Cycloalkano[1″,2″:4,5;4″,3″:4′,5′]bis(pyrrolo[2,3-c]pyrimido[5,4-e]pyridazines): synthesis, structure and mechanism of their formation

Reactions of 3-alkylamino-6,8-dimethylpyrimido[4,5-c]pyridazine-5,7(6H,8H)-diones with cyclohexyl- and cycloheptylamines in the presence of AgPy₂MnO₄ produce novel cycloalkano[1″,2″:4,5;4″,3″:4′,5′]bis(pyrrolo[2,3-c]pyrimido[5,4-e]pyridazines). Detailed information concerning the scope and mechanism of these transformations is discussed.     

Synthesis of pyrido and pyrazinodithienodipyrimidine-4,8(3H,9H)-dione derivatives by the aza-Wittig methodology

A one-pot synthesis of the hitherto unreported pyrido[5″,6″:4,5;3″2″:4′,5′]dithieno[3,2-d:3′,2′-d′]dipyrimidine-4,8(3H,9H)-dione 6a-o and pyrazino[5″,6″:4,5;3″2″:4′,5′]dithieno[3,2-d:3′,2′-d′]dipyrimidine-4,8(3H,9H)-dione 6p-y pentaheterocyclic systems, based on the tandem aza-Wittig heterocumulene-mediated annulation strategy is described.     

The synthesis and properties of ferroceno[1′,2′;1″,2″]bis(1,3-dithiol-2-thione and -2-one) derivatives

The t-butyl and bis(t-butyl) derivatives of hexathia[3.3]ferrocenophane were prepared from the corresponding trithia[3]ferrocenophanes. The former was a mixture of chair-chair and chair-boat isomers, and the latter existed only chair-boat isomer. The hexathia[3.3]ferrocenophanes were led to the tetrathiols with LiAlH₄, which allowed to react with 1,1′-thiocarbonyldiimidazol to give the corresponding ferroceno[1′,2′;1″,2″]bis(1,3-dithiol-2-thione) derivatives. Mono t-butyl and unsubstituted analogs were prepared in a similar manner. The X-ray structural determination showed that these derivatives adopted the conformation in which the 1,3-dithiol-2-thione rings were heaped on top of each other. In the crystal of ferroceno[1′,2′;1″,2″]bis(1,3-dithiol-2-thione), the molecules packed so as to put the axis of molecule in order and to overlap one another above and below. The desulfurizative coupling of the ferroceno[1′,2′;1″,2″]bis(1,3-dithiol-2-thione) derivatives was unsuccessful.     

Au(I)/Ag(I)-catalyzed annulation of sugar aldehyde tethered with 3-phenylprop-2-yn-1-yl ether with aryl amines for the pyrano[4,3-b]quinoline derivatives

Aryl amines undergo smooth annulation with O-phenylpropynyl sugar aldehyde in the presence of the Ph₃PAuCl (10 mol %)/AgSbF₆ (10 mol %) catalytic system to afford the corresponding tetrahydro-3aH-spiro[[1,3]dioxolo[4″,5″:4′,5′]furo[3′,2′:5,6]pyrano[4,3-b]quinoline-2,1′-cyclohexane] derivatives in good yields and selectivity.     

Hybrid inorganic–organic layered structures of [AuCl4] and protonated bipyridyl derivatives

Complexes of [AuCl₄]⁻ with 4,4′-dipyridylethane, 4,4′-dipyridylethene and 4,4′-bipyridine-N,N′-dioxide have been prepared by a solvent layering method. All three complexes pack in distinct organic and inorganic layers: [H₂-dpa][AuCl₄]Cl (1) and [H₂-dpe][AuCl₄]Cl (2) are isostructural and consist of layers of [AuCl₄]⁻ anions alternating with hydrogen-bonded dipyridyl?Cl?dipyridyl layers. In [H-bpdo][AuCl₄] (3), the organic layers consist instead of hydrogen-bonded bipyridyldioxide cations. This structure is the first report of a structure containing protonated 4,4′-bipyridine-1,1′-dioxide.     

Synthesis and photophysics of a novel photocatalyst for hydrogen production based on a tetrapyridoacridine bridging ligand

Molecular photocatalysts allow for selectively tuning their function on a molecular level based on an in-depth understanding of their chemical and photophysical properties. This contribution reports the synthesis and photophysical characterization of the novel molecular photocatalyst [(tbbpy)₂Ru(tpac)PdCl₂]²⁺RutpacPd (with tpac = tetrapyrido[3,2-a:2′,3′-c:3″,2″-h:2?,3?-j]acridine) and its mononuclear building block. Furthermore, detailed photocatalytic activity measurements of RutpacPd are presented. The introduction of the tpac-ligand into the molecular framework offers a potential route to reduce the impact of water as compared to the well-studied class of RutpphzPd (with tpphz = tetrapyrido[3,2-a:2′,3′-c:3″,2″-h:2?,3?-j]phenazine) complexes. The distinct impact of water on the electron-transfer processes in tpphz-ligands stems from the possibility of water to form hydrogen bonds to the phenazine nitrogen atoms and will potentially reduced when replacing the phenazine by the acridine unit. The effect of this structural variation on the catalytic properties and the underlying ultrafast intramolecular charge transfer behavior will be discussed in detail.     

Synthesis, variable temperature NMR investigations and solid state characterization of novel octafluorofluorene compounds

The preparation of a number of new 9-substituted octafluorofluorene derivatives, solution NMR studies, and the first examples of solid state structures of octafluorofluorenes [1,2,3,4,5,6,7,8-octafluorofluorene, C₁₃H₂F₈, 1; 1,2,3,4,5,6,7,8-octafluoro-9-(pentafluoro)phenylfluorene, C₁₉HF₁₃, 8; 1,1′,2,2′,3,3′,4,4′,5,5′,6,6′,7,7′,8,8′-hexadecafluoro-9,9′-bifluorenyl, C₂₆H₂F₁₆, 11] are reported. Variable temperature ¹⁹F NMR investigations have been performed on the 9-aryl substituted compounds 1,2,3,4,5,6,7,8-octafluoro-9-(pentafluoro)phenyl-9-hydroxyfluorene, C₁₉HF₁₃O, 4, 1,2,3,4,5,6,7,8-octafluoro-9-(nonafluoro-4′-biphenylyl)-9-hydroxyfluorene, C₂₅HF₁₇O, 5, and 8, and the energetic barriers to rotation of the aryl have been determined. A lower rotational barrier is observed for compound 4 with respect to compound 8, while 5 does not show fluxional behaviour below 338 K. The results of the variable temperature experiments performed on 8 have been rationalized by 2D NMR studies, and compared to the solid state data resulting from the X-ray structural analysis.     

Synthesis and liquid crystal properties of a novel family of oligothiophene derivatives

In order to develop novel oligothiophene-based liquid crystals capable of hydrogen bonding, new terthiophene derivatives containing an alkylamide group, N,N′-dialkyl-5,5″-dichloro-2,2′:5′,2″-terthiophene-4,4″-dicarboxamide (DNC_nDCl3T, n=8, 18), N,N′-dialkyl-5,5″-dibromo-2,2′:5′,2″-terthiophene-4,4″-dicarboxamide (DNC_nDBr3T, n=5, 8, 16, 18), or N,N′-dialkyl-5,5″-diiodo-2,2′:5′,2″-terthiophene-4,4″-dica-rboxamide (DNC_nDI3T, n=8, 18), were designed and synthesized, and their thermal behaviour was examined. It was found that DNC₁₈DCl3T, DNC₁₈DI3T and DNC_nDBr3T (n=8, 16, 18) form a smectic A phase and that the alkyl chain length greatly affects liquid crystal phase formation. The absence of liquid crystallinity in the corresponding ester derivatives suggests that intermolecular hydrogen bonding also plays a role in the formation of a liquid crystal phases in the DNC_nDBr3T system.     

Synthesis and Ni(0)-catalyzed oligomerization of isomeric 4,4‴-dichloroquaterphenyls

4,4?-Dichloro-1,1′ : 2′,1″ : 2″,1?-quaterphenyl ( 9 ), 4,4?-dichloro-1,1′ : 3′,1″ : 3″,1?-quaterphenyl ( 10 ), and 4,4?-dichloro-1,1′ : 4′,1″ : 4″,1?-quaterphenyl ( 11 ) were synthesized by Pd (0) catalyzed cross-coupling reaction of 4-chlorobenzeneboronic acid with 2,2′-, 3,3′-, and 4,4′-bis (trifluoromethanesulfonyloxy)biphenyl respectively. 4,4?-Dichloro-1,1′ : 2′,1″ : 2″,1?-quaterphenyl ( 9 ) and 4,4?-dichloro-1,1′ : 3′,1″ : 3″,1?-quaterphenyl ( 10 ) were oligomerized by Ni(0) catalyzed homocoupling reaction to yield white and soluble oligophenylenes. © 1993 John Wiley & Sons, Inc.     

Unexpected conversion of a polycyclic thiophene to a macrocyclic anhydride

Oxygenation of 2,5,9,12-tetra(tert-butyl)diacenaphtho[1,2-b:1′,2′-d]-thiophene (1, C₄₀H₄₄S) by peracids gave the cyclic sulfonic ester 4 (2,7,10,13-tetra(tert-butyl)diacenaphtho[1,2-c:1′,2′-e]oxathiin 5,5-dioxide, C₄₀H₄₄O₃S) which, when heated in nitrobenzene, is converted into a complex, macrocyclic anhydride 3 (C₈₀H₈₈O₃), which is derived from two molecules of 4. Further investigation found a likely intermediate in this reaction, 4,4′,7,7′-tetra(tert-butyl)-1,1′-biacenaphthylenylidene-2,2′-dione (5, C₄₀H₄₄O₂), apparently formed from 4 by additional oxidation. Anhydride 3 plausibly arises by Diels-Alder reaction of 4 and 5 followed by several ring fragmentations. The structures of 3, 4, and 5 were unambiguously established by X-ray crystallography.     

Diastereoselective addition of dimethyl phosphite to 3,3′,4,4′-tetramethyl-1,1′-diphosphaferrocene-2-carboxaldehyde

Addition of dimethyl phosphite to racemic 3,3′,4,4′-tetramethyl-1,1′-diphosphaferrocene-2-carboxaldehyde gives almost exclusively one diastereomer of the corresponding α-hydroxyphosphonate (d.r. ?96:4). Its absolute configuration (S, R_p)-(R, S_p) was established by X-ray diffraction.     

Synthesis of substituted 1,1′-diaminoferrocenes from cyclo-2-pentene imines

Condensation of anilines and primary aliphatic amines with 3,4-diphenylcyclo-2-pentenone leads to the corresponding diphenylcyclopentene imines in good yields of 72-90%. Deprotonation of these aminocyclopentadiene tautomers and reaction with FeCl₂ leads to the synthesis of the respective 1,1′-diamino-3,3′,4,4′-tetraphenylferrocenes. Yields increase from 33% to 65% with a decrease in the steric bulk of the amine substituent. The observation that a successful conversion requires two equivalents of base is conceived on the basis of the discussed reaction mechanism. The molecular structure of 1,1′-dianilino-3,3′,4,4′-tetraphenylferrocene (3a), which was determined by single crystal X-ray analysis reveals a trans coordination of the two amine moieties with respect to the central Cp-Fe-Cp axis of the ferrocenyl backbone.     

A series of metal-organic frameworks constructed with arenesulfonates and 4,4′-bipy ligands

Five transition metal compounds containing arenesulfonates and 4,4′-bipy ligands, namely [Zn₂(N,N′-4,4′-bipy)(N-4,4′-bipy)₂(H₂O)₈](bpds)₂ · 5H₂O (1), [Ag₂(N,N′-4,4′-bipy)₂(bpds)] (2), [Cd(N,N′-4,4′-bipy)(H₂O)₄]₂(4-abs)₄ · 5H₂O (3), [Cu(N,N′-4,4′-bipy) (O-bs)₂(H₂O)₂] · 4H₂O (4), and [Zn(N,N′-4,4′-bipy)₂(H₂O)₂](4,4′-bipy)(bs)₂ · 4H₂O (5) (4,4′-bipy = 4,4′-bipyridine, bpds = 4,4′-biphenyldisulfonate, 4-abs = 4-aminobenzenesulfonate, bs = benzenesulfonate), have been synthesized and characterized by X-ray single crystal diffraction, elemental analyses and TG analyses, in order to investigate the coordination chemistry of arenesulfonates and 4,4-bipy, as well as to construct novel coordination frameworks via mixed-ligand strategy. Compounds 2, 4 and 5 could be obtained via hydrothermal or aqueous reactions. Compound 1 forms a binuclear octahedral metal complex. Compounds 2–4 form polymeric chains. Compound 5 consists of 2D square grids with one intercalated 4,4′-bipy molecule. Weak Ag–Ag interactions are observed in compound 2. These complexes show great structural varieties and there are three different coordination modes observed for both the 4,4′-bipy and the sulfonate ligands.     

First rational synthesis of dibenzo[fg,op]naphthacene discotics

A novel, versatile and regiospecific synthesis of variable degree substituted dibenzo[fg,op]naphthacene (also named dibenzopyrene) is described which involves the preparation of a tetraphenyl using a palladium-catalysed cross-coupling of arylboronic acids followed by photochemical cyclization.     

Unexpected cleavage of the Cpy–Cpy bond in the reaction of 2,2′-bipyridine N,N′-diimines with acetylenes

An unusual cleavage of the C_py–C_py bond in the reaction of 2,2′-bipyridine N,N′-diimine and its C-methyl substituted derivatives with acetylenes is described. The effect of the solvent on the yield of 7,7′-bipyrazolo[1,5-a]pyridine-2,2′,3,3′-tetracarboxylates and the products of cleavage of the C_py–C_py bond has been studied. The mechanism of the cleavage reaction is discussed on the basis of DFT calculations.     

O-atom transfer biomimetic oxidation of benzoin in the presence of monooxomolybdenum(IV) thiolate complexes

Novel catalytically active monooxomolybdenum(IV) species containing four thiolate ligands obtainable in solution by NaBH₄ reduction of [Mo^vO(SC₆H₅)₄]⁻, [Mo^vO(Z-cys-Val-OMe)₄]⁻, (Z=benzyloxycarbonyl), or [Mo^vO(S₂C₆H₄)₂]⁻ perform the pyridine-N-oxide oxidation of benzoin in N,N-dimethylformamide at 30 °C. The order of catalytic activity is [Mo^vO(Z-cys-Val-OMe)₄]⁻ > [Mo^vO(S₂C₆H₄)₂]⁻ > [Mo^vO(SC₆H₅)₄]⁻ ([benzoin]/[oxidant]/[catalyst]= 20/20/1), while the oxidation by air under the same catalytic conditions gives a different order, [Mo^vO(Z-cys-Val-OMe)₄]⁻> [Mo^vO(SC₆H₅)₄]⁻ >[Mo^vO(S₂C₆H₄)₂]⁻. During the catalytic cycle in the amine-N-oxide oxidation, two intermediate species, [Mo^IVOL₄]²⁻ and [Mo^VIO₂L₄]²⁻, were detected by ¹H NMR, while in the air oxidation an unidentified Mo(VT) species is involved.     

Solution-processed red iridium complexes based on carbazole-phenylquinoline main ligand: Synthesis, properties and their applications in phosphorescent organic light-emitting diodes

New carbazole-phenylquinoline (CVz-PhQ) based iridium complexes were designed and synthesized for their application in red phosphorescence organic light-emitting diodes (PhOLEDs) and their photophysical, electrochemical and electroluminescence (EL) properties were investigated. The PhOLEDs were fabricated using bis[9-(2-(2-methoxyethoxy)ethyl)-3-(4-phenylquinolin-2-yl)-9H-carbazolato-N,C2′]iridium 2-pyrazinecarboxylic acid (EO-CVz-PhQ)₂Ir(prz) and bis[9-(2-(2-methoxyethoxy)ethyl)-3-(4-phenylquinolin-2-yl)-9H-carbazolato-N,C2′]iridium 5-methyl-2-pyrazinecarboxylic acid (EO-CVz-PhQ)₂Ir(mprz) as the emitter and PVK, co-doped with OXD-7 as the electron transport material and TPD as the hole transport material, as the polymer host. The red emissive PhOLEDs, based on the ITO/poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS)/4,4′,4″-tris(carbazole-9-yl)triphenylamine (TCTA)/poly(N-vinylcarbazole) (PVK):N,N′-diphenyl-N,N′-(bis(3-methylphenyl)-[1,1-biphenyl]-4,4′-diamine (TPD):1,3-bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazole-2-yl]benzene (OXD-7):Ir complex/cathode configuration, exhibited a maximum external quantum efficiency of 3.68% and a maximum luminance efficiency of 6.69 cd/A. Furthermore, by introducing a TCTA interlayer, the PhOLEDs showed only a slight efficiency roll off of 5.4% from a low current density (1.81 mA/cm²) to a high current density (44.59 mA/cm²).     

Dimerization of 2-pyridylisonitriles produces π-extended fused heteroarenes useful as highly selective colorimetric and optical probes for copper ion

A very simple synthesis of pyrido[2″,1″:2′,3′]imidazo[4′,5′:4,5]imidazo[1,2-a]pyridines 2 was achieved from the dimerization of 2-pyridylisonitriles. The optical responses of these π-extended fused heteroarenes to a series of metal ions were investigated by means of UV-visible absorption spectrum in acetonitrile. It was found that most of compounds 2 selectively responded to Cu²⁺, and the limit of detection was about 3.5×10⁻⁷ M when using the best probe, 3,9-dimethylpyrido[2″,1″:2′,3′]imidazo[4′,5′:4,5]imidazo[1,2-a]pyridine 2d. Meanwhile some compounds 2 specifically showed a color change from colorless to red or yellow when they are exposed to copper ion in acetonitrile, whereas other transitional, alkali and alkaline earth metal ions could not induce a color change. This work not only established a direct access to π-extended fused heteroarenes, but also supplied novel sensitive and selective colorimetric and optical probes for copper ion.     

Syntheses of C-substituted icosahedral dicarbaboranes bearing the 8-dioxane-cobalt bisdicarbollide moiety

The treatment of 1,2-, 1,7- and 1,12-carbaborane lithiated isomers with [3,3′-Co-8-(CH₂CH₂O)₂-(1,2-C₂B₉H₁₀)-(1′,2′-C₂B₉H₁₁)] (1) at molar ratios 1:1 or 1:2 at room temperature in THF leads generally to the formation of a series of orange double-cluster mono and dianions. These were characterized by NMR and MS methods as [1′′-X-1′′,2′′-closo-C₂B₁₀H₁₁]⁻, [2]⁻; [1′′-X-1′′,7′′-closo-C₂B₁₀H₁₁]⁻, [3]⁻ and [1′′-X-1′′,12′′-closo-C₂B₁₀H₁₁], [4]⁻ for the monoanions, whereas [1′′,2′′-X₂-1′′,2′′-closo-C₂B₁₀H₁₀]²⁻, [2]²⁻; [1′′,7′′-X₂-1′′,7′′-closo-C₂B₁₀H₁₀]²⁻, [3]²⁻; and [1′′,12′′-X₂-1′′,12′′-closo-C₂B₁₀H₁₀]²⁻, [4]²⁻ for the dianions (where X = 3,3′-Co-8-(CH₂CH₂O)₂-(1,2-C₂B₉H₁₀)-1′,2′-(C₂B₉H₁₁)). Moreover, these borane-cage subunits can be easily modified via attaching variable substituents onto cage carbon and boron vertices, which makes these compounds structurally flexible potential candidates for BNCT of cancer and HIV-PR inhibition.     

Metal complexes of 2-aza-2-benzyl-5,10,15,20-tetraphenyl-21-carbaporphyrin: M(2-NCH2C6H5NCTPP) (M = Ni, Pd) and Mn(2-NCH2C6H5NCTPP)Br (NCTPP = N-confused 5,10,15,20-tetraphenyl porphyrinate)

The crystal structures of (2-aza-2-benzyl-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N,N′,N″) nickel(II) methylene chloride solvate [Ni(2-NCH₂C₆H₅NCTPP); 4], (2-aza-2-benzyl-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N,N′,N″) palladium(II) [Pd(2-NCH₂C₆H₅NCTPP); 5] and bromo(2-aza-2-benzyl-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N,N′,N″) manganese(III) toluene solvate [Mn(2-NCH₂C₆H₅NCTPP)Br·C₆H₅CH₃; 3·C₆H₅CH₃] have been established. The coordination sphere around the Ni²⁺ ion in 4 (or Pd²⁺ ion in 5) is distorted square planar (DSP), whereas for Mn³⁺ in 3·C₆H₅CH₃, it is a square-based pyramid with the Br atom lying in the axial site. The g value of 11.34, measured from parallel polarization of the X-band EPR spectra at 4 K, is consistent with a high spin mononuclear manganese(III) centre (S = 2) in 3. The magnitude of the axial (D) zero-field splitting (ZFS) for the mononuclear Mn(III) centre in 3 was determined approximately to be 1.4 cm⁻¹ by paramagnetic susceptibility measurements and conventional EPR spectroscopy.