole, benzo[heterocyclic systems and some compounds have trivial names, for instance, perimidine, naph-thostyryl, and naphtholactone. Moreover, it is necessary to remember some peculiarities in the electronic structure of peri-annelated heterocycles, namely the absence of independent existance of the 7r-closed-loop monoheterocycles which could be a fragment of peri-annelated heterocyclic systems. Therefore, the separation of a heterocycle from the united 7r-system is impossible. In this case, the simplest structure and the tt-electron unit is the whole peri-heterocyclic nucleus. 

It could be more correct to form peri-heterocyclic nomenclature in accordance with the unified principle based on the names of the corresponding peri-cyclic hydrocarbons for example, 1-azaacenaphthylene instead of benzo[cc/]indole and 1-oxaphenalene instead of naphtho[bc]py-rane. However, we tried to use as a rule the adopted names. Moreover, for... 

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