Dibenzo pyrroles

In summary, all estimates of resonance energies indicate a decrease in aromaticity in the sequence benzene > thiophene > pyrrole > furan. Similar sequences are also found for the benzo[6] and dibenzo analogues. A somewhat different sequence is found for the benzo[c] fused heterocycles with isoindole > benzo[c]thiophene > benzo[c]furan. As would be anticipated, the resonance energies for the benzo[c] heterocycles are substantially lower than those for their benzo[6] isomers. 

Methyl-3-(10,11-dihydro-5H-dibenzo[a,d]cycloheptene-5-ylidene)-1 -pyrrol ine Ethyl iodide Sodium borohydride... 

Whereas the degradation of the carboxylates of the monocyclic furan, thiophene, and pyrrole is initiated by hydroxylation, degradation of their benzo analogs is generally carried out by dioxygenation. The degradation of the analogs dibenzofuran and dibenzo-[l,4]-dioxin is discussed in Part 2 of this chapter. 

The syntheses shown in Scheme 26 (71CB1573) are based on dibenzo-/3-tropolone (108) and its enamines. Condensation of 108 and benzoin in the presence of ammonia affords pyrrole 109. The morpholino enamine gives pyrazole 110 via benzoylation, hydrolytic elimination of morpholine, and cyclization, whereas diazo-group transfer onto the anilino enamine leads to triazole 111. Dione 108 and p-nitrophenylazide in one step give predominantly the p-nitro derivative of 111 (92G249). 

Dipolar cycloaddition is another route to benzopyrrolo[l,2-a]azepines by pyrrole ring formation. The azomethine ylide derived from imine 88 and difluorocarbene adds to DMAD to produce dimethyl 3-fluoro-9H-dibenzo[c,/]-pyrrolo[l,2-fl]azepine-l,2-dicarboxylate 89 in 20% yield (Equation (12)... 

Most of the polymer modifications incorporating benzo-substituted pyrroles have been done with the dibenzo derivative, carbazole, primarily because of its well-known photocon-ductive properties. The modification reaction often involves a substitution reaction on some halogenated polymer. This substitution reaction can be quite facile. Poly(vinylbenzyl chloride), for example, reacts with the potassium salt of carbazole in DMF to yield the carbazole-functional polymer in 97% yield (76MI11110). 

Menon presented a set of interesting liquid crystals 48 (Scheme 25) based on dibenzo[18]crown-6 modified with 2-hydroxy-3-methoxybenzene (48a), 3,4,5-trimethoxybenzene (48b), thiophene (48c), and pyrrole (48d) linked via a Schiff base [63]. All compounds are lacking long alkyl chains in the periphery. Nonetheless, broad mesophases with different geometries (SmC, SmA, N) were observed. 

A theoretical study of the acidity (proton loss) of the porphyrin 266 and some related systems was carried out by means of the B3LYP/6-31+G(d,p) computational level. These include, on one hand, porphyrin fragments 267 and pyrrole 11 (X = H) and the monoanion and dianion of 266 and, on the other hand, chalcogen-related porphyrins 268,269, and 270 and their anions, as well as cyclic nitrogen derivatives 271, 272, 273, and 274, simplified models of porphyrin, dibenzo[14]annulene, phthalocyanine, and porphycene. 

Systems considered are the parent heterocycles with one heteroatom (furan, thiophene, selenophene, and pyrrole), their monoaza and polyaza derivatives, and the monobenzo derivatives of the above systems. Dibenzo derivatives such as dibenzofuran and carbazole are not taken into account, since they have no position in the five-mem bered ring susceptible to electrophilic attack. Likewise, no consideration is given to more complicated systems, formed by the fusion of two heterocyclic rings such as thienothiophenes or pyrrolopyridines, for which, in any case, no quantitative work is available. 

R. Goutarel, Bull. Soc. Chim. France pp. 769-774 (1960). Carbazoles (dibenzo[6,d]pyrrole), V-vinylcarbazole ... 

Novel classes of fused pyrroles, dibenzo[2,3 6,7]oxepino[4,5- ]pyrroles and dibenzo[2,3 6,7]thiepino[4,5- ]pyrroles, were prepared by the intermolecular cyclocondenation of dibenzo[2,3 6,7]oxepin-5-ones and dibenzo[2,3 6,7]thiopin-5-ones with (dimethylhydrazono)acetaldehyde <07JHC1129>. 

SYNS 9-AZAFLUORENE 9H-CARBAZOLE DIBENZOPYRROLE DIBENZO(b,d)PYRROLE DIPHENYLENEIMINE DIPHENYLENIMIDE DIPHENYLENIMINE USAF EK-600... 

Dibenzo[Z),e ]thiepinones are reductively ring opened at the benzylic C-S bond [194] anthrone and anthraquinone are among the products. The cleavage and ring closure are akin to those observed in the reduction of 2-phenyl-l,3-thiazin-6-ones to 3-hydroxy-pyrroles [195]. 

Since damotepine (257) was found to show sedative activity <66NEP6514187>, a variety of modified dibenzo[ /]thiepines have been prepared and their physiological activities have been researched. Zotepine (258) has psychosedative and antipsychotic activity <78CPB3058>. Citatepine (259) was found to have neuroleptic, psychosedative activity, and to be a potential dopamine antagonist. <83EUP125484>. A lH-dibenzo[2,3 6,7]thieno[4,5-c]pyrrole derivative (260) (CGP-19865) was... 

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