Carbazoles oxidation

Carbazole oxidized by nickel peroxide in the absence of light and in the presence of 2-methyl-2-nitrosopropane gave the radical 71, an observation taken as additional evidence for the intermediacy of radical cations, trapped in this case by the nitrosoalkane, in oxidative dimerization of carbazoles (see Section II,A,2). 

Chromium-carbene complexes can be prepared from 2- and 3-substituted indolyllithium compounds and chromium hexacarbonyl, followed by methylation. These reactive species combine with alkynes to give cyclization products, which are oxygenated carbazoles. Oxidation to the quinone can be effected with ceric ammonium nitrate (can) where possible, otherwise the product is a cyclohexadiene (Scheme 66) <89JOC3249>. 

Dihydro-llH-benzo[a]carbazole oxidized with periodate according to Synth. Meth. 21, 182 ll,12-dihydro-5H-dibenz[b,g]azonine-6,13-dione (Y 85%) dissolved in 2 N NaOH, allowed to stand at room temp, overnight, and the resulting crude 4-quinolone refluxed 5 hrs. with PCI5 in POCI3 10-chloro-llH-indeno-[l,2-b]quinoline (Y 77%) hydrogenated 2 hrs. with 10%-Pd-on-carbon in methanol llH-indeno[l,2-b]quinoline (Y 91%). F. e. s. J. A. Beisler, J. Med. Chem. 14, 1116 (1971). 

Examples include luminescence from anthracene crystals subjected to alternating electric current (159), luminescence from electron recombination with the carbazole free radical produced by photolysis of potassium carba2ole in a fro2en glass matrix (160), reactions of free radicals with solvated electrons (155), and reduction of mtheiiium(III)tris(bipyridyl) with the hydrated electron (161). Other examples include the oxidation of aromatic radical anions with such oxidants as chlorine or ben2oyl peroxide (162,163), and the reduction of 9,10-dichloro-9,10-diphenyl-9,10-dihydroanthracene with the 9,10-diphenylanthracene radical anion (162,164). Many other examples of electron-transfer chemiluminescence have been reported (156,165). 

In Europe, where an abundant supply of anthracene has usually been available, the preferred method for the manufacture of anthraquinone has been, and stiU is, the catalytic oxidation of anthracene. The main problem has been that of obtaining anthracene, C H q, practically free of such contaminants as carbazole and phenanthrene. Many processes have been developed for the purification of anthracene. Generally these foUow the scheme of taking the cmde anthracene oil, redistilling, and recrystaUizing it from a variety of solvents, such as pyridine (22). The purest anthracene may be obtained by azeotropic distillation with ethylene glycol (23). 

No oxidizing agent is required for the sulfuric acid promoted cyclization of iV,iV-diphenyl-hydroxylamine to carbazole (13CB3304). The parallel conversion of diphenyl sulfoxide and diphenyl selenoxide to dibenzothiophene (23CB2275) and dibenzoselenophene (39CR(199)53l) is effected by treatment with sodamide. 

Considerable progress has also been made with the alternative line of work, the search for a synthetic analgesic as effective as morphine and without its disadvantages. The work of the American Committee has shown that it is possible to produce analgesics with a dibenzofuran or carbazole nucleus in place of the phenanthrene or phcnanthrylene oxide nucleus of morphine and it is stated that synthetic products with analgesic potency equal to that of codeine have been prepared. In the 1938 report moderate analgesic potency was recorded for preparation No. 421, 9-methyl-2-(l-hydroxy-3-diethylamino)-propylcarbazole at 10 mgm. by injection. 

While this work was in progress Spath and Bretschneider showed that strychnine, on oxidation with permanganate in alkaline solution, furnished W-oxalylanthranilic acid (VII), brucine yielding oxalyl-4 5-dimethoxy-anthranilic acid, the latter observation providing confirmation of the evidence previously adduced that the two methoxy-groups in brucine are in the oj Ao-position relative to each other as indicated by Lions, Perkin and Robinson. The results so far considered indicate the presence in brucine and strychnine of the complex (VIII), which can be extended to (IX) if account is taken of the readiness with which carbazole can be obtained from strychnine and brucine and certain of their derivatives by decomposition with alkali at temperatures ranging from 200° to 400°, Knowledge of the structure of the rest of the molecule is mainly due to the results of the exhaustive study by Leuchs and his pupils of the oxidation... 

The parent indolo[2,3-fl]carbazole (1) has also been the subject of a study probing its reactivity toward oxidizing agents. One of the substrates involved, namely 85 (prepared from 1 and 2,5-dimethoxytetrahydrofuran in the presence of acid), was subjected to treatment with m-chloroperbenzoic acid, to give the dione 86 as the major product and a sensitive compound assigned the hydroxy structure 87. A cleaner reaction took place when 85 underwent oxidation with tert-butyl hydroperoxide assisted by VO(acac)2, to produce 86 exclusively in 86% yield. Likewise, A,N -dimethylindolo[2,3-fl]carbazole furnished the dione 88 on treatment with this combination of reagents (96J(X 413). 

The yellow colored, sparcely soluble 5-ethyl-2-methyl-l l/f-pyrido[3,4-u] carbazolium 347 isolated from Aspidosperma gilbertii exists as a hydroxide after filtration of the corresponding iodide over basic aluminum oxide. A short synthesis was described (80CB3245). The Pyrido[3,4-a]carbazole ring system is present in the alkaloid AG-1, whereas Cryptolepine (348) possesses the indolo[3,2-b]quinoline moiety (65MI1). 

A solution of 3.5 g 4-(2,3-epoxypropoxy)carbazole in 50 ml absolute alcohol is mixed with 30 ml isopropylamine and heated for 3 hours under reflux. When the reaction is finished, the reaction mixture is evaporated to dryness. The residue obtained is taken up in methylene chloride and chromatographed over an aluminum oxide column (300 g basic aluminum oxide, activity stage IV eluent methylene chloride). The eluted fractions are evaporated and the residue is dissolved in methanol and acidified with 2N ethereal hydrochloric acid. 

Because reduction of 2-nitrodiphenyl with hexamethyldisilane 857 does not give any carbazole, nitrene intermediates can probably be excluded. The very polar 4-nitropyridine N-oxide 1003 can be reduced by 857 only in the polar solvent N,N-di-... 

Resnick SM, DS Torok, DT Gibson (1993) Oxidation of carbazole to 3-hydroxycarbazole by naphthalene 1,2-dioxygenase and biphenyl 2,3-dioxygenase. FEMS Microbiol Lett 113 297-302. 

Pyrrole derivatives substituted in positions 1-, 3-, or 4- have also been electrochemically polymerized (positions 2- and 5- must be free for polymerization). Besides homopolymers, copolymers can also be prepared in this way. Other nitrogen heterocycles that have been polymerized by anodic oxidation include carbazole, pyridazine, indole, and their various substitution derivatives. 

The DszC enzyme was able to convert the following compounds other than DBT thioxanthen-9-one, 2,8-dimethyl DBT, 4,6-dimethyl DBT, and 3,4-benzo DBT. Non-organosulfur compounds such as biphenyl, carbazole, and dibenzofuran did not show any activity. This indicates that dszC specifically recognizes sulfur atom [151]. One study specifically examined the DszC enzyme for oxidation of aryl sulfides [179] and reported oxidation of many sulfides including, naphthyl methyl sulfide, phenyl methyl sulfide, and its alkyl derivatives. 

The results obtained for carbazole degradation by Pseudomonas strain LD2 indicate that carbazole is oxidized initially by angular dioxygenation at position 2, 3 [317] to form 2,9-aminobiphenyl-2,3-diol (via an unstable intermediate), which is further degraded by meta-cleavage of the diol ring to form 2-hydroxy-6-oxo-6-(29-aminophenyl)hexa-2,4-dienoic acid [316], The degradation steps are shown in Fig. 17. 

The reaction network proposed by Ouchiyama et al. for carbazole [316] considers an early oxidation product of degradation to be 2 -aminobiphenyl-2,3-diol. This compound is believed to result from dioxygenase attack at the 1 and 9a positions, resulting in the formation of l,9a-dihydroxy-l-hydrocarbazole. The reaction might be reversed by spontaneous cleavage of the adjacent C—N bond to restore aromaticity and yield back the 2 / -aminobiphenyl-2,3-diol. 

Tricarbonyl(cyclohexadienyl)iron cations react with a variety of nucleophiles to give substituted tricarbonyl(cyclohexadienyl)iron complexes88 with arylamines, N- or C-alkylation can occur depending on the nature of aryl ring substituents. Deligation of C-alkylated arylamines can be achieved by either ferric chloride, which gives the free arylamine, or by iodine in the latter case, cyclization with concomitant oxidation occurs, and carbazoles are produced in moderate yield (Scheme 52).89... 

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