RuCl3/SnCl2 mediated synthesis of pyrrolo[2,3-c]carbazoles and consequent preparation of indolo[2,3-c]carbazoles

A simple method for the synthesis of pyrrolo[2,3-c]carbazoles from N-alkylated-3-aminocarbazole derivatives and ethylene glycol has been developed via heteroannulation reaction using RuCl₃/SnCl₂ system. Moreover indolo[2,3-c]carbazoles were prepared from various pyrrolo[2,3-c]carbazoles in good yields.     

Synthesis of indolo[2,3-c]quinolines from 3-arylindole-2-ketoximes

Treatment of the 2,4-dinitrophenyl ethers of some 3-arylindole-2-ketoximes with base results in a cyclisation reaction to yield indolo[2,3-c]quinolines.     

Thiadiazole fused indolo[2,3-a]carbazoles as new building blocks for optoelectronic applications

New indolo[2,3-a][1,2,5]thiadiazolo[3,4-c]carbazoles including functional groups (halide or hydroxyl groups) on the meta positions relative to the nitrogen atoms which are known to be the most conjugated, have been synthesized following two synthetic routes. The characterizations of their optical and electrochemical properties evidence their potential as new building blocks for optoelectronic materials.     

Reduction of indolo[2,3-b]quinoxalines

Reduction of indolo[2,3-b]quinoxalines with zinc in the presence of an anhydride gave N,N-diacyl trapped 6,11-dihydroindolo[2,3-b]quinoxalines in 43-92% yields. When the reduction with zinc was performed in TFA/TFAA, an unexpected ring opened product was isolated in 49% yield. The structure of this product could be identified as 1,2-dihydro-1-trifluoroacetyl-3-[(2-trifluoroacetylamino)phenyl]quinoxaline.     

Selenopheno[3,2-c]- and [2,3-c]coumarins: Synthesis,cytotoxicity, angiogenesis inhibition,and antioxidant properties

A simple method for the synthesis of substituted selenopheno[2,3-c] and -[3,2-c]coumarins by treatment of the corresponding ethynylcoumarins with in situ prepared selenium(IV) bromide in 1,4-dioxane-water was elaborated. Molecular structures for selected derivatives were confirmed by X-ray diffraction measurements. The cytotoxic activity of novel selenophenocoumarins showed higher activity and lower acute toxicity than sodium selenite on various tumor cell lines as well as an ability for inhibiting matrix metalloproteinases (MMP-1 – MMP-14), angiogenesis on matrigel in vitro and in vivo. The compounds exhibit antioxidant and prooxidant properties.     

Heterocycles [h]-fused onto 4-oxoquinoline-3-carboxylic acid, Part VI [1]. Synthesis and X-ray structure of model indolo[3,2-b]- and [2,3-b]pyrido[2,3-f]quinoxaline-3-carboxylic esters

Cyclocondensation reaction of ethyl 7,8-diamino-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylate with 1-methylisatin produced a separable mixture of the corresponding indolo[3,2-b]- and [2,3-b]pyrido[2,3-f]quinoxaline-3-carboxylates, of which the latter isomer predominates. On the other hand, interaction with 1H-isatin or 5-chloroisatin gave the respective indolo[2,3-b]pyrido[2,3-f]quinoxaline-3-carboxylates as the sole regiospecific products. The structures of these new pentacyclic derivatives are based on microanalytical, spectral (IR, MS, and NMR) and X-ray crystal structure data.     

Polyazasteroids II.. 1,2,4-Triazolol[3′,4′:2,3]pyrimido[4,5-c]quinolin- 11(12H)ones,imidazo[2′,1′:2,3]pyrimido[4,5-c]quinolin-11(12H)ones and 2,3-dihydroimidazo[2′,1′:2,3] pyrimido[4,5-c]quinolin-11(12H)ones

Starting with 2-substituted quinoline-3,4-dicarboxylic acids, a series of substituted 1,2,3,4-tetrahydropyrimido[4,5-c]quinolinone-3-thiones were obtained. The latter compounds were converted to the three novel polyazasteroid series: 1,2,4-Triazolo[3′,4′:2,3]pyrimido[4,5-c]-quinolin-11(12H)ones, imidazo[2′,1′:2,3]pyrimido[4,5c]quinolin-11(12H)ones and 2,3-dihydroimidazo[2′,1′:2,3]pyrimido[4,5-c]quinolin-11(12H)ones. The intermediate 3-hydrazino-1,2-dihydropyrimido[4,5-c]quinolinones and nitrous acid gave the 3-azido derivatives rather than the tetrazolo compounds.     

A rapid access to indolo[2,1-a]pyrrolo[4′,3′:4,5]pyrano[5,6-c]coumarin/[6,5-c]chromone derivatives by domino Knoevenagal intramolecular hetero Diels-Alder reactions

Knoevenagal condensation of indole-2-carbaldehyde containing an internal dienophile with coumarins, followed by domino intramolecular hetero Diels-Alder reaction, provides polycyclic heterocycles. Different approaches for stereo- and chemoselective synthesis of indolo[2,1-a]pyrrolo[4′,3′:4,5]pyrano[5,6-c]coumarin and indolo[2,1-a]pyrrolo[4′,3′:4,5]pyrano[6,5-c]chromone derivatives are described.     

Ligand‐Controlled Palladium(II)‐Catalyzed Regiodivergent Carbonylation of Alkynes: Syntheses of Indolo[3,2‐c]coumarins and Benzofuro[3,2‐c]quinolinones

Regiodivergent syntheses of indolo[3,2‐c]coumarins and benzofuro[3,2‐c]quinolinones through a controllable palladium(II)‐catalyzed carbonylative cyclization are established. The chemo‐ and regioselectivity are exclusively tuned by the ligand on the palladium catalyst. The rigid framework of the electron‐deficient ligand promotes the O‐attack/N‐carbonylation cyclization leading to benzofuro[3,2‐c]quinolinones, while a sterically bulky and electron‐rich ligand facilitates N‐attack/O‐carbonylation cyclization to generate indolo[3,2‐c]coumarins. Furthermore, various other nucleophiles are applicable for delivering a variety of indoloquinolinones, pyranoquinolones, and chromeno[3,4‐c]quinolinones in one step, and serves as a method for creating compound libraries for drug discovery.     

The synthesis of [1]benzothieno[2,3-c]quinolines, [1]benzothieno[2,3-c][1,2,4]triazolo[4,3-a]quinoline,and [1]benzothieno[2,3-c]tetrazolo[1,5-a]quinoline

Photocyclization of 3-chloro-N-phenylbenzo[b]thiophene-2-carboxamide 10 afforded [1]benzothieno[2,3-c]-quinolin-6(5H)-one 11 which was chlorinated to 6-chloro[1]benzothieno[2,3-c]quinoline 12 followed by dechlorination to give [1]benzothieno[2,3-c]quinoline 5 . A series of 6-substituted alkoxy and thioalkoxy[1]benzothieno[2,3-c]quinoline derivatives were prepared along with the N-methyl quaternary salt 13 of 5 . 6-Chloro[1]-benzothieno[2,3-c]quinoline 12 was converted into 6-hydrazino[1]benzothieno[2,3-c]quinoline 23 which upon treatment with formic acid yielded [1]benzothieno[2,3-c][1,2,4]triazolo[4,3-a]quinoline 6 . Treatment of 23 with nitrous acid resulted in [1]benzothieno[2,3-c]tetrazolo[1,5-a]quinoline 7 . Compounds 6 and 7 are novel heterocyclic ring systems.     

RhIII-catalyzed annulation of N-methoxyindozamides with heterobicyclic alkenes towards indolo[3,2-c]heteroarenes

A rhodium-catalyzed annulation protocol towards indolo[3,2-c]-1-azaanthraenes and successive treatment with different acids, which offered diverse indolo[3,2-c]-heteroarenes, were herein demonstrated. The transition metal-mediated system offered a direct and facile approach towards the heterocyclic compounds of great significance, enjoying high efficiency and good functional groups compatibility.     

Triazole-fused indolo[2,3-a]carbazoles: synthesis,structures, and properties

The synthesis, structure, and photophysical and electrochemical properties of triazole fused indolo[2,3-a]carbazole derivatives 2 - 5 are reported. The key step involved in the synthesis of triazole fused indolo[2,3-a]carbazole derivatives is the Cadogan ring closing reaction. 2-Hexyl-5,6-dinitro-2H-benzo[d][1,2,3]triazoles having 4,7-diaryl capping were subjected to the Cadogan cyclization reaction to obtain compounds 2-5 . In contrast to thiadiazole-fused indolo[2,3-a]carbazole 1 , bromination of triazole-fused indolo[2,3-a]carbazole 4 afforded only meta-dibrominated product with respect to the nitrogen of fused pyrrole rings on treatment with both N-bromosuccinimide (NBS) and elemental bromine. These compounds showed positive solvatochromism in their emission spectra. Incorporation of electron-donating substituent in the indole moiety resulted in the elevation of the highest occupied molecular orbital (HOMO) level. Density functional theory (DFT) calculations were performed to support the experimental findings.     

A convenient approach to the design and synthesis of indolo[3,2-c]coumarins via the microwave-assisted Cadogan reaction

3-(4,5-Dimethoxy-2-nitrophenyl)coumarins bearing various substituents on the benzene ring of the coumarin system have been prepared from salicylaldehydes and 2-(4,5-dimethoxy-2-nitrophenyl)acetonitrile by means of the Perkin condensation. Further cyclization of these 3-aryl coumarins through the microwave-assisted Cadogan reaction afforded the corresponding indolo[3,2-c]coumarins in good to excellent yields.     

Synthesis of novel indolo[2,3-c]quinolinones via Ugi-4CR/palladium-catalyzed arylation

In this letter, an expedient method was developed for the construction of novel indolo[2,3-c]quinolinone derivatives via palladium-catalyzed arylation of Ugi adducts obtained from the reaction of indole-2-carboxylic acid, various aromatic aldehydes, 2-bromoanilines, and isocyanides. The reaction proceeded efficiently with various starting materials to produce the indoloquinolinone scaffolds in good yields.     

Microwave assisted synthesis of indolo[2,3-b]dibenzo[b,g][1,8]naphthyridines

We have developed an effective microwave assisted p-TsOH catalyzed synthesis of indolo[2,3-b]dibenzo[b,g][1,8]naphthyridines via a one pot reaction of 3-amino-9-ethylcarbazole and 2-chloro-3-formylquinolines.     

Synthesis of 2,3′-biindolyls and indolo[3,2-a]carbazoles

Several highly activated 2,3′-biindolyls were prepared from methyl 5,6-dimethoxyindole-2-carboxylate and oxindoles. The 2,3′-biindolyls were further transformed into a hydroxy indolo[3,2-a]carbazole and a bisindole amide.     

The synthesis of monomethoxy[1]benzothieno[2,3-c]quinolines

A series of monomethoxy[1]benzothieno[2,3-c]quinolines 24-28 were prepared by photocylization of the appropriate 3-chloro-N-phenylbenzo[b]thiophene-2-carboxamides 9–13 to [1]benzothieno[2,3-c]quinolin-6(5H)-ones 14-18 followed by chlorination to 6-chloro[1]benzothieno[2,3-c]quinolines 19-23 then dechlorination resulting in the title compounds except for 25 which was achieved by direct reduction of 15 . Reaction of 24-28 with methyl iodide provided the corresponding N-methyl quaternary salts 29-33 . Also, conversion of 4-meth-oxy[1]benzothieno[2,3-c]quinolin-6(5H)-one 16 to 4-methoxy-6-methylthio[1]benzothieno[2,3-c]quinoline 35 and 4,6-dimethoxy[1]benzothieno[2,3-c]quinoline 36 is described.     

A facile one-pot highly chemo- and regioselective synthesis of the novel heterocyclic system indolo[1,2-c]azolo[1,5-a]quinazoline-8,10-dione

A series of novel indolo[1,2-c]azolo[1,5-a]quinazoline-8,10-diones was obtained by a multi-component reaction between cyclic 1,3-diketones, α-aminoazoles, and glyoxal. The unexpected cyclization process was established by NMR spectroscopy and X-ray diffraction measurements.     

A practical approach to the fused β-carboline system. Asymmetric synthesis of indolo[2,3-a]indolizidinones via a diastereoselective intramolecular α-amidoalkylation reaction

Fused β-carboline systems, as indolo[2,3-a]indolizidinones, indolo[2,3-a]quinolizidinones, their 2-oxa analogues, and benzo[a]indolo[2,3-a]indolizidinones are prepared efficiently via an RLi addition-N-acyliminium ion cyclisation sequence on readily available imides. In an enantioselective variant of these α-amidoalkylation reactions, the addition of MeLi to a chiral non-racemic imide derived from tryptophan yielded an oxo amide, which was cyclised diastereoselectively upon treatment with BF₃·OEt₂, to afford 5,11b-trans-indoloindolizidinone in moderate yield and high ee (99%).     

New formal (3+3) cycloaddition of enaminones for forming tetracyclic indolo[2,3-b]quinolines under microwave irradiation

Concise and efficient base-promoted domino formal (3+3) cycloaddition has been established for the formation of tetracyclic indolo[2,3-b]quinoline derivatives under microwave heating. The present methodology shows attractive properties, such as the maximum efficiency of a process, short reaction periods, and operational simplicity, and it can avoid time-consuming and costly syntheses, tedious work-up and isolation of intermediate. This chemistry provides a facile and promising synthetic strategy to construction of tetracyclic indolo[2,3-b]quinoline skeleton.