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The effective approaches for regioselective double formylation and acetylation of 5,12-dialkyl-6,7-diaryl-substituted 5,12-dihydroindolo[3,2- a ]carbazoles by their treatment with dichloromethyl methyl ether in the presence of SnCl 4 or with acetyl chloride in the presence of AlCl 3 to afford the 2,9-diformyl or 2,9-diacetyl derivatives, respectively, were developed. Furthermore, new 2,9-bis(2,2-dicyanovinyl) derivatives were synthesized by the Knoevenagel condensation of diformyl-containing substrates with malononitrile, when new 2,9-bis(quinoxaline-2-yl)- and 2,9-bis(benzo[ g ]quinoxaline-2-yl) derivatives were formed via microwave-promoted oxidation of diacetyl-containing substrates with SeO 2 to the corresponding diglyoxals, followed by the reaction of these intermediates with o -phenylendiamine or 2,3-diaminonaphthalene, respectively. The basic optical and electrochemical properties of some 5,12-dihydroindolo[3,2- a ]carbazoles were investigated.

Two new classes of heteroacenes, namely benzo[4′,5′]thieno[2′,3′:4,5]thieno[3,2-b]quinolines and benzo[4′,5′]thieno[2′,3′:4,5]thieno[3,2-b][1,8]naphthyridines, have been formed using the Friedlander reaction to annulate the benzo[b]thieno[2,3-d]thiophene scaffold to quinoline or 1,8-naphthyridine fragments. In accordance with this synthetic strategy, benzo[b]thieno[2,3-d]thiophen-3(2H)-ones were treated with 2-aminobenzaldehydes or 2-aminonicotinaldehyde in the presence of pyrrolidine in glacial acetic acid at reflux to give the desired quinoline- or 1,8-naphthyridine-fused compounds, respectively. The optical and electrochemical properties of selected heteroacenes were determined.

A number of 5, 11-dialkyl-6, 12-di(hetero)aryl-5, 11-dyhydroindolo[3, 2-b]carbazoles has been synthesized by modified method based on HBr catalyzed condensation of (hetero)aromatic aldehydes with indole in MeCN solution affording 5, 6, 11, 12-tetrahydroindolo[3, 2-b]carbazoles, that have been aromatized with I2 in DMF solution for 1 h at reflux, followed by alkylation of 5, 11-dihydro compounds. New 2, 8-dicyano-(10 examples) as well as 2, 8-bis(benzo[d]thiazol-2-yl)-substituted (5 examples) derivatives of these 5, 11-dyhydroindolo[3, 2-b]carbazoles have been obtained through their initial C2, 8-formylation, followed by treatment of dialdehydes with excess of hydroxylamine and dehydration of the formed aldoximes with acetic anhydride or by interaction with excess of 2-aminothiophenol in DMSO solution, respectively. © 2018 Arkat. All rights reserved. This research study was supported financially by the Russian Science Foundation (Project No. 16-13-10435).

A new 5,11-dihydroindolo[3,2-b]carbazole-based bidentate ligand bearing two carboxylic groups, (3,3′-(indolo[3,2-b]carbazole-5,11-diyl)dipropionic acid, H2icdc), has been synthesized in two steps and then used for the construction of two metal–organic coordination polymers, namely [Zn3(dmf)2(icdc)3]·4DMF (1) and [Zn2(dabco)(icdc)2]·4NMP·4H2O (2) (dabco = 1,4-diazabicyclo[2.2.2]octane, DMF = N,N-dimethylformamide, NMP = N-methyl-2-pyrrolidone). Compound 1 has a layered structure, while compound 2 has a 3D framework structure. Both compounds display linker-based blue fluorescence.

A series of new 5,11-dihydroindolo[3,2-b]carbazole derivatives, containing functional thiophene, 2,2′-bithiophene or 2,2′:5′,2″-terthiophene moieties at both C-2 and C-8 positions of their fused scaffolds, have been obtained from 2,8-diacetyl-substituted 5,11-dihydroindolo[3,2-b]carbazole compounds through the effective strategy, which is based on the sequence of two reactions, namely the Vilsmeier–Haack formylation and the Fiesselmann thiophene synthesis. The starting acetyl substituted materials have been transformed into the corresponding 3-chlorocrylaldehyde-containing compounds by treatment with POCl3-DMF complex, followed by the reaction with alkyl thioglycolates or α-mercaptoacetone in the presence of triethylamine to afford 2-carboalkoxythiophene- or 2-acetylthiophene-linked derivatives. 2-Acetylthiophene derivatives have further been involved into the same sequence of reactions to obtain 2,2′-bithiophene-, and 2,2′:5′,2″-terthiophene-linked 5,11-dihydroindolo[3,2-b]carbazole compounds.

A new general approach to double nitration of 6,12-di(hetero)aryl-substituted and 6,12-unsubstituted 5,11-dialkyl-5,11-dihydroindolo[3,2-b]carbazoles by acetyl nitrate has been developed to obtain their 2,8-dinitro and 6,12-dinitro derivatives, respectively. A formation of mono-nitro derivatives (at C-2 or C-6) from the same indolo[3,2-b]carbazoles has also been observed in several cases. Reduction of 2-nitro and 2,8-dinitro derivatives with zinc powder and hydrochloric acid has afforded 2-amino- and 2,8-diamino-substituted indolo[3,2-b]carbazoles, while reduction of 6,12-dinitro derivatives under similar reaction conditions has been accompanied by denitrohydrogenation of the latter compounds into 6,12-unsubstituted indolo[3,2-b]carbazoles. Formylation of 6,12-dinitro derivatives has proved to occur only at C-2, while bromination of these compounds has taken place at both C-2 and C-8 of indolo[3,2-b]carbazole scaffold. Moreover, 6,12-dinitro-substituted indolo[3,2-b]carbazoles have been modified by the reactions with S- and N-nucleophiles. Notably, the treatment of 6,12-dinitro compounds with potassium thiolates has resulted in the displacement of both nitro groups, unlike potassium salts of indole or carbazole, which have caused substitution of only one nitro group.

A series of new polycyclic compounds bearing the 5,11-dihydroindolo[3,2-b]carbazole ring system, as the common motif of their nine-ring scaffolds, has been successfully prepared with the usage of an efficient two-step strategy, based on the double Friedel–Crafts acylation of 5,11-dihexyl-6,12-di(hetero)aryl-substituted 5,11-dihydroindolo[3,2-b]carbazoles with 2-iodobenzoyl chloride in the presence of SnCl4, followed by regioselective palladium-catalyzed cyclization of the obtained 2,8-bis(2-iodobenzoyl) derivatives into the desired fused 9H-fluoren-9-ones. Some modifications of these nine-ring structures have been performed to afford compounds of the same family bearing the 9H-fluorene fragments. Basic photophysical and electrochemical properties as well as thermal stability of the new fused indolo[3,2-b]carbazole derivatives have been determined.