Synthesis of tricyclic isoindoles and thiazolo[3,2-c][1,3]benzoxazines

The thermolysis of (3R,9bS)-5-oxo-2,3,5,9b-tetrahydrothiazolo[2,3-a]isoindole-3-carboxylic acids in Ac₂O led to novel 3-methylene-2,5-dioxo-3H,9bH-oxazolo[2,3-a]isoindoles and chiral (9bS)-5-oxo-2,3,5,9b-tetrahydrothiazolo[2,3-a]isoindoles were obtained on FVP. Starting from l-cysteine methyl ester (3R,10bR)-5-oxo-2,3-dihydro-10bH-[1.3]thiazolo[3,2-c][1,3]benzoxazines were obtained as single stereoisomers. The thermolysis of (3R,10bR)-5-oxo-2,3-dihydro-10bH-[1.3]thiazolo[3,2-c][1,3]benzoxazine-3-carboxylic acid in Ac₂O gave 5-acetyl-2-phenyl-2,3-dihydrothiazole. The structures of methyl (3R,9bS)-5-oxo-2,3,5,9b-tetrahydrothiazolo[2,3-a]isoindole-3-carboxylate 1a and methyl (2R,4R)-N-chlorocarbonyl-2-(2-hydroxyphenyl)thiazolidine-4-carboxylate 9 were determined by X-ray crystallography.     

AlCl3-promoted three-component cascade reaction for rapid access to [1,2,3]triazolo[5,1-a]isoquinolines

Novel AlCl₃-promoted, three component cascade Henry reaction-triazole formation-intramolecular 6-endo-dig cyclization reactions between 2-alkynylaryl aldehydes, nitroalkanes, and sodium azide for the assembly of [1,2,3]triazolo[5,1-a]isoquinolines have been developed. Further transformations of representative [1,2,3]triazolo[5,1-a]isoquinolines are also described.     

A simple and convenient synthesis of 3-[5-(trifluoromethyl)-1,2,3-triazol-4-yl]cinnamic acids from 4-aryl-6-(trifluoromethyl)-2H-pyran-2-ones and sodium azide

4-Aryl-6-(trifluoromethyl)-2H-pyran-2-ones and ethyl 4-aryl-6-(trifluoromethyl)-2-oxo-2H-pyran-3-carboxylates react with sodium azide to produce highly functionalized CF₃-1,2,3-triazoles: 3-[5-(trifluoromethyl)-1,2,3-triazol-4-yl]cinnamic acids and monoethyl esters of [5-(trifluoromethyl)-1,2,3-triazol-4-yl]arylmethylidene malonic acids.     

Synthesis of π-expanded BODIPYs and their fluorescent properties in the visible-near-infrared region

A series of π-expanded boron-dipyrromethenes (BODIPYs) fused with aromatic rings at β,β-positions, such as benzene, acenaphthylene, and benzofluoranthene were prepared by the reaction of BF₃·OEt₂ with bicyclo[2.2.2]octadiene-fused dipyrromethene and the subsequent retro Diels-Alder reaction. These BODIPYs exhibited the absorptions and the fluorescence emissions over wide range of visible-near-infrared region at 500-800 nm. BODIPYs composed of two fluorantho[8,9-f]isoindoles absorbed and emitted at red-region over 750 nm with absolute fluorescence quantum yield (Φ_f) of ca. 0.3, although they are unstable under air in room light. BODIPY composed fluorantho[8,9-f]isoindole and acenaphtho[1,2-c]pyrrole was stable and showed a bright fluorescence emission at 695 nm with high Φ_f of 0.70.     

Triazolopyridines. Part 24: New polynitrogenated potential helicating ligands

The synthesis of novel 7-{[1,2,3]triazolo[1,5-a]pyridin-3-yl}-[1,2,3]triazolo[1,5-a]pyridines 7, 2-pyridyl-[1,2,3]triazolo[1,5-a]pyrid-7-ylmethanols 11, 3-(6-substituted-2-pyridyl)-[1,2,3]triazolo[1,5-a]pyridines 12, and 7,7′-disubstituted-3,3′-[1,2,3]triazolo[1,5-a]pyridine 20, interesting polynitrogenated ligands as potential helicating compounds or luminescent sensors, from [1,2,3]triazolo[1,5-a]pyridines is described.     

Chemo-, regio- and stereospecific addition of adenine and 8-azaadenine to α,β-acetylenic γ-hydroxy nitriles: a short-cut to novel acyclic adenosine analogues

Adenine (9H-purin-6-amine) adds readily to available α,β-acetylenic γ-hydroxy nitriles under mild conditions (molar ratio 1:1, K₂CO₃, DMF, rt, 10 min) to afford chemo-, regio- and stereospecifically (Z)-3-(6-amino-9H-purin-9-yl)-4-hydroxy-4-alkyl-2-alkenenitriles, novel functionalized acyclic nucleoside analogues (95-98% yield). Under similar conditions (K₂CO₃, DMF, rt, 1 h), 8-azaadenine (3H-[1,2,3]triazolo[4,5-d]pyrimidin-7-amine) reacts with 4-hydroxy-4-methyl-2-pentynenitrile nonselectively at the 7-, 8- and 9-positions to give the corresponding adducts in a 1:10.5:9 ratio, the total yield being 81%. Chemo-, regio- and stereospecific addition of 8-azaadenine to the above α,β-acetylenic γ-hydroxy nitriles leading to (Z)-3-(7-amino-2H-[1,2,3]triazolo[4,5-d]pyrimidin-2-yl)-4-hydroxy-4-alkyl-2-alkenenitriles in 44-90% yield is attained when the reaction is carried out without solvent in the presence of Et₃N (30 mol %), the molar ratio of 8-azaadenine:α,β-acetylenic nitriles being 1:2.0 (rt, 12-38 h).     

[1,2,3]Triazoloazine/(Diazomethyl)azine Valence Tautomers from 5-Azinyltetrazoles

[1,2,3]Triazoloazines are formed by thermolysis of 5-azinyltetrazoles in the gasphase or in solution. Thus, 5-(2-pyridyl)tetrazole ( 7 ) and 5-(2-pyrazinyl)tetrazole ( 11 ) yield [1,2,3]triazolo[1,5-a]pyridine ( 9 ) and [1,2,3]triazolo[1,5-a]pyrazine ( 13 ), respectively, at 400°/10^?3 - 10^?5 Torr. 5-(2-Phenyl-4-quinazolinyl)tetrazole ( 15 ) gives 5-phenyl[1,2,3]triazolo[1,5-c]quinazoline ( 17 ) in 75% yield by heating under reflux in mesitylene solution. 2-(Diazomethyl)pyridine ( 8 ), a valence tautomer of 9 , can be trapped by fumaronitrile, leading to 3-(2-pyridyl)-1, 2-cyclopropanedicarbonitrile ( 19 ). The [1,2,3]triazoloazines undergo base catalysed H/D-exchange in D₂O solution.     

Synthesis of 5-<Emphasis Type="Italic">tert</Emphasis>-butyl-1,2,3-trimethylbenzene catalyzed by [Et<Subscript>3</Subscript>NH]Cl–AlCl<Subscript>3</Subscript>

Common Lewis acids and Lewis acidic ionic liquid catalysts were applied in the synthesis of 5-tert-butyl-1,2,3-trimethylbenzene from 1,2,3-trimethylbenzene and 2-chloro-2-methylpropane, where [Et₃NH]Cl–AlCl₃ demonstrated the most promising catalytic potential. The effects of reaction time, temperature, catalyst composition and dosage have been systematically studied in the presence of [Et3NH]Cl–AlCl3. The maximum selectivity of 90.32% was achieved upon heating at 10°C for 5 h with a mass fraction of [Et₃NH]Cl–AlCl₃ to 1,2,3-trimethylbenzene of 10%. Activity of the ionic liquid catalyst remained high after several cycles.     

Synthesis of some acyclonucleosides with the alkylating chain of acyclovir

The synthesis of some acyclic 1-[1,2,3-triazol-(4 and 5)-ylmethyl]-1H-pyrazolo[3,4-d]pyrimidine nucleosides, via 1,3-dipolar cycloaddition reaction, from 4-substituted N₁-propargyl-1H-pyrazolo[3,4-d]pyrimidines 7a,b and azido derivative 8 is described. Compounds 7a,b and all deprotected acyclic nucleosides 11a,b, 12a,b and 13–22 were evaluated against: HIV-1, HIV-2 and a series of tumour cell-lines. No marked activity was found. Their anti-tuberculosis evaluation showed that compound 7b had marked activity.     

Competing pathways in the photonitrogenation of a 3,5-dihydro-4H/-1,2,3,-triazol-4-one. A novel route to aziridinones

The photodenitrogenation of the 3,5-dihydro-4H-1,2,3,-triazol-4-one 6, obtained from 1-azidoadamantane (5) and the lithium enolate of methyl isobutyrate, produced acetone, the isocyanide 10 and the aziridinone 7, which was solvolysed to the α-methoxy amide 8 during photolysis in [D₄]methanol.     

Quantum chemical study of α-diazocarbonyl bullvalene derivatives and related heterocyclic compounds

According to the results of PBE0/cc-pVTZ quantum chemical calculations, the equilibrium mixture of α-diazocarbonyl bullvalene derivatives (C₁₀H₈N₂O) contains an impurity of the corresponding bullvaleno-[1,2,3]oxadiazoles. The carbonyl group in the major tautomer is conjugated with the three-membered ring. The concentration of other tautomers in the equilibrium mixture of two bullvaleno[1,2,3]selenadiazoles is negligible.     

Synthesis of 1-(1-aryl-1H-1,2,3-triazol-4-yl)-β-carboline derivatives

Reaction of 5-methyl-1-aryl-1H-1,2,3-triazole-4-carbocylic acid chlorides with tryptamine derivatives afforded substituted 1-aryl-N-[2-(1H-indol-3-yl)ethyl]-5-methyl-1H-1,2,3-triazole-4-carboxamides. At heating these compounds in toluene in the presence of POCl₃ and P₂O₅ Bischler-Napieralski cyclization occurs giving 1-(1-aryl-5-methyl-1H-1,2,3-triazol-4-yl)-4,9-dihydro-3H-β-carbolines that can be transformed into β-carboline and tetrahydro-β-carboline derivatives.     

One-pot microwave-assisted solvent-free synthesis,theoretical and experimental studies on barrier rotation of C–N bond of N-alkenyl-1,2,3-triazoles

The reactions on benzotriazoles continue to happen to reach interesting varieties of their derivatives. This study reports a fast one-pot microwave-assisted solvent-free synthesis of N-alkenyl-1,2,3-benzotriazole (3, 5, and 7) and 1-(2-Alkyloxycarbonyl-vinyl)-1H-[1–3] triazole-4-carboxylic acid methyl ester (8 and 9) derivatives by nucleophilic addition reactions of 1,2,3-benzotriazole (C₆H₅N₃) (1) and 1H-[1–3] triazole-4-carboxylic acid methyl ester (C₄H₄N₃O₂) (1′) with R-propiolates (R = Me, Et; 2 & 4) and phenylacetylene 6 in good yields. The values of activation energy for rotation around C–N bond in the synthesized N-alkenyl-1,2,3-triazole compounds were studied by DFT-B3LYP/6-31G* method.     

Stereoselective ring-opening reactions with AcBr and AcCl. A new method for preparation of some haloconduritols

The actions of AcX (X=Br, Cl) on 7-oxa-bicyclo[2.2.1]hept-5-ene-2,3-diol diacetates and a transoid-epoxide prepared from the acetonide of cyclohexa-3,5-diene-cis-1,2-diol were studied. H₂SO₄-catalyzed cleavage of exo-cis-7-oxa-bicyclo[2.2.1]hept-5-ene-2,3-diol diacetate with AcCl gave (1α,2α,3α,6β)-6-chloro-4-cyclohexene-1,2,3-triol triacetate, from which the corresponding chloroconduritol was obtained by trans-esterification (MeOH/HCl). A similar reaction of the exo-diacetate with AcBr in the presence of H₂SO₄ resulted in bromine addition. The formation of bromine from the reaction of AcBr and H₂SO₄ was observed by independent experiments. H₂SO₄-catalyzed reaction of endo-cis-7-oxa-bicyclo[2.2.1]hept-5-ene-2,3-diol diacetate with AcX (X=Br, Cl) gave (1α,2α,3β,6β)-6-halo-4-cyclohexene-1,2,3-triol triacetates. The reaction of the transoid-epoxide with AcX (X=Br, Cl) with no catalyst gave also (1α,2α,3β,6β)-6-halo-4-cyclohexene-1,2,3-triol triacetates.     

Benzo-1,2,3,4-tetrazine 1,3-dioxides annulated with tetraazapentalene systems 3. Annulation at the C(7)—C(8) bond

Thermolysis of 7-azido-8-(2H-1,2,3-triazol-2-y1)-1,2,3,4-benzotetrazine 1,3-dioxide and 7-azido-8-(l H-1,2,3-triazol-l-yl)-1,2,3,4-benzotetrazine 1,3-dioxide afford new heterocyclic systems, viz., 7,11-dehydro-7H, 11H [1,2,3]triazolo[l′,2′:2,3][1,2,3]triazolo[4,5-f]-[1,2,3,4]benzotetrazine 1,3-dioxide and 7,9-dehydro-7 H, 9H [1,2,3]triazolo[2′,1′:2,3]-[1,2,3]triazolo[4,5-f][1,2,3,4]benzotetrazine 1,3-dioxide, respectively, and their thermal stability has been studied.     

Identification of [1,3]dithiolo[4,5-d]dithiazolyl radicals by in situ EPR spectroscopy and cyclic voltammetry

The synthesis of [1,3]dithiolo[4,5-d]dithiazolium salts from readily available zinc chelate has been developed. Chlorination of 2-oxo and 2-(dicyanomethylene) (2-oxo-1,3-dithiole-4,5-diyl) diethanethioates with SO₂Cl₂ followed by condensation with Me₃SiN₃ produced 1,2,3-dithiazolium chlorides. The structure of 5-(dicyanomethylene)[1,3]dithiolo[4,5-d][1,3,2]dithiazol-1-ium tetrafluoroborate was confirmed by powder X-ray diffraction, and its chemical bonding pattern as well as charge transfer were studied within the QTAIM framework applied to the results of plane wave DFT periodic calculations. Reduction with triphenylantimony and electrochemical reduction of [1,3]dithiolo[4,5-d]dithiazolium salts by cyclic voltammetry, chronoamperometry, and microelectrolysis at a controlled potential on a platinum electrode in acetonitrile revealed the formation of [1,3]dithiolo[4,5-d]dithiazolyl radicals, which were characterized by EPR spectroscopy.     

CuSO4/sodium ascorbate catalysed synthesis of benzosuberone and 1,2,3-triazole conjugates: Design,synthesis and in vitro anti-proliferative activity

A novel series of conjugates of benzosuberone and 1,2,3-triazole i.e. 3-(4-phenyl-1H-1,2,3-triazol-1-yl)propyl-9-chloro-2,3-dimethyl-6,7-dihydro-5H-benzo[7]annulene-8-carboxylic acids (8a-j) were synthesized in good to excellent yields catalysed by CuSO₄ under milder reaction conditions and evaluated for their anti-proliferative activity. The structural elucidation of the prepared compounds was carried out using IR, ¹H NMR, ¹³C NMR and Mass spectral analysis. The newly synthesized derivatives (8a-j) were evaluated for their anti-proliferative activity against four human cell lines and the novel derivatives showed moderate to excellent activity. The obtained results suggest that these compounds can be considered as new hits for anti-proliferative drug development programme and further SAR studies can help obtain better anticancer agents.     

Synthesis and structure of benzimidazo[1,2-c][1,2,3]thiadiazoles: first examples of a novel ring system

(1-Amino-1H-benzimidazol-2-yl)methanol 1 with thionyl chloride at reflux afforded 3-chlorobenzimidazo[1,2-c][1,2,3]thiadiazole 4, which reacted with various nucleophiles to give different products depending on the nature of the solvent. The structures of 4 and di(benzimidazo[1,2-c][1,2,3]thiadiazol-3-yl)sulfide 8 were confirmed by single-crystal X-ray analysis.     

Benzothiadiazole vs. iso-Benzothiadiazole: Synthesis,Electrochemical and Optical Properties of D–A–D Conjugated Molecules Based on Them

This paper presents an improved synthesis of 4,7-dibromobenzo[d][1,2,3]thiadiazole from commercially available reagents. According to quantum-mechanical calculations, benzo[d][1,2,3]thiadiazole (isoBTD) has higher values of E_LUMO and energy band gap (E_g), which indicates high electron conductivity, occurring due to the high stability of the molecule in the excited state. We studied the cross-coupling reactions of this dibromide and found that the highest yields of π-spacer–acceptor–π-spacer type compounds were obtained by means of the Stille reaction. Therefore, 6 new structures of this type have been synthesized. A detailed study of the optical and electrochemical properties of the obtained π-spacer–acceptor–π-spacer type compounds in comparison with isomeric structures based on benzo[c][1,2,5]thiadiazole (BTD) showed a red shift of absorption maxima with lower absorptive and luminescent capacity. However, the addition of the 2,2′-bithiophene fragment as a π-spacer resulted in an unexpected increase of the extinction coefficient in the UV/vis spectra along with a blue shift of both absorption maxima for the isoBTD-based compound as compared to the BTD-based compound. Thus, a thorough selection of components in the designing of appropriate compounds with benzo[d][1,2,3]thiadiazole as an internal acceptor can lead to promising photovoltaic materials.     

First identification of benzo[cd]phenanthro[1,2,3-lm]perylene by high-pressure liquid chromatography with ultraviolet-visible spectroscopy and mass spectrometry

Benzo[cd]phenanthro[1,2,3-lm]perylene has been identified as a product of supercritical 1-methylnaphthalene pyrolysis from an experiment performed at 585 °C, 110 atm, and 140 s in a supercritical fluid flow reactor. The identification of benzo[cd]phenanthro[1,2,3-lm]perylene is based on the product's mass spectrum, HPLC elution time, and UV absorbance spectrum. The mass spectrum of the identified 1-methylnaphthalene pyrolysis product, called component I here, reveals a molecular weight of 426, corresponding to a C₃₄H₁₈ polycyclic aromatic hydrocarbon (PAH). The extremely long HPLC elution time, 20–48 min longer than those of the four other C₃₄H₁₈ PAH components in this product mixture, indicates that component I has a planar structure with a high length-to-breadth ratio. Annellation theory is used to interpret and compare the UV spectrum of component I with those of the C₃₀H₁₆ benzo[cd]naphtho[1,2,3-lm]perylene and the C₃₆H₁₈ teropyrene, structures with one ring less and one ring more, respectively, than that of component I. This analysis of component I's UV spectrum, in conjunction with its mass spectrum and HPLC elution behavior, all lead to the identification of component I as the nine-ring PAH benzo[cd]phenanthro[1,2,3-lm] perylene, a molecule whose existence has never before been documented.