Free radicals carbazole

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). 

A4 (251), B2 (252), B3 (253), B4 (254), and B5 (255) from Streptomyces cyaneus 2007-SVi. The antiostatins represent the first carbazole derivatives with an acetamido group or a substituted urea chain, and exhibited strong inhibitory activity against free radical-induced lipid peroxidation (228) (Scheme 2.62). 

Intramolecular cyclization of diphenylamines to carbazoles is one of the most versatile and practical methods. This has been achieved photochemically, thermally in the presence of elemental iodine at 350°C, or with platinum at 450-540°C, via free radicals with benzoyl peroxide in chloroform, or by using activated metals such as Raney nickel or palladium on charcoal. Most of these methods suffer from low to moderate yields, and, in some cases, harsh reaction conditions (8,480). 

The carbazoquinodns are carbazole-3,4-quinone alkaloids and have been isolated from Streptomyces violaceus 2942-SVS3 [61]. They are strong antioxidative agents and thus represent potential drugs for the treatment of diseases initiated by oxygen-derived free radicals. We have developed an effident synthesis of carbazoquinodn C using palladium(II)-catalyzed oxidative cydization as the key step (Scheme 15.17, Table 15.2) [62]. 

In this paper, we first present a model study on blending a a,co-3,5-dinitrobenzoate PDMS and free 9H-carbazole-9-ethanol, in order to check whether the recently proposed 1 1 stoechiometry between carbazole and dinitrobenzoate molecules indeed applies (Scheme 1). [26] Then, we describe the preparation of triblock copolymers, poly[2-(N-carbazolyl)ethyl methacrylate]-fc-PDMS-fc-poly[2-(N-carbazolyl)ethyl methacrylate] (P(CzEMA)-fe-PDMS-fc-P(CzEMA)), using Atom Transfer Radical Polymerization (ATRP), and their blending with the acceptor-functionalized PDMS. In both studies, the physical association and thermal reversibility of these were followed by different techniques, including UV-Vis spectroscopy, DSC or Rheology. 

The photochemical decomposition of the thiazete 207 in benzene at 30 °C affords carbazole 208190. The reaction presumably involves the formation of a biradical by S—N bond fission which, on loss of S02, undergoes cyclization to yield the final product. Loss of sulphur dioxide also occurs on irradiation of the sultam 209 yielding the quinomethane imine 210, which ring closes to the azetidine 211181. Irradiation of the sulphobenzimide 212 in benzene yields the amide 213 by a free radical reaction path182. 

Poly(vinylcarbazole) is a commercially available polymer prepared by free radical polymerization. Besides excellent photoconductive efficiency, carbazole-based... 

Chuang has also described a manganese(III) acetate initiated oxidative free radical reaction between benzoylindoles 126 and dimethyl malonate which provides faeile access to benzo[b]carbazoles 127 <97H(45)347>. Similar reaction of N-benzoylindoles affords the corresponding indolo[ 1,2-b]isoquinolines. 

The polymerization of A -vinyl carbazole may be initiated by free radicals, by cations, by organometallic catalysts, by charge-transfer processes, or by electrochemical methods. Since the monomer is a solid at room temperature (m.p. 64-66°C, b.p. 154-155°C/3 mm), solid state polymerizations have been carried out both on powdered monomer and on the surfaces of larger crystals. In this process, the reactive species propagates into the interior of the solid. 

H.X. Wu, X.Q. Qiu, R.F. Cai, and S.X. Qian, Poly(N-vinyl carbazole)-grafted multi-walled carbon nanotubes S3mthesis via direct free radical reaction and optical bmiting properties, Appl. Surf. Sci., 253, 5122-5128 (2007). 

Neocarazostatins. The next reported application of inverse-detected 2D NMR to a terrestrial carbazole alkaloid did not appear until 1991 in the report of Kato et al. A series of free radical scavenging compounds, neocarazostatins A-C, were isolated from a Streptomyces sp. strain. The structure of neocarazostatin-A (9) is shown below. Long-range connectivities from an HMBC spectrum (not referenced) were used in assigning the attachments of the two side chains to the carbazole nucleus. 

Solutions of maleic anhydride in ether will initiate cationic polymerizations of isobutyl vinyl ether or Af-vinyl carbazole, if subjected to attacks by free radicals. The same is true if the solutions are irradiated with ultraviolet light or gamma rays. Also, active species are generated from reactions of aldehydes or ketones with maleic anhydride when attacked by free radicals or irradiated by UV light, or gamma rays from These active species are presumed to be formed through... 

Wu HX, Qiu XQ, Cai RE, Qian SX. Poly(A-vinyl carbazole)-grafted multiwalled carbon nanotubes synthesis via direct free radical reaction and optical limiting properties. Appl Surf Sci 2007 253(11) 5122-8. 

In addition to free radical polymerizations, however, cationic and anionic polymerizations may, depending on solvent used, also be observed. The anodic discharge of acetate ions into the homogeneous phase, for example, produces a free radical polymerization of styrene or acrylonitrile. The anodic discharge of perchlorate or boron tetrafluoride ions, on the other hand, leads to the cationic polymerization of styrene, iV-vinyl carbazole, and isobutyl vinyl ether. In contrast, the cathodic decomposition of tertaalkyl ammonium salts induce acrylonitrile to polymerize anionically. 

Carbazole is recovered from bituminous coal tar. Vinylization proceeds at 160-180° C and 20 bar in the presence of ZnO/KOH with acetylene. iV-Vinyl carbazole can be polymerized in suspension with nonoxidizing free radical initiators, and, possibly, also, electron acceptors ... 

Since the antioxidant capacity of carvedilol is be-heved to reside in the carbazole moiety (Yue et al. 1992, 1994, MacKerell jr. et al. 1995), Miglia-VACCA et al. (1998) used 4-methoxycarbazole as a model compound for carvedilol, and 1-hydroxy-and 3-hydroxy-4-methoxycarbazole for its 1- and its 3-hydroxylated metabolites. 1-Hydroxy- and 3-hydroxy-4-methoxycarbazole have good antioxidant activities based of their. 4Habs values. These calculations suggest that both compounds scavenge free radicals via direct H-atom transfer, since their oxyl radical is relatively stable. Hydroxylated carbazole derivatives such as carazostatin and carbazo-mycin show a considerable antioxidant activity, whereas non-hydroxylated carbazoles are inactive (IwATSUKi et al. 1993, Kato et al. 1993). 

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