Two highly connected POM-based hybrids varying from 2D to 3D: The use of the isomeric ligands

Through employing two isomeric ligands, isonicotinic acid (HINA) and nicotinic acid (HNA), with different electron delocalization nature, two high-dimensional hybrids based on highly connected α-metatungstate clusters, [Na₂(H₂O)₈Ag₂(HINA)₃(INA)][Na(H₂O)₂Ag₂(HINA)₄(H₂W₁₂O₄₀)]·2H₂O (1) and [Na₂(H₂O)₄Ag₆(HNA)₂(NA)₂(H₂W₁₂O₄₀)]·8H₂O (2), have been conventionally synthesized and structurally characterized. 1 exhibits an unusual 1D-in-2D pseudo-polyrotaxane entangled structure, namely, the 2D sheets [Na(H₂O)₂Ag₂(HINA)₄(H₂W₁₂O₄₀)]_n³ⁿ⁻ are penetrated by enantiomorphous meso-helical chains [Na₂(H₂O)₈Ag₂(HINA)₃(INA)]_n³ⁿ⁺. In the 2D sheets, each [H₂W₁₂O₄₀]⁶⁻ cluster is surrounded by six Ag and two Na atoms. 2 exhibits a 3D (4, 6)-net structure with (3²6²7²)(3²4⁴5⁴6⁴7)(3²4⁴6⁸7) topology, in which each [H₂W₁₂O₄₀]⁶⁻ cluster is connected with ten Ag atoms. These facts indicate that the isomeric ligands play a key role in the formation of final structures. From 1 to 2, the connection number of the [H₂W₁₂O₄₀]⁶⁻ cluster changes from 8 to 10 and the dimensionality increases from 2 to 3. Moreover, 1 and 2 display photoluminescent properties in the blue range at room temperature.     

Ruthenium-catalyzed annulation of aromatic ketones with internal alkynes: A reliable route to substituted naphthalene derivatives

We report herein the preparation of polysubstituted naphthalene derivatives by the ruthenium-catalyzed benzannulation reaction of aromatic ketones with internal alkynes. This method (1) forms two new carbon-carbon bonds in one single step, (2) accommodates a variety of functional groups, and (3) undergoes mild reaction conditions.     

Vibronic pairwise charge transfer in copper-oxide sheets: A possible approach to high temperature superconductivity theory

Summary To accommodate the number of holes and fractional number of atoms in doped highT _c superconductors, and to produce a periodic structure with given symmetry, we postulate a quadruple cell with four copper atoms on the CuO₂ layer. The quadruple cell structure hasD _2h symmetry which can be distorted toC _2h geometry underB _1g vibration. Such a structure allows the interconversion of different spin angular momenta into paired spins similar to Cooper pairs. It also provides vibronic interactions that lower the energy of the ground state. For electron (hole) pairing, we construct the running wave Bloch sums consisting of linear combination of bonding/antibonding geminals (instead of one-electron atomic orbitals) in these quadruple cells. For bond movement we construct the Bloch sums consisting of linear combination of Covalon waves in quadruple cells related to the movement of conjugate (alternating) bonds. In both cases the pair-wise charge (hole/electron) transfer is coupled with antisymmetric vibrations under a double-well potential related to Peierls distortion. The vibronic mixing of different running bonds with different antisymmetric vibrations at various distances, accounts for the different long-range order of charge transfer. Our formulations represent an alternative view of BCS theory, Bisoliton theory and Resonanting Valence Bond theory by using a quantum chemical, position-space approach to a more tight binding situation.     

Indium oxide co-doped with tin and zinc: A simple route to highly conducting high density targets for TCO thin-film fabrication

Indium oxide co-doped with tin and zinc (ITZO) ceramics have been successfully prepared by direct sintering of the powders mixture at 1300 °C. This allowed us to easily fabricate large highly dense target suitable for sputtering transparent conducting oxide (TCO) films, without using any cold or hot pressing techniques. Hence, the optimized ITZO ceramic reaches a high relative bulk density (∼ 92% of In₂O₃ theoretical density) and higher than the well-known indium oxide doped with tin (ITO) prepared under similar conditions. All X-ray diagrams obtained for ITZO ceramics confirms a bixbyte structure typical for In₂O₃ only. This indicates a higher solubility limit of Sn and Zn when they are co-doped into In₂O₃ forming a solid-solution. A very low value of electrical resistivity is obtained for [In₂O₃:Sn_0.10]:Zn_0.10 (1.7 × 10⁻³ Ω cm, lower than ITO counterpart) which could be fabricated to high dense ceramic target suing pressure-less sintering.     

Reactivity of substituted 1,2-dithiole-3-thiones with sodium ethanethiolate: a convenient route to a novel heterocycle

Sodium ethanethiolate reacts at the S-2 position of substituted 1,2-dithiole-3-thiones to give various products depending on the substiuents at the C-4 and C-5 positions. In particular, the presence of a pyrimidinyl substituent induces some noticeable changes in the reaction pathway, yielding a novel heterocycle whose synthesis has not been previously reported.     

A [3+2] dipolar cycloaddition route to 3-hydroxy-3-alkyl oxindoles: an approach to pyrrolidinoindoline alkaloids

A [3 + 2] cycloaddition approach to the 3-hydroxy-3-alkyl oxindole scaffold is described. Isoxazolines obtained by cycloaddition of nitrile oxide 3 with 3-methylene oxindoles were elaborated to 3-hydroxy-3-cyanomethyl oxindoles employing a one-pot protocol en route to the pyrrolidinoindoline moiety which is found in many natural products. The total syntheses of alkaloids (±)-alline and (±)-CPC-1 were achieved using this methodology.     

The acid catalysed reaction of 1,4-diketones with hydrogen sulphide : A convenient route to substituted thiophens

Various 1,4-diketones and 2-ethoxycarbonyl-1,4-diketones have been reacted with H₂S in acidic ethanol to give 2,5- or higher substituted thiophens as resulting from a spontaneous ring-closure reaction of initially formed sulphur analogues of the starting diketones. In some the corresponding 2-mercapto-2,3-dihydrothiophens and/or 2,5-dimercaptotetrahydrothiophens were formed as by-products. 1,4-Diphenyl-1,4-diketones behaved exceptionally under similar reaction conditions yielding preferentially 2,5-diphenylfurans.     

A concise and efficient route to 2alpha-(omega-hydroxyalkoxy)-1alpha,25-dihydroxyvi tam in D3: remarkably high affinity to vitamin D receptor

[reaction: see text]A convenient and potentially valuable synthetic approach to the novel 2alpha-functionalized 1alpha,25-dihydroxyvitamin D3 [1alpha,25(OH)2D3] derivatives (1a-c), which are the C2-epimer of ED-71 and its analogues, has been developed. The C2alpha-modified ring A precursors (1,7-enynes 16, n = 0, 1, and 2) were constructed stereoselectively starting from D-glucose in high yield. In the synthesized 2alpha-(omega-hydroxyalkoxy)-1alpha,25(OH)2D3 derivatives, 1a and 1b showed a greater binding affinity to vitamin D receptor (VDR), up to 1.8 times that of the native hormone.     

Synthesis of alpha-amino-alpha'-diazomethyl ketones via ring opening of substituted cyclopropanones with alkyl azides. A facile route to N-substituted 3-azetidinones

[reaction: see text] The reaction of alkyl azides with triethyl(1-methoxy-2, 2-dimethyl-cyclopropoxy)silane affords a series of alpha-amino-alpha'-diazomethyl ketones in moderate yields (38-54%). The mechanism of this novel process is discussed. The diazomethyl ketones could also be cyclized to the corresponding N-substituted 3-azetidinones in good yield upon treatment with Rh(2)(OAc)(4).     

Reactions of N-hydroxysuccinimide esters of anthranilic acids with anions of beta-keto esters. A new route to 4-oxo-3-quinolinecarboxylic acid derivatives

A new approach for the synthesis of 4-oxo-3-quinolinecarboxylic acid derivatives is described. This methodology involves the C-acylation of the anions of appropriate beta-keto esters with novel N-hydroxysuccinimide esters of anthranilic acids. The intermediate C-acylation products 3 are spontaneously cyclized to afford 3-ethoxycarbonyl-4-oxoquinoline derivatives 4. The introduction of a variety of substituents at positions 1 and 2 of the quinoline ring is feasible with the selection of suitable anthranilic acids and beta-keto esters. The structure of the obtained 2-substituted 3-ethoxycarbonyl-4-oxoquinolines was confirmed by IR and NMR spectral data.     

Photoredox-catalyzed sulfenylation/cyclization of N-aryl-N-tosylpropargylamine with disulfide: A concise route to 3-phenylthioquinoline

A facile and novel protocol for one-pot synthesis of 3-phenylthioquinoline derivates via visible-light induced tandem cyclization of N-aryl-N-tosylpropargylamine with disulfides was developed. This unprecedented method, involving CS bond formation, detosylation and aromatization, afforded the desired products in a broad substrate scope under mild conditions.     

Palladium-catalyzed borylation of aryl halides or triflates with dialkoxyborane: A novel and facile synthetic route to arylboronates

A direct borylation of aryl halides or triflates with dialkoxyborane was investigated. The coupling reaction of pinacolborane with aryl halides or triflates in the presence of a catalytic amount of PdCl(2)(dppf) together with a base provided arylboronates in high yields. The product distributions were strongly dependent on the base employed, and the tertiary amine, especially Et(3)N, was effective for the selective formation of the boron-carbon bond. The reaction conditions were so mild that arylboronates having a variety of functional groups such as carbonyl, cyano, and nitro groups were readily prepared.     

Studies with azoles and benzoazoles: A novel simple approach for synthesis of 3‐functionally substituted 3‐acylindoles

3‐Substituted acylindoles 8 are obtained via refluxing carboxylic acids with indole in acetic anhydride solutions. The formed 3‐substituted acylindole 8a is readily converted into 4‐aminopyrazol‐3‐ylindoles 20 , and into 22 . Indole reacts with chloroacetyl chloride to yield: 3‐chloroacetylindole 9 which could also be utilized for synthesis of a number of 3‐substituted indoles.     

The reaction of enamines with β-ketoesters: A route to γ-pyrones

β-Ketoesters and enamines are found to react at elevated temperatures to give γ-pyrones in yields of 10 to 50%.     

Vitamin D and click chemistry. Part 1: A stereoselective route to vitamin D analogues with triazole rings in their side chains

Efficient preparation of vitamin D CD ring system synthons with triazole rings in their side chains is based on the formation of the triazole ring from a [3+2]-cycloaddition of a vitamin D side chain terminal azide with a terminal acetylene.     

Thieno[3,2‐b]thiophene‐substituted benzodithiophene in donor–acceptor type semiconducting copolymers: A feasible approach to improve performances of organic photovoltaic cells

Thieno[3,2‐b]thiophene‐substituted benzo[1,2‐b:4,5‐b′]dithiophene donor units (TTBDT) serve as novel promising building blocks for donor–acceptor (D‐A) copolymers in organic photovoltaic cells. In this study, a new D‐A type copolymer (PTTBDT‐TPD) consisting of TTBDT and thieno[3,4‐c]pyrrole‐4,6‐dione (TPD) is synthesized by Stille coupling polymerization. A PTTBDT‐TPD analog consisting of TTBDT and alkylthienyl‐substituted BDT (PTBDT‐TPD) is also synthesized to compare the optical, electrochemical, morphological, and photovoltaic properties of the polymers. Bulk heterojunction photovoltaic devices are fabricated using the polymers as p‐type donors and [6,6]‐phenyl C₇₁‐butyric acid methyl ester (PC₇₁BM) as the n‐type acceptor. The power conversion efficiencies of the devices fabricated using PTTBDT‐TPD and PTBDT‐TPD are 6.03 and 5.44%, respectively. The difference in efficiency is attributed to the broad UV–visible absorption and high crystallinity of PTTBDT‐TPD. The replacement of the alkylthienyl moiety with thieno[3,2‐b]thiophene on BDT can yield broad UV–visible absorption due to extended π‐conjugation, and enhanced molecular ordering and orientation for organic photovoltaic cells. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3608–3616     

A synthetic route to highly substituted 1,2,3,4-tetrahydroisoquinolines via Yb(OTf)3 -catalyzed diastereoselective ring opening of bridged oxazolidines: asymmetric synthesis of 2-azapodophyllotoxin

We herein report a robust and efficient synthetic route to highly functionalized enantiopure 1,2,3,4-tetrahydroisoquinolines (THIQs) from Garner aldehyde. We utilized the inherent chirality of Garner aldehyde through 1,2- and 1,3-/1,4-asymmetric inductions iteratively to obtain 1,2,3,4-tetrasubstitued THIQs using rigid and isolable bridged oxazolidines without any external chiral sources. All possible stereoisomers of bridged oxazoliodines were efficiently synthesized from L- and D-Garner aldehydes and transformed into fully functionalized THIQs via diastereoselective ring opening with various nucleophiles in the presence of Yb(OTf)(3). This methodology furnished four out of eight possible diastereomers of 1,2,3,4-tetrasubstituted THIQs despite the electronic nature of substituents on the aryl rings. Finally, the enantioselective synthesis of 2-azapodophyllotoxin was achieved with an overall yield of 35.4% (eight steps) from D-Garner aldehyde using this synthetic route.     

Deoxydative thiation of 3-substituted pyridine N-oxides with 4-methoxytoluene-α-thiol: A divergent route to pyridinethiols

Synthesis of 3-substituted 2-pyridinethiols was achieved by thiation of pyridine N-oxides with 4-methoxytoluene-α-thiol in the presence of diethylcarbamoyl chloride followed by cleavage of the resulting sulfides. The ease of substitution was shown to be affected by nucleophilicity of the N-oxide oxygen. Addition of zinc bromide to the reaction, a need for triethylamine, decreased most of the yield for thiation products but the formation of 3-methoxy-2-methoxybenzylthiopyridine was only improved. A plausible mechanism of the substitution, particularly β-thiation to the N-oxide function, is discussed compared with the regiochemistry observed in the reaction with diethoxyphosphoryl chloride instead of diethylcarbamoyl chloride. The debenzylation to pyridinethiol was also found to be dependent on the electron-density in the pyridine ring.