Iodo-substituted triphenylene-based discogens: by metal-mediated oxidative cross-coupling

New monoiodopentakis(alkoxy)triphenylene derivatives were synthesized and characterized. The metal-mediated oxidative coupling of 2-iodoalkoxybenzene with 3,3',4,4'-tetraalkoxybiphenyl by MoCl₅ as oxidizing reagent yields 2-iodopentakis(alkoxy)triphenylene. These products were purified by repeated column chromatography; their liquid crystalline properties were studied by polarizing optical microscopy and differential scanning calorimetry. All the derivatives exhibit a columnar mesophase over a wide temperature range.     

Vanadium oxytrichloride,a novel reagent for the oxidative trimerization of o-dialkoxybenzenes to hexaalkoxytriphenylenes

Triphenylene derivatives with six peripheral chains can make excellent discotic liquid crystals showing great promise in electronic devices. Vanadium oxytrichloride was found to be a novel reagent for the preparation of various triphenylene derivatives. Symmetrically substituted hexaalkoxytriphenylenes were obtained from o-dialkoxybenzenes by oxidative trimerization with VOCl₃ in high yields. Oxidative coupling of a 3,3',4,4'-tetraalkoxybiphenyl with 1,2-dialkoxybenzenes yielded unsymmetrically substituted derivatives of triphenylene; a direct coupling of a 3,3',4,4'-tetraalkoxybiphenyl with alkoxyphenol produced monofunctionalized triphenylenes.     

Iodo‐substituted triphenylene‐based discogens: by metal‐mediated oxidative cross‐coupling

New monoiodopentakis(alkoxy)triphenylene derivatives were synthesized and characterized. The metal‐mediated oxidative coupling of 2‐iodoalkoxybenzene with 3,3′,4,4′‐tetraalkoxybiphenyl by MoCl₅ as oxidizing reagent yields 2‐iodopentakis(alkoxy)triphenylene. These products were purified by repeated column chromatography; their liquid crystalline properties were studied by polarizing optical microscopy and differential scanning calorimetry. All the derivatives exhibit a columnar mesophase over a wide temperature range.     

Novel hexasubstituted triphenylene discotic liquid crystals having three different types of peripheral substituent

The synthesis and mesomorphic properties of a variety of novel hexasubstituted triphenylene derivatives having three different types of peripheral substitutions are described. Monobromination of 2,3,6,7-tetrakis(pentyloxy)triphenylene 4 , prepared by Suzuki coupling of 2-iodo-3',4,4',5-tetrakis(pentyloxy)biphenyl 2 and phenylboronic acid followed by cyclization, yields 10-bromo-2,3,6,7-tetrakis(pentyloxy)triphenylene 5 . Nucleophilic aromatic displacement of the bromine with the potassium salt of pentanethiol, followed by bromination, yields 2-bromo-6,7,10,11-tetrakis(pentyloxy)-3-(pentylsulphanyl)triphenylene 7 having a bromo, thioalkyl and alkoxy-substituted periphery of the triphenylene nucleus. The reaction of 7 with copper(I) cyanide gives the cyanotriphenylene derivative 8 , while palladium-copper catalysed alkynylation of 7 results in the synthesis of the substituted alkyne derivative 9 . The deprotected alkyne 10 was converted to dimer 11 where two molecules of a monothioalkyl-tetra-alkoxytriphenylene are connected via a rigid pi-conjugated diacetylene bridge. Compounds 7 , 8 , 9 , 10 form hexagonal columnar phases while the dimer 11 shows a discotic nematic phase.     

Method for the determination of three toxic non-ortho chlorine substituted coplanar PCBs in environmental samples at part-per-trillion levels

A method has been devised combining alkali digestion, carbon chromatography and high-resolution gas chromatography for the determination of 3,3',4,4'-tetra, 3,3',4,4',5-penta, and 3,3',4,4',5,5'-hexachlorobiphenyl, the biologically active congeners of PCBs and approximate isostereomers of 2,3,7,8-TCDD. This method permits determinations of parts-per-trillion levels of these toxic residues in biological samples. Interference both from biogenic and from xenobiotic substances was reduced to extremely low levels. Using this method, 13.5 ng of 3,3'4,4'-tetrachlorobiphenyl/g, 0.89 ng of 3,3'4,4',5-pentachlorobiphenyl/g and 0.64 ng of 3,3',4,4'5,5'-hexachlorobiphenyl/g were detected on wet weight basis in the blubber of a finless porpoise. To our knowledge this is the first report on the three toxic non-ortho chlorine substituted PCB residues detected in a higher mammal in the wilderness.     

Microwave Assisted Synthesis of 3,3',3″,3'″-o-,p-Phenylenedi-methylidinetetrakis-(4-hydroxy-2H-1-benzopyran-2-one)

Under microwave irradiation,2,2'-alkoxy-bridging or 4,4'-alkoxy-bridging dibenzaldehydes reacted with 4-hydroxycoumarin in DMF to give a series of 3,3',3″,3'″-o-and 3,3',3″,3'″-p-phenylenedimethylidinetetrakis-(4-hydroxy-2H-1-benzopyran-2-ones) in moderate yields.The structures of the synthetic coumarin derivatives were characterized with IR,1H NMR and MS spectroscopy as well as X-ray single crystallography.     

Reactivity-selectivity study of the Friedel-Crafts acetylation of 3,3' -dimethylbiphenyl and the oxidation of the acetyl derivatives

ABSTRACT: BACKGROUND: Friedel-Crafts acetylation is an important route to aromatic ketones, in research laboratories and in industry. The acetyl derivatives of 3,3' -dimethylbiphenyl (3,3' -dmbp) have applications in the field of liquid crystals and polymers and may be oxidized to the dicarboxylic acids and derivatives that are of interest in cancer treatment. FINDINGS: The effect of solvent and temperature on the selectivity of monoacetylation of 3,3'-dmbp by the Perrier addition procedure was studied using stoichiometric amounts of reagents. 4-Ac-3,3' -dmbp was formed almost quantitatively in boiling 1,2-dichloroethane and this is almost twice the yield hitherto reported. Using instead a molar ratio of substrate:AcCl:AlCl3 equal to 1:4:4 or 1:6:6 in boiling 1,2-dichloroethane, acetylation afforded 4,4' - and 4,6' -diacetyl-3,3' -dmbp in a total yield close to 100%. The acetyl derivatives were subsequently converted to the carboxylic acids by hypochlorite oxidation. The relative stabilities of the isomeric products and the corresponding sigma-complexes were studied by DFT calculations and the data indicated that mono- and diacetylation followed different mechanisms. CONCLUSIONS: Friedel-Crafts acetylation of 3,3' -dmbp using the Perrier addition procedure in boiling 1,2-dichloroethane was found to be superior to other recipes. The discrimination against the 6-acetyl derivative during monoacetylation seems to reflect a mechanism including an AcCl:AlCl3 complex or larger agglomerates as the electrophile, whereas the less selective diacetylations of the deactivated 4-Ac-3,3' -dmbp are suggested to include the acetyl cation as the electrophile. The DFT data also showed that complexation of intermediates and products with AlCl3 does not seem to be important in determining the mechanism.     

A rational synthesis of polyacrylates with discogenic side groups

The ferric chloride mediated oxidative coupling of 3,3 ,4,4-tetrahexyloxybiphenyl with 2-hexyloxyanisole followed by demethylation gave 3,6,7,10,11-pentahexyloxy-2-hydroxyor triphenylene. Reaction with tert -butyldimethylsilyl-protected 6-bromohexanol, removal of the protecting group, and condensation with acryloyl chloride methacryloyl chloride gave acrylate and methacrylate monomers with hexamethylene 'spacers'. Alternatively, reaction of 3,6,7,10,11-pentahexyloxy-2-hydroxytriphenylene with 2-(2-chloroethoxy)ethanol followed by acryloyl chloride or methacryloyl chloride gave acrylate and methacrylate monomers with diethylenoxy 'spacers'. Both of the poly(acrylate) homopolymers and the poly(methacrylate) homopolymer with the diethylenoxy 'spacer' gave columnar liquid crystal phases. This is contrary to the current perception that the methacrylate polymer backbone is too inflexible to be incorporated in columnar phases.     

Liquid crystalline model compounds based on 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA)

3,3',4,4'-Biphenyltetracarboxylic dianhydride (BPDA) was investigated as the central core unit in mesogenic molecules. Of particular interest was whether the BPDA unit could be self-constrained into a trans-conformation, and thus organize into a liquid crystalline phase. Two homologous series of symmetrical substituted model compounds, 3,3',4,4'-biphenyltetracarboxy-N-N'-bis-(4-n- alkylphenyl) diimides and 3,3',4,4'-biphenyltetracarboxy-N-N'-bis-(4-n- alkoxyphenyl)diimides were synthesized. For both series high temperature smectic A phases were observed. To our knowledge these are the first examples of liquid crystalline behaviour observed with BPDA as the mesogenic core.     

Viscosity and Structure of Melts of H Complexes of Acid Diesters of Aromatic Tetracarboxylic Acids with Aromatic Diamines

The viscosity, lifetime, and structure of melts of supramolecular H-bonded complexes of acid diethyl and dimethyl esters of 3,3',4,4'-(diphenyl oxide)tetracarboxylic or 3,3',4,4'-diphenyltetracarboxylic acids with aromatic diamines (diaminodiphenylmethane or m-phenylenediamine) are studied.     

Structure elucidation and NMR spectral assignments of three new lignan glycosides from Akebia trifoliata

Three new lignan glycosides (1-3) were isolated from the stems of Akebia trifoliata. Their structures were elucidated as (7R,8R,7'R,8'R)3,3',5,5'tetramethoxy-4,4'dihydroxy-7,9':7',9-diepoxylignan-4-O-beta-D-glucopyranoside (1), (7S,8S,8'R)-4,4',9-trihydroxy-3,3',5,5'-tetramethoxy-7,9'-epoxylignan-7'-one 9-O-beta-D-glucopyranoside (2), (7R,8R,8'S)-4,4',9-trihydroxy3,3',5,5'-tetramethoxy-7,9'-epoxylignan-7'-one 9-O-beta-D-glucopyranoside (3) by spectral analyses, primarily NMR, MS and CD. The NMR assignments for the compounds were carried out using 1H, 13C, DEPT, COSY, HSQC, HMBC and ROESY NMR experiments.     

Proton-Coupled Electron Transfer (PCET) with 1,4-Bisguanidino-Benzene Derivatives: Comparative Study and Use in Acid-Initiated C-H Activation

Proton-coupled electron transfer (PCET) is of key importance in modern synthetic chemistry. Redox-active guanidines were established by our group as valuable alternatives to toxic high-potential benzoquinones in a variety of different PCET reactions. In this work, the PCET reactivity of a series of 1,4-bisguanidino-benzenes varying in their redox potentials and proton affinities is evaluated. The relevant redox and protonation states are fully characterized, and the compounds sorted with respect to their PCET reactivity by comparative PCET experiments supplemented by quantum-chemical calculations. Depending on the studied reactions, the driving force is either electron transfer or proton transfer; thereby the influence of both processes on the overall reactivity could be assessed. Then, two of the PCET reagents are applied in representative oxidative aryl-aryl coupling reactions, namely the intramolecular coupling of 3,3’’-4,4’’-tetramethoxy-o-terphenyl to give the corresponding triphenylene, the intermolecular coupling of N-ethylcarbazole to give N,N’-diethyl-3,3’-bicarbazole, and in the oxidative lactonization of 2-[(4-methoxyphenyl)methyl]-benzoic acid. Under mild conditions, the reactions proceed fast and efficient. Only small amounts of acid are needed, in clear contrast to the corresponding coupling reactions with traditional high-potential benzoquinones such as DDQ or chloranil requiring a large excess of a strong acid.     

SYNTHESIS AND CHARACTERIZATION OF HIGHLY ORGANO-SOLUBLE POLYIMIDES BASED ON ALICYCLIC 1,8-DIMETHYL-BICYCLO[2.2.2]OCT-7- ENE-2,3,5,6-TETRACARBOXYLIC DIANHYDRIDE AND AROMATIC DIAMINES

Organo-soluble alicyclic polyimides (ALPIs) were synthesized from an alicyclic dianhydride, 1,8-dimethylbicyclo[2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (DMEA) and several multialkyl-substituted 4,4′-diaminodiphenylmethane compounds, including 3,3′-dimethyl-4,4′-diaminodiphenyl methane (DMDA), 3,3′,5,5′-tetramethyl-4,4′-diaminodiphenyl methane (TMDA) and 3,3′,5,5′-tetraethyl-4,4′-diaminodiphenylmethane (TEDA). For comparison, the aromatic polyimides (ARPIs) were synthesized from the aromatic dianhydride, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and the same diamines. The ALPIs exhibited better solubility and transparency,but worse thermal stabilities and mechanical properties than those of the ARPIs. And the ALPIs could be dissolved in common organic solvents, such as N-methyl-2-pyrrolidinone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), chloroform, tetrahydrofuran, m-cresol and so on. The ALPI films had an UV-Vis cut-off at 320 nm and a transmittance of higher than 80% in the visible region. In addition, the ALPIs showed thermal decomposition temperatures (Td) of about 450℃, which was nearly 100℃ lower than that of the ARPIs.     

Physicochemical study of spiropyran-terthiophene derivatives: photochemistry and thermodynamics

The photochemistry and thermodynamics of two terthiophene (TTh) derivatives bearing benzospiropyran (BSP) moieties, 1-(3,3″-dimethylindoline-6'-nitrobenzospiropyranyl)-2-ethyl 4,4″-didecyloxy-2,2':5',2″-terthiophene-3'-acetate (BSP-2) and 1-(3,3″-dimethylindoline-6'-nitrobenzospiropyranyl)-2-ethyl 4,4″-didecyloxy-2,2':5',2″-terthiophene-3'-carboxylate (BSP-3), differing only by a single methylene spacer unit, have been studied. The kinetics of photogeneration of the equivalent merocyanine (MC) isomers (MC-2 and MC-3, respectively), the isomerisation properties of MC-2 and MC-3, and the thermodynamic parameters have been studied in acetonitrile, and compared to the parent, non-TTh-functionalised, benzospiropyran derivative, BSP-1. Despite the close structural similarity of BSP-2 and BSP-3, their physicochemical properties were found to differ significantly; examples include activation energies (E(a(MC-2)) = 75.05 kJ mol(-1), E(a(MC-3)) = 100.39 kJ mol(-1)) and entropies of activation (ΔS = 43.38 J K(-1) mol(-1), ΔS = 37.78 J K(-1) mol(-1)) for the thermal relaxation from MC to BSP, with the MC-3 value much closer to the unmodified MC-1 value (46.48 J K(-1) mol(-1)) for this latter quantity. The thermal relaxation kinetics and solvatochromic behaviour of the derivatives in a range of solvents of differing polarity (ethanol, dichloromethane, acetone, toluene and diethyl ether) are also presented. Differences in the estimated values of these thermodynamic and kinetic parameters are discussed with reference to the molecular structure of the derivatives.     

The Crystal Structure of Biphenyltetracarboxylic Dianhydride Isomers

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Synthesis of bis(azafulvene)s by dehydration of hydroxymethylpyrrole derivatives

Bis(azafulvene) was isolated in 55% yield by the reaction of 4 equivalents of phenyllithium with 5,5'-diformyl-3,3',4,4'-tetraethyl-2,2'-bipyrrole followed by quenching with acetic anhydride. Unstable bis(azafulvene)s were obtained in much higher yields by dehydrating 5,5'-bis(hydroxymethyl) derivatives of 2,2'-bipyrrole and gem-dimethyl-2,2'-dipyrrylmethane with (Boc)2O-DMAP at room temperature. X-Ray crystallography of two bis(azafulvene)s is reported.     

A stereoselective synthesis of symmetrical and unsymmetrical bibenzo[e][1,3]oxazine-2,2′-dione derivatives induced by low-valent titanium reagent

A series of symmetrical and unsymmetrical bibenzo[e][1,3]oxazine-2,2′-dione derivatives were synthesized by the reaction of various o-hydroxy Schiff bases and triphosgene induced by low-valent titanium reagent (TiCl₄/Sm). A variety of substrates can participate in the process with good yields. The present method provides a useful preparation of 3,3′,4,4′-tetrahydro-4,4′-bibenzo[e][1,3]oxazine-2,2′-dione derivatives, which cannot be prepared otherwise. The mechanistic course of the reaction suggests the involvement of reduction, coupling, and cyclization by one-pot.     

Synthesis of nitrogen-bridged terthiophenes by tandem Buchwald-Hartwig coupling and their properties

The first synthesis of nitrogen-bridged terthiophenes (NBTTs) has been achieved by a tandem Buchwald-Hartwig coupling of 3,3',3",4'-tetrabromo-2,2':5',2"-terthiophene. Several NBTT derivatives bearing aryl or alkyl moieties on the N-atoms could be synthesized. Their fundamental electrochemical characteristics and HOMO-LUMO levels were found to be influenced by the substituents on the N-atoms.     

Novel hexasubstituted triphenylene discotic liquid crystals having three different types of peripheral substituent

The synthesis and mesomorphic properties of a variety of novel hexasubstituted triphenylene derivatives having three different types of peripheral substitutions are described. Monobromination of 2,3,6,7-tetrakis(pentyloxy)triphenylene 4, prepared by Suzuki coupling of 2-iodo-3′,4,4′,5-tetrakis(pentyloxy)biphenyl 2 and phenylboronic acid followed by cyclization, yields 10-bromo-2,3,6,7-tetrakis(pentyloxy)triphenylene 5. Nucleophilic aromatic displacement of the bromine with the potassium salt of pentanethiol, followed by bromination, yields 2-bromo-6,7,10,11-tetrakis(pentyloxy)-3-(pentylsulphanyl)triphenylene 7 having a bromo, thioalkyl and alkoxy-substituted periphery of the triphenylene nucleus. The reaction of 7 with copper(I) cyanide gives the cyanotriphenylene derivative 8, while palladium-copper catalysed alkynylation of 7 results in the synthesis of the substituted alkyne derivative 9. The deprotected alkyne 10 was converted to dimer 11 where two molecules of a monothioalkyl-tetra-alkoxytriphenylene are connected via a rigid π-conjugated diacetylene bridge. Compounds 7,8,9,10 form hexagonal columnar phases while the dimer 11 shows a discotic nematic phase.     

Six new metal-organic frameworks with multi-carboxylic acids and imidazole-based spacers: syntheses, structures and properties

Six new metal-organic frameworks [Cu(obba)(bimb)·(obbaH(2))](n) (1), [Cu(obba)(bimb)](n) (2), [Zn(2)(obba)(2)(bimb)(2)(DMF)(2)(H(2)O)(3.5)](n) (3), [Ni(3)(2,2',4,4'-bptcH)(2)(bimb)(2)(H(2)O)(2)·(H(2)O)(2)](n) (4), [Ni(2)(bimb)(3)(H(2)O)(6)·(aobtc)·(DMF)(2)·(H(2)O)(2)](n) (5) and [Cd(3,3',4,4'-bptcH(2))(H(2)O)·(bimb)](n) (6), were obtained by reactions of 4,4'-bis(1-imidazolyl)biphenyl (bimb) and multi-carboxylic acids of 4,4'-oxybis(benzoic acid) (obbaH(2)), 2,2',4,4'-biphenyltetracarboxylate acid (2,2',4,4'-bptcH(4)), azoxybenzene-3,3',5,5'-tetracarboxylic acid (aobtcH(4)), and 3,3',4,4'-biphenyltetracarboxylate acid (3,3',4,4'-bptcH(4)) with corresponding metal salts under hydro/solvothermal conditions, respectively. Complexes 1-3 have entangled structures with different topologies: 1 is a 3-fold interpenetrating NbO three-dimensional (3D) network; 2 is a 3-fold interpenetrating dmp 3D net; 3 is a 6-fold interpenetrating dia 3D chiral net containing rare 1D helical chains with the same handedness. Complex 4 is an uninodal 6-connected network with a Sch?fli symbol of (4(8)6(4)8(3)) based on the trinuclear Ni(II) subunits, while complexes 5 and 6 are 1D chains. Interestingly, compound 6 represents the rare example of MOFs that exhibit high photocatalytic activity for dye degradation under visible light and shows good stability towards photocatalysis. Complexes 3 and 6 exhibit intense blue emissions in the solid state at room temperature whereas 3 appears to be a good candidate of novel hybrid inorganic-organic NLO material.