Quantum-chemical study of triindolylmethylium salts dissociation in comparison with triphenyl-methyl chloride and its derivatives

Quantum-chemical calculations have been carried out of heterolytic dissociation energies of a series of tri(1H-indol-3-yl)methylium compounds with different counter-ions within the framework of density functional theory, using the functional B3LYP in the basis 6-31 + G(d). The results obtained have been compared with data calculated for unsubstituted triphenylmethane derivatives (triphenylmethylium chloride and methanesulfonate) and also for tri(4-dimethylaminophenyl)methylium chloride (crystal violet). Ionicity of tri(indol-3-yl)methylium salts is compared with that of crystal violet chloride and triphenylmethane derivatives.     

Synthesis and photovoltaic properties of new thieno[3,2-b]indole-based dyes

Russian Chemical Bulletin - New dyes of the 3-[5-(4-alkyl-4H-thieno[3,2-b]indol-2-yl)thiophen-2-yl]-2-cyanoacrylic acid series were prepared based on 2-(thien-2-yl)-substituted thieno[3,2-b]indole...     

Zeolite-catalyzed synthesis of nicotinyl-fused indolo-pyrazoles and evaluation of their activities against Anopheles arabiensis and Lipoxygenase

A series of nicotyl-fused indolo-pyrazoles (NFIPs) were synthesized by a one-pot multicomponent reaction of aryl aldehydes, isoniazid, and indole in the presence of zeolite as a catalyst. Structures of all the synthesized compounds were established by IR, ¹H-NMR, ¹³C-NMR, 2D-NMR, TOF-MS, and elemental analysis. The products were obtained in excellent yields and high purity. All 10 compounds were screened for larvicidal and insecticidal properties against Anopheles arabiensis and tested for their lipoxygenase inhibitory activity. Compounds (3-(3-hydroxy-4-methoxyphenyl)-2,3-dihydropyrazolo[4,3-b]indol-1(4H)-yl)(pyridin-4-yl)methanone ( 4i ) and (3-(3-bromo-5-hydroxy-4-methoxyphenyl)-2,3-dihydropyrazolo[4,3-b]indol-1(4H)-yl)(pyridin-4-yl)methanone ( 4j) displayed highest larvae mortality at a 4 μg/ml dose in 24 h. Compounds (3-(4-methoxyphenyl)-2,3-dihydropyrazolo[4,3-b]indol-1(4H)-yl)(pyridin-4-yl)methanone ( 4h ) and (3-(3-hydroxy-4-methoxyphenyl)-2,3-dihydropyrazolo[4,3-b]indol-1(4H)-yl)(pyridin-4-yl)methanone ( 4i ) showed a significant knockdown activity after 24 h with 70% mortality. Furthermore, (3-(4-chlorophenyl)-2,3-dihydropyrazolo[4,3-b]indol-1(4H)-yl)(pyridin-4-yl)methanone ( 4c ) and (3-(3-bromo-5-hydroxy-4-methoxyphenyl)-2,3-dihydropyrazolo[4,3-b]indol-1(4H)-yl)(pyridin-4-yl)methanone ( 4j ) displayed promising lipoxygenase inhibitory activity with a mortality of 70% and 60%, respectively.     

Alkaloids from Arundo donax. XVI. Structure of the New Dimeric Indole Alkaloid Arundavine

The new bis-indole alkaloid arundavine, a tryptamine-tryptamine base, was isolated from roots of Arundo donax. The dimer consists of monomeric units of two known indole alkaloids, alline and bufotenine, joined through the N1 and C4′ atoms, respectively, to give the structure 8-[3-(2-dimethylaminoethyl)-5-hydroxy-1H-indol-4-yl]-1-methyl-2,3,8,8a-tetrahydro-1H-pyrrolo[2,3-b]indol-3a-ol.     

Thermal ring contraction of dibenz[b,f]azepin-5-yl radicals: new routes to pyrrolo[3,2,1-jk]carbazoles

Flash vacuum pyrolysis (FVP) of N-allyl- or N-benzyldibenz[b,f]azepine at temperatures from 750 to 950 degrees C gives pyrrolo[3,2,1-jk]carbazole as the major product. The mechanism of the ring contraction involves dibenzazepin-1-yl radical formation, followed by transannular attack and formation of a 2-(indol-1-yl)phenyl radical which cyclizes. The mechanism is supported by independent generation of 2-(indol-1-yl)phenyl radicals by two different methods, and the use of 1-(2-nitrophenyl)indole as a radical generator gives an optimized synthetic route to pyrrolo[3,2,1-jk]carbazole (54% overall yield in two steps from indole). The first substituted pyrrolo[3,2,1-jk]carbazoles have been synthesized by FVP methods and also by reactions of the parent compound with electrophiles, leading to a range of 4-substituted pyrrolocarbazoles.     

1,1-Disubstituted-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indolecarboxylic acid esters and ketones. The base catalyzed transformation of 1-(2′,3′,4′,9′-tetrahydrospiro[cyclohexane-1,1′-[1H]pyrido[3,4-b]indol]-2-yl)alkanones into 2-(4,9-dihydro-3H-pyrido[3,4-b]indol-1-yl)-1 -alkylcyclohexanols

Condensation of 1H-indole-3-ethanamines 1 with cyclic β-keto esters 2 under azeotropic conditions followed by acid-catalyzed ring closure of the resulting enamines 3 gave 2′,3′,4′,9′-tetrahydrospiro[piperidine-3,1′,-[1H]pyrido[3,4-b]indole] -4-carboxylic acid alkyl esters 4 . Condensation of 1 with 2-acylcycloalkanones 8 gave two types of enamines, 10 and 11 , respectively. Enamines 10 on treatment with acid gave 1-(2′,3′,4′,9′-tetrahydro-3H-pyrido[3,4-b]indol-1-yl)-1-alkylcyclohexanols 17 . Compounds 17 were further dehydrated to give cycloalkane derivatives 19.     

Synthetic anthracyclines: regiospecific total synthesis of a D-ring indole analogue of daunomycin

The 4-methoxy-5-methylpyrano[4,3-b]indole-1,3(4H,5H)-dione (9), prepared from methyl 3-methoxycarbonyl-1-methylindol-2-yl acetate (6), underwent a strong base-induced cycloaddition reaction with 2-chloro-6,6-ethylenedioxy-5,6,7,8-tetrahydro-1,4-naphthoquinone (11) to give the tetrahydronaphtho[2,3-b]carbazole-7,12-dione (10), regioselectively. The cycloadduct (10) was successfully converted to a D-ring indole analogue of daunomycin (1a).     

The synthesis of 3,4,4a,9a-tetrahydro-2(1H)-carbazolones

Cyclization of 4-(1-methylindol-3-yl)-2-butanone and the corresponding 1-benzyl analog in trifluoroacetic acid furnishes 9-methyl- and 9-benzyl-3,4,4a,9a-tetrahydro-2(1H)-carbazolone, respectively. Under the same conditions, 4-(indol-3-yl)-2-butanone gives the dimer, 3-(3-oxo-butyl)-2-[3-(3-oxobutyl)-2-indolinyl] indole. When boron trifluoride etherate is used instead of trifluoroacetic acid, the desired 3,4,4a,9a-tetrahydro-2(1H)-carbazolone is obtained. The determination of the structure of the tetrahydrocarbazolones is described and the stereochemistry of the ring fusion is discussed.     

Synthesis of pyrrolo[1,2-a]indoles: vilsmeier formylation of some 3-methylindol-2-yl ketones and 3(3-methylindol-2-yl)propenoic ester

3-Methylindol-2-yl methyl ketone reacted with phosphoryl chloride in dimethylformamide to give 3-chloro-3(3-methylindol-2-yl), propenal (4). 2-Carbomethoxy- and 2-carbethoxy-1-chloro- 9H-pyrrolo[1,2-a]indol-9-ylidene acetaldehyde (10a and b) were formed by reaction with the same reagent of 3(3-methylindol-2-yl) propenoate (7) and 3(3-methylindol-2-yl)-3-oxopropanoate (2) respectively. In the latter case, 2-carbethoxy-1-chloro-3-dimethylamino-9-methyl-3H-pyrrolo[1,2-a]indole (9b) was isolated as an intermediate. The structure of the pyrroloindolylidene acetaldehydes was proved by synthesis of the chromophore from 4-acetyl-3-methyl-1-phenyl-pyrrole-2-carboxylate (26). The preparation and behaviour of 1-phenylpyrrole-2,4- and 3,4-dicarboxylates, monomethylated in the pyrrole ring, is described. These compounds were prepared during a search for a satisfactory route to a starting material for the synthesis of compounds related to 10a and b. The saponification of such diesters is remarkably selective, and in the case of the 2,4-dicarboxylates, contradicts accepted generalisations concerning the lability of pyrrole α,β-diesters to selective hydrolysis.     

Tris(1-alkylindol-3-yl)methylium salts as a novel class of antitumor agents

Tris(1-alkylindol-3-yl)methanes were obtained and oxidized into tris(1-alkylindol-3-yl)methylium salts. The resulting salts are more toxic to cultured tumor cells than to non-tumor ones. The cytotoxicity of tris(1-alkylindol-3-yl)methylium salts depends on the length of the substituent at the N atom of the heterocycle, increasing from an N-unsubstituted derivative toward N-butyl- and N-pentyl derivatives. A further increase in the length of the N-alkyl substituent lowers the cytotoxicity. The cytotoxicity of tris(1-alkylindol-3-yl)methylium salts for tumor cells correlates with their antibacterial and antifungal activity. Tris(1-alkylindol-3-yl)methylium salts produced a cytocide effect on Gram-positive microorganisms and the most active compounds, on Gram-negative microorganisms as well. Similar patterns of the structure—activity relationship of N-alkylated tris(indol-3-yl)methylium derivatives, which was observed for various lines of tumor cells, bacteria, and fungi, suggest the general character of the mechanisms of the death of prokaryotic and eukaryotic cells induced by these compounds.     

Co2(CO)8-catalyzed intramolecular hetero-Pauson-Khand reaction of alkynecarbodiimide: synthesis of (+/-)-physostigmine

[reaction: see text] Herein we describe a novel Co(2)(CO)(8)-catalyzed intramolecular aza-Pauson-Khand-type reaction of alkynecarbodiimide derivatives affords pyrrolo[2,3-b]indol-2-one ring systems in reasonable yields. This is the first reported Co(2)(CO)(8) successfully applied in the hetero-Pauson-Khand reaction. Significantly, the transformation of one of our pyrrolo[2,3-b]indol-2-one derivatives into the indole alkaloid, (+/-)-physostigmine, was completed in a highly stereoselective manner.     

A new method for the synthesis of [1,4]diazepino[6,5-b]indole derivatives

Reactions of 3-[(N-aryl-N-chloroacetyl)amino]-2-formylindoles with substituted anilines gave 1,4-diaryl-2-oxo-1,2,3,6-tetrahydro[1,4]diazepino[6,5-b]indol-4-ium chlorides and those with 4-aminopyridine yielded 4-amino-1-(1-aryl-2-oxo-2,5-dihydro-1H-pyrido[3,2-b]indol-3-yl)pyridinium chlorides. Reduction of 1,2,3,6-tetrahydrodiazepinoindol-4-ium chlorides afforded the corresponding hexahydro derivatives. An alternative synthesis of 1-(4-nitrophenyl)-3-oxo-4-phenyl-1,2,3,4,5,6-hexahydro[1,4]diazepino[6,5-b]indole from 3-[N-(4-nitrophenyl)amino]-2-[(phenylimino)methyl]indole was developed. The method involves the following sequence of transformations: reduction, chloroacetylation, and intramolecular alkylation. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2193–2199, December, 2006.     

Three-Component Reactions of 3-Arylidene-3H-Indolium Salts,Isocyanides and Amines

A multicomponent reaction of isocyanides with aryl(indol-3-yl)methylium salts and amines has been found. A series of aryl(indol-3-yl)acetimidamides was obtained in up to 96% yields. In the case of ethyl isocyanoacetate, the reaction is followed by cyclization to form 3,5-dihydro-4H-imidazol-4-one derivatives.     

Anion binding properties of indolylmethanes

The anion binding properties of the indolylmethanes (1) were investigated by ¹H-NMR spectroscopy in CDCl₃. Tris(3-methylindol-2-yl)methane (1a) selectively bound a chloride anion the over other tested anions (Br^?, I^?, HSO ₄ ^? , and NO ₃ ^? ). In contrast, analogous compounds, phenyl bis(3-methylindol-2-yl)methane (1b), 2-hydroxyphenyl bis(3-methylindol-2-yl)methane (1c), tri(indol-3-yl)methane (1d), and phenyl di(indol-2-yl)methane (1e), showed a low anion binding ability and selectivity. These results indicate that the number and a position of the binding sites (indole NH protons) of the indolylmethanes are important factors for the formation of the complex with an anion. The high binding ability and selectivity of 1a toward a chloride anion is attributed to the proper size of the binding pocket for a chloride anion and the formation of multiple hydrogen bonds between the three indole NH protons and a chloride anion. The anion affinity of 1a was significantly affected by the cation component of quaternary ammonium salts, indicating that it is ion pair binding and not solely anion binding.     

Regioselectivity of cyclization of 3-allyl(propargyl)sulfanyl-5<Emphasis Type="Italic">H</Emphasis>-[1,2,4]triazino[5,6-<Emphasis Type="Italic">b</Emphasis>]indoles

The interaction of 3-allylsulfanyl-5H-[1,2,4]triazino[5,6-b]indole with iodine led to 1-iodomethyl-1,2-dihydro[1,3]thiazolo[2',3':3,4][1,2,4]triazino[5,6-b]indol-11-ium pentaiodide with an angular structure, on the basis of which 1-iodomethyl-1,2-dihydro[1,3]thiazolo-, 1-methylidene-1,2-di-hydro[1,3]thiazolo, and 1-methyl[1,3]thiazolo derivatives were obtained. The intramolecular cyclization of 3-propargyl(allyl)sulfanyl-5H-[1,2,4]triazino[5,6-b]indoles under the influence of concentrated sulfuric acid led to linear annelated products:3-methyl[1,3]thiazolo[3',2':2,3][1,2,4]tri-azino[5,6-b]indole or its 2,3-dihydro derivative.     

Reaction of 1,5-diaryl-3-hydroxy-4-methylsulfonyl-3-pyrrolin-2-ones with urea,hydrazine, ethylenediamine,and <Emphasis Type="Italic">o</Emphasis>-phenylenediamine

With urea 1,5-diaryl-3-hydroxy-4-methylsulfonyl-3-pyrrolin-2-ones form the 3-amino derivatives of pyrrolones. In reactions with hydrazine hydrate and ethylenediamine the corresponding salts are formed. With ethylenediamine at 180–185°C the double salt of 3-hydroxy-4-methylsulfonyl-1,5-diphenyl-3-pyrrolin-2-one forms N,N′-di(4-methylsulfonyl-1,5-diphenyl-3-pyrrolin-2-on-3-yl)-ethylenediamine. The reaction with o-phenylenediamine gives 2,3-diaryl-4-methylsulfonylpyrrolo-[2,3-b]quinoxalines. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, 1631–1636, November, 2007.     

Diastereoselective pot-and atom-economical synthesis of densely-substituted polycyclic 1,2- and 1,2,3-fused indole scaffolds

A simple, efficient, one-pot sequential process for the preparation of a family of 8,9-dihydropyrido[1,2–a]indol-6(7H)-one scaffolds in acceptable yields has been established under mild conditions. The Michael-hemiaminalization-oxidation reaction proceeds between methyl 2-(3-formyl-1H-indol-2-yl) acetate and trans-β-aryl/alkyl-substituted acroleins using pyrrolidine-BzOH as an efficient organocatalyst, followed by oxidation of in situ generated of C,N-fused hemiaminal adducts in the presence of PDC at room temperature. Excitingly, organobase-catalyzed highly diastereoselective (up to ≤9:1 dr) construction of a series of pharmacologically attractive 1,2,3-fused tetracyclic indole scaffolds with five contiguous chiral centers including an all-carbon stereogenic center has been realized through our developed method. Moreover, pyrrolidine-BzOH and PTSA as combined catalytic systems promote the uninterrupted sequential Michael-cyclization reaction, followed by N-alkylation reaction with carbazole to produce interesting class of 6-(9H-carbazol-9-yl)-6,7,8,9-tetrahydropyrido[1,2–a]indole derivatives in a diastereoselective manner.     

Synthesis of hexahydropyrrolo[2,3-b]indole alkaloids based on the aza-Pauson-Khand-type reaction of alkynecarbodiimides

Upon treatment with 30 mol % of Co2(CO)(8) and 30 mol % of TMTU in toluene at 70 degrees C, benzene-bridged alkynecarbodiimides efficiently underwent a ring-closing reaction to give the pyrrolo[2,3-b]indol-2-ones in good yields. These conditions could nearly suppress the formation of the urea derivatives, which were consistently observed when 10 mol % of Co2(CO)(8) and 60 mol % of TMTU in benzene were used. The synthesis of the eight hexahydropyrrolo[2,3-b]indole alkaloids was accomplished from the resulting pyrrolo[2,3-b]indol-2-ones via the introduction of an angular substituent at the C(3a)-position by treatment with NaBH(4)/alkyl bromide as the crucial step.     

Synthesis and reactions of 1-benzyl-3-haloalkyl-5-chloropyrazoles

Synthesized 1-benzyl-3-chloroalkyl-5-chloropyrazoles reacted with indole and pyrrole in DMSO in the presence of alkali to give 3-(heter-1-yl)alkyl-substituted 1-benzyl-5-chloropyrazoles. 1-[(1-Benzyl-5-chloropyrazol-3-yl)methyl]indole reacted regiospecifically with chloroal trifluoromethylsulfonyl- and 4-chlorophenylsulfonylimines providing the products of C-amidotrichloroethylation into the position 3 of the indole ring. {1-[(1-Benzyl-5-chloropyrazol-3-yl)methyl]indol-3-yl}sulfanylacetic acid was obtained by the reaction of 1-[(1-benzyl-5-chloropyrazol-3-yl)methyl]-indole with iodine, thiourea, and chloroacetic acid.     

Structures and photochromic properties of fulgides based on naphtho[1,2-<Emphasis Type="Italic">b</Emphasis>]furan and benzo[<Emphasis Type="Italic">g</Emphasis>]indole

The novel heterocyclic fulgides, i.e. 3-isopropylidene-4-{1-[5-methoxy-1-(4-methoxy-phenyl)-2-methyl-1H-benzo[g]indol-3-yl]ethylidene}dihydrofuran-2,5-dione and 3-isopropylidene-4-[1-(1-benzyl-5-methoxy-2-methyl-1H-benzo[g]indol-3-yl)ethylidene]dihydrofuran-2,5-dione, were prepared and isolated as E-isomers. Photochromism, E-configuration, and high resistance to photocoloration—photobleaching of solutions of these fulgides as well as 3-isopropylidene-4-[1-(5-methoxy-2-methylnaphtho[1,2-b]furan-3-yl)ethylidene]dihydro-furan-2,5-dione and 3-isopropylidene-4-[1-(5-methoxy-2-methyl-1-phenyl-1H-benzo[g]indol-3-yl)ethylidene]dihydrofuran-2,5-dione synthesized previously were shown by X-ray diffraction analysis, ¹H NMR spectroscopy and electronic absorption spectroscopy. The novel fulgides show fluorescence and high thermal stability of photogenerated cyclic form. Repeated photo-coloration—photobleaching is accompanied by reversible photoinduced E—Z isomerization. Benzo[g]indolyl fulgides are characterized by the longer wavelength absorption of both original (E) and photoisomeric cyclic (C) forms as compared to naphthofuran fulgide.