Carbazoles, -annelated

The oxygen transfer to the -acetylenic carbon results in the very intense benzoyl cation, whereas the transfer to the a-carbon, via a series of fragments corresponding to the loss of OH , CO and CO2, respectively, leads to annelated heterocycles such as the radical cation of carbazole, as a result of elimination of CO81. The generation of the benzoyl cation was rationalized as shown in Scheme 1281. 

Electron impact induced fragmentation of 2-nitrodiarylamines has been studied. An important path is the annelation to carbazoles, as illustrated by the fragmentation of 2-phenylamino-3-nitropyridine103 see Scheme 33. The identity of the product ions was confirmed by collision activation MS upon comparison with authentic samples103. 

In 1984, Giibble et al. reported for the first time a novel l,10-bis-(6-methyl-5H-benzo[fc]carbazol-ll-yl)decane (469) which has potential bifunctional nucleic acid intercalating properties (406). To function as anti-tumor active drugs, one of the most important cytostatic mechanisms of action of coplanar annelated polycyclic compounds is their intercalation with DNA (405). Ten years later, Kucklander et al. studied a series of 5H-benzo[ 7]carbazole quinone derivatives for their cytotoxic activity against colon and lung cancer cells, and found that the heteroannelated 5H-benzo[ 7]carbazole quinone derivative 470 was the most active among the various analogs (407) (Scheme 4.2). 

The annelation of indoles to produce carbazoles is also frequently a satisfactory synthetic process. Reaction of 5-, 6- or 7-methoxyindole with 2,5-hexanedione, for example, gives... 

Vinylindoles are also efficient 47r-components in cycloaddition reactions and provide the corresponding [c]-annelated carbazoles which react, for example, with NPMI, MA, and quinones [82CJC419 83IJC(B)1004 88HCA1060] (Scheme 6). Although in the more usual cases the result of... 

Nitrosonium terafluoroborate initiates the cation radical-mediated imino-Diels-Alder reaction of IV-arylimines with IV-vinylpyrrolidinones to give cw-4-(2-oxopyr- (g) rolidin-l-yl)tetrahydroquinolines.175 Also, 2,4,6-triphenylpyrylium tetrafluoroborate catalyses the Diels-Alder addition of IV-arylimines with IV-vinylpyrrolidinone and IV-vinylcarbazole to yield the corresponding 2-oxopyrrolidin-l-yl- and carbazole-9-yl-tetrahydroquinolines.176 The tricyclic core (151) of the batzelladine alkaloids has been prepared by a diastereoselective 4 + 2-annelation of the vinylcarbodiimide (150)... 

Pyrroles, H.M.L. Davies. Synthesis of Porphyrins with Exocy-clic Rings from Cycloalkenopyrroles, T.D. Lash. Palladium-Catalyzed Coupling Reactions of Indoles, A.R. Martin and Q. Zheng. Cycloaddition Reactions of Indole Derivatives, U. Pindur. Transition-Metal Mediated Synthesis of Carbazole Derivatives, H. J. Knoiker. Synthesis of [b]-Annelated Indoles by Thermal Electrocyclic Reactions, S. Hibino and E. Sugi-no. Total Synthesis of (-) and ent (-) Duocarmycin SA, D.L. Boger. Index. I... 

The effect of annelation is again seen in a comparison of [Eqs. (67) and (68)]. 183 (R = 0) gives 184 as the main product whereas 187 gives 188 and very little, if any, ring contraction product 56) d) xhe same increase in the rate of ring contraction as opposed to intramolecular cyclization to carbazole derivatives was also observed in 3-phenyl-2-quinoxalylnitrene [(740, Eq. (46)]. 

Three separate methods were developed for the synthesis of 2,3 -bisindolylmethanes 177 <0451187>. These compounds were converted into indolo 3,2-i)lcarbazoles by an acid-catalyzed annelation reaction with triethyl orthoformate. A new synthesis of the structurally related indolo 3,2-a carbazoles involved the cyclocondensation of 2,3 -biindoles with dimethylaminoacetaldehyde diethyl acetal <04TL7273>. 

Electrophilic annelation has also been used to convert indoles to carbazoles. The condensation of amines with 2,5-dimethoxytetrahydrofuran, which is a very useful method of synthesis of pyrroles (see Section 2.03.2.7), if carried out for an extended period, gives JV-substituted carbazoles. This reaction occurs by two successive annelations (Scheme 139) <86T2l3l>. 

Orf/io-quinodimethanes have been used in numerous S3mthetic applications for the construction of various polycyclic ring systems found in structurally complex target molecules, via [4+2] Diels-Alder type cycloadditions. In this context, indolo-2,3-quinodimethanes have become increasingly useful as synthetic precursors to a variety of interesting [6]annelated indoles, carbazoles, and alkaloids [111]. 

The intramolecular Diels-Alder reaction of 2-pyrones with alkynes has recently been exploited in synthesizing [a]-annelated carbazoles 11, [c]-annelated carbazoles 12, and lycorine alkaloids 13. ... 

Scheme 6.20 A novel access to annelated carbazoles, an important class of compounds used in optoelectronics, semiconducting materials, and organic light emitting diodes...

Synthesis of [6]-annelated indoles by thermal electrocyclic reactions 95MI7. Transition metal-mediated syntheses of carbazole derivatives 95MI6. Vilsmeier-Haack and Friedel-Crafits reactions, bromination, debromination, debenzylation in indole series and their synthetic application 99YZ35. 

The combination of benzimidazolone moieties with the triphenedioxazine chro-mophore leads to imidazolone-annellated triphenedioxazine pigments, also called benzimidazolone-dioxazine pigments (4). In these pigments, the carbazole fragments of P.V. 23 are replaced by benzimidazolone moieties (Figure 20.6). 

A series of ethyl 2-R(Ar)-9-cyclopropyl-4-fluoro-6-oxo-lH-imidazo[4,5-/i] quinoline-7-carboxylates 78 have been obtained through cyclocondensations of the corresponding 7,8-diamino qninolones [233], Also a number of tetracyclic [h]-annelated fluoroquinolones, snch as l-cyclopropyl-6-fluoro-4-oxo-l,4-dihydro-pyrido[2,3-fl]carbazole-3-carboxylic acids 79 and their thiene isosters have been obtained (Scheme 36) [198], All derivatives proved to possess a high activity against Bacillus subtilus and Staphylococci. 

Pindur U., Kim M.H., Rogge M., and etc. New Diels-Alder reactions of (E/Z)-2 -methoxy-substituted 3-vinylindoles with carbo- and heterodieno-philes region- and stereoselective access to [b]-annelated indoles and functionalized or [a]-annelated carbazoles . -J. Org. Chem., 1992, v. 57, Jib 3, p. 910-915. 

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