The use of 9-and 2-aminophenanthrene for the preparation of tribenzo-and benzonaphtho-acridines and related heterocycles has been investigated : with 2-aminophenanthrene, the site of the acridine cyclisations is shown to be position 1. Benzoindenoacridines isosteric with benzonaphthoacridines were prepared from 4-aminofluorene.
The behaviour of 5H-benzo [b] carbazole and its N-acetyl derivative in various substitution reactions has been investigated, and results are discussed in relation to the current theoretical concepts concerning the electronic structure of the 5H-benzo[b]carbazole molecule.91 -Gif-sur-Yvette, France THE chemistry of 5H-benzo[b]ca.rbazole (I), an important constituent of coal-tar and possibly of tars from other sources, has scarcely been investigated. This heterocycle interests us because although it is itself devoid of carcinogenicity, some of its derivatives, particularly its amines, might prove a ~t i v e . ~We therefore investigated some substitution reactions of (I) and its N-acetyl derivative, including nitration, nitrosation, bromination by N-bromosuccinimide, and Friedel-Crafts acylation.
In the Conrad-Limpach reaction, 3-phenanthrylamine undergoes cyclisation a t position 4 in accordance with Marckwald's rule, but in the Ullmann-Fetvadjian condensation with @-naphthol and paraformaldehyde, and in the Bernthsen cyclisation of N-(@-naphthyl) -3-phenanthrylamine, the cyclisation at position 2 predominates.A4s in the Skraup reactionJ2 2-phenanthrylamine undergoes the Ullmann-Fetvadjian cyclisation with naphthols and paraformaldehyde at position 1 ; similar benzonaphthacridines have been obtained from N-aryl-2-phenanthrylamines in the Bernthsen r e a ~t i o n . ~ W' e have investigated the behaviour of 3-phenanthrylamine and its N-aryl derivatives in these two acridine syntheses. The Skraup reaction of 3-phenanthrylamine involves exclusively position 4; if this is also the case for the Ullmann-Fe tvadj ian and Bern thsen reactions, the products would be sterically overcrowded non-planar molecules such as (I) and ( 11).
R vWe found that 3-phenanthrylamine reacted with (3-naphthol and paraformaldehyde to give, in low yield, a mixture of two acridines. The main, high-melting cyclisation product was orange-yellow (its absorption spectrum showed bands up to 455 mp) and formed a blood red picrate ; these characteristics indicate the azanaphthacene structure (111) ; the isomeric minor product had a relatively low m.p., was almost colourless, and gave an orange-yellow picrate, features consistent with its formulation as benzo[a]naphth[2,1-jjacridine (11; R = H). This is a rare case where the formation of a nitrogen heterocycle does not follow Xarckwald's rule,4 because of the steric strain connected with an angular cyclisation. Similarly, N-(a-naphthyl)-3-phenanthrylamine underwent a modified Bernthsen reaction with acetic anhydride and zinc chloride to give small amounts of an orange-yellow, high-melting acridine, which formed a deep red picrate; these properties are consistent with its formulation as the linear compound (IV). In this reaction, probably because
The behavior of 4H‐benzo[d,e,f]earbazole and its N ‐aeetyl derivative in various electrophilic substitution reactions (e.g. nitration, nitrosation, bromination, Friedel‐Crafts acylations) has been investigated, and a number of new derivatives of this heterocycle (some of which are to be tested as potential carcinogens and enzyme‐inducers) have been synthesized.
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