Carbazoles substitution

The Graebe-Ullman carbazole synthesis is normally carried out in sealed tubes and at high temperature. The carbazoles/substituted carbazoles are obtained in general in poor to moderate yields. ... 

This section covers the total synthesis of simple tricyclic carbazoles which are not covered in Sections ILA.1-II.A.5, and includes the tricyclic carbazoles substituted either at the C-ring or at the 9 N)- of the carbazole nucleus. 

Chloranil in boiling xylene has been shown to be an excellent dehydrogenation agent for the preparation of carbazoles from 1,2,3,4-tetrahydro-carbazoles (75-95%). By this procedure, carbazoles substituted in the 1-, 2-, and 3-positions with alkyl, halo, alkoxyl, carboxyl, or nitro groups are readily made. The starting materials are available by ring closures of cyclohexanone-OT-phenylhydrazones. A palladium-carbon catalyst for the same purpose is also noteworthy, the yields of alkylcarbazoles being 86-100%. ... 

Copper-mediated coupling reactions of / -iodocalixarenes with phthalimide followed by hydrazinolysis should be mentioned as an alternative and independent strategy to obtain p-aminocalixarenes . The carbazole-substituted derivatives 50 (Figure 8) were obtained similarly by Ulhnan coupling . CMPO derivatives (51c), urea compounds (51b), available also via the isocyanates (51a), may be mentioned additionally. Mono- (52) and diimides with acidic functions pointing towards the cavity, and the calix[6]arene-based acetylcholine esterase mimic (53) are more sophisticated examples. 

Fig. 22a-d. Examples of polymers used in photorefractive composites a poly (vinylcarbazolc) (PVK) b carbazole substituted polysiloxarie (PSX) c poly(methylmethacrylate-co-tricy-clodecylmethacrylate-co-N-cyclohexylmaleimide-co-benzyl methacrylate) (PTCB) d thioxanthene containing polymer (P-THEA)... 

On the other hand, formation of photorefi active silicone composite with good performance was reported A carbazole-substituted polysiloxane that was sensitized by 2,4,7-trinitro-9-fluorenone was used as a photoconducting medium and l-[4-(2-nilrovinyl)phenylpiperidine was added as an optically nonlinear chromophore. The photorefractive property of polymer was determined by diffraction efficiency using a 100 pm-thick film. The maximum diffraction efficiency (rj max) of 71% was obtained at the electric field of 70 V/pm. 

Recently, D-A-based ter- and quaterthiophenes 2.82 (w = 1, 2) (Chart 1.18) endowed with A-ethylcarbazole and cyanoacrylic acid at each terminus were prepared for their utilization as the active component in dye-sensitized solar cells (DSSCs) [163]. Coupling of the Grignard reagent of 2-bromo-3-hexylthiophene and 3-iodo-9-A-ethylcarbazole yielded carbazole-substituted thiophene. 

It is interesting to note that striae have also been observed in certain polymer solutions stressed by shear between glass plates [2-8]. Marcher et al. [10] observed these patterns in carbazole-substituted helical poly-amino acid solutions stressed by shear. These workers used Fourier transform infrared spectroscopy to calculate order parameters describing the degree of alignment and packing of the carbazole side chains. 

Figure 9.13 Total absorption coefficient of single crystalline DCH (a carbazole-substituted polydiacetylene) obtained by Kramers-Kronig analysis of 8 K reflection data. The broken portion reflects transitions of the carbazole chromophore. is the profile of the transition leading to charge carrier formation, cn, refers to the exciton transition. The broken portion of the Ot curve reflects sensitized carrier generation via side-group excitation. Eg is the band gap inferred from electroabsorption work (see Reference 4). (From Bassler, H., in Polydiacetylenes, Bloor, D. and Chance, R. R., Eds., M. Nijhoff, Dordrecht, 1985, 135. With permission.)...

Comparing our results with other published reports it is clear that removal of carbazole moiety from polymer backbone by any kind of spacer group eliminates the formation of excimer emission sites. This applies even to bomopolymers of the rather rigid carbazole-substituted styrenes 11 and 12... 

In the first instance, poly-a-amino acids with carbazole-substituted side chains were chosen for this purpose. Poly-a-amino acids are well known to be capable of forming lyotropic cholesteric phases due to their a-helical conformation. The formation of a homeotropic nematic phase, as shown schematically in Fig. 10, would give the desired morphology with the stacking of the carbazole rings in the plane of the cell. This is in essence the same morphology obtained with the carbazole-doped thermotropic... 

Dewar and his co-workers, as mentioned above, investigated the reactivities of a number of polycyclic aromatic compounds because such compounds could provide data especially suitable for comparison with theoretical predictions ( 7.2.3). This work was extended to include some compounds related to biphenyl. The results were obtained by successively compounding pairs of results from competitive nitrations to obtain a scale of reactivities relative to that of benzene. Because the compounds studied were very reactive, the concentrations of nitric acid used were relatively small, being o-i8 mol 1 in the comparison of benzene with naphthalene, 5 x io mol 1 when naphthalene and anthanthrene were compared, and 3 x io mol 1 in the experiments with diphenylamine and carbazole. The observed partial rate factors are collected in table 5.3. Use of the competitive method in these experiments makes them of little value as sources of information about the mechanisms of the substitutions which occurred this shortcoming is important because in the experiments fuming nitric acid was used, rather than nitric acid free of nitrous acid, and with the most reactive compounds this leads to a... 

There are reports of an increasing number of palladium-assisted reactions, in some of which the palladium has a catalytic function. Thus furan and thiophene undergo facile palladium-assisted alkenylation giving 2-substituted products. Benzo[6 Jfuran and TV- acetyl-indole yield cyclization products, dibenzofurans and carbazoles respectively, in addition to alkenylated products (8UOC851). The arylation of pyrroles can be effected by treatment with palladium acetate and an arene (Scheme 86) (81CC254). 

Pyrano[3,2-g]benzoxazine, dihydrosynthesis, 3, 714 Pyranobenzoxazines synthesis, 6, 190 Pyranobenzoxazoles mass spectra, 3, 615 Pyrano[2,3-a]carbazoles synthesis, 4, 235 Pyrano[2,3- 6]carbazoles synthesis, 4, 235 Pyrano[3,2-a]carbazoles synthesis, 4, 235 Pyranochromones synthesis, 3, 821 Pyranochromones, dihydrosynthesis, 3, 81 817 Pyranocoumarins crystal data, 3, 623 mass spectra, 3, 610 Pyranodipyranones synthesis, 3, 794 Pyrano[3,2-6]indol-4-ones synthesis, 4, 302 Pyran-2-ol, dihydrodehydration, 3, 762 Pyran-2-ol, 3-methyltetrahydro-synthesis, 3, 775 Pyran-2-ol, tetrahydro-6-substituted synthesis, 3, 775 Pyran-4-ol, tetrahydro-IR spectra, 3, 594 Raman spectra, 3, 594 Pyranols, tetrahydro-bond lengths, 3, 621 synthesis, 3, 777... 

The Graebe-Ullman carbazole synthesis has been enmloyed in the preparation of substituted carbolines, as well as indolo[2,3-i] quinolines, which are often difficult to synthesize via other approaches, for example, the Fischer indole process. 

The indol-3-yl-substituted indolo[2,3-()]carbazole 143 has been isolated as a product from the complex mixture generated by the decomposition of urorosein (144) (99CHE561). Interestingly, when subjected to alkylation conditions involving sodium hydride and dimethyl sulfate in THF, 143 was transformed into the N. -dimethyl derivative 145 in 36% yield (00MI2). 

The trifluoromethyl derivative 146 has been obtained as a minor product from the reaction of (l-methyhndol-3-yl)methanol with trifluoroacetic acid anhydride (TFAA), the major product (22% yield) being 6-trifluoromethylindolo[3,2-()]-carbazole [98LTC(B)841]. Several substituted indolo[2,3-()]carbazoles have also been encountered during studies on the reaction of 4,6-dimethoxyindole with... 

Similarly, iV,A/ -dimethyl-3,3 -bisindolylmethane (169) has been used in a related experiment, where treatment thereof with trifluoroacetic fflihydride (TFAA) in diethyl ether at room temperature yielded a mixture of products from which the trifluoromethyl-substituted indolo[3,2-b]carbazole 170 was isolated as the major pentacyclic component, accompanied by the hydroxy derivative 171 as well as small amounts of the indolo[2,3-h]carbazole 146 (Scheme 20). The precursor 169 could also be prepared in situ from A-methylindol-3-methanol under... 

Several derivatives of indolo[3,2-fi]carbazole, such as the system 185, have been claimed to arise from the reaction of suitably substituted simple indoles on treatment with thallium triacetate in acetic acid. A compound having the purported structure of 185 was thus isolated when 2,3-dimethylindole was used as the substrate [78UC(B)422]. Many years later, it was demonstrated that this product is in fact a derivative of indolo[2,3-c]carbazole (cf. Section VI) (99T12595). 

Studies on the Bischler-Napieralski cyclization of A -acetyltryptamine in the presence of indole have led to the isolation of numerous products, among which the indolocarbazole 186 could be found in 3.5% yield. This outcome was rationalized as a result of the intermediacy of a spiroindolenine species formed under these conditions [89H(28)175]. During detailed studies on the polymerization of indole, formation of a low yield of the related indolo[3,2-h]carbazole 187 was discovered in the product mixture originating from the treatment of indole with p-toluenesulfonic acid at elevated temperature [88JCS(P1)2387]. In an investigation of the condensation of p-benzoquinone with 4-substituted anilines, an indolo[3,2-h]carbazole derivative has been reported to be formed in 2% yield (80JOC1493). 

The most recent synthetic efforts in this area have focused on the preparation of mono- and diformyl-substituted indolo[3,2-l)]carbazoles 202 and 203, which are potent aryl hydrocarbon receptor (AHR) ligands (cf. Section V,C). 

Dibenzofuran and carbazole gave yields of 69 and 80%, respectively, of the phosphinated derivative, but the position of substitution was not determined. ... 

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