Syntheses,Structure, Electrochemistry,and Optical Properties of 1,3‐Diethyl‐2,3‐dihydro‐1‐H‐1,3,2‐pyrido‐[4,5‐b]‐diazaboroles

Reaction of 2,5‐bis(dibromoboryl)thiophene ( 4 ) or 1,4‐bis(dibromoboryl)benzene ( 6 ) with two equivalents of N,N′‐dilithiated 2,3‐diaminopyridine ( 3 ) led to the generation of the pyridodiazaboroles 5 and 7 in which the two diazaborole rings are linked by 2,5‐thiophen‐diyl or 1,4‐phenylene units via the boron atom. The novel compounds were characterized by elemental analyses and spectroscopy (¹H‐, ¹¹B‐, ¹³C‐NMR, MS, and UV‐VIS). The molecular structure of 5 was elucidated by X‐ray diffraction. Cyclovoltammograms of 5 and 7 show two irreversible oxidation waves at 0.76 and 0.73 V, respectively vs Fc/Fc⁺. The novel compounds display intense blue luminescence with Stokes shifts of 76 and 74 nm and relative quantum yields of 39 and 43 % vs Coumarin 120 (Φ = 50 %).     

Hydrogen‐bonded thermotropic liquid‐crystalline polyester–amides from bis(hydroxy alkamido)aranes: Synthesis and properties

Hydrogen‐bonded aromatic–aliphatic polyester–amides (PEAs) were prepared by solution/melt polycondensation of aromatic–aliphatic amidodiols 1,4‐bis(4‐hydroxybutyramide)benzene (BHBB), 1,4‐bis(5‐hydroxy pentamide)benzene, 1,4‐bis(6‐hydroxyhexamide)benzene, 1,4‐bis(4‐hydroxybutyramidexylene), 1,4‐bis(5‐hydroxypentamidexylene, 1,4‐bis(4‐hydroxybutyramide)benzene, and 1,4‐bis(6‐hydroxyhexamidexylene) with terephthaloyl chloride/dimethyl terephthalate. Aromatic–aliphatic amido diols were prepared by the aminolysis of γ‐butyrolactone, δ‐valerolactone, and ?‐caprolactone with aromatic diamines such as paraphenylene diamine and paraxylene diamine. The monomers and polymers were characterized by chemical analysis (hydroxyl value and elemental analysis), Fourier transform infrared spectroscopy, ¹H NMR, and ¹³C NMR. The thermal‐ and phase‐transition behaviors of the polymers were investigated by differential scanning calorimetry in combination with hot‐stage optical microscopy. Crystallinity of polymers was examined with wide‐angle X‐ray diffraction. The polymers exhibited liquid crystallinity with layered structures formed by self‐organization of the hetero intermolecular hydrogen‐bonded networks indicating smectic phases except for PEAs prepared from BHBB. The hydrogen atom of the phenyl‐substituent group forces the neighboring carbonyl groups out of plane of the rings preventing formation of layered structures in the case of BHBB. The PEAs retained intermolecular hydrogen bonding even in the mesomorphic state, and variations in the hydrogen‐bonded lamellae/micelles might be responsible for the variations from one smectic to another texture. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 335–346, 2003     

Synthesis,crystal structure and photophysical properties of 1,4‐bis(1,3‐diazaazulen‐2‐yl)benzene: a new π building block

A dimerized 1,3‐diazaazulene derivative, namely 1,4‐bis(1,3‐diazaazulen‐2‐yl)benzene [or 2,2′‐(1,4‐phenylene)bis(1,3‐diazaazulene)], C₂₂H₁₄N₄, (I), has been synthesized successfully through the condensation reaction between 2‐methoxytropone and benzene‐1,4‐dicarboximidamide hydrochloride, and was characterized by ¹H NMR and ¹³C NMR spectroscopies, and ESI–MS. X‐ray diffraction analysis reveals that (I) has a nearly planar structure with good π‐electron delocalization, indicating that it might serve as a π building block. The crystal belongs to the monoclinic system. One‐dimensional chains were formed along the a axis through π–π interactions and adjacent chains are stabilized by C—H…N interactions, forming a three‐dimensional architecture. The solid emission of (I) in the crystalline form exhibited a 170 nm red shift compared with that in the solution state. The observed optical bandgap for (I) is 3.22 eV and a cyclic voltammetry experiment confirmed the energy levels of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). The calculated bandgap for (I) is 3.37 eV, which is very close to the experimental result. In addition, the polarizability and hyperpolarizability of (I) were appraised for its further application in second‐order nonlinear optical materials.     

Thermal analysis of 1,4‐di[n′‐(quinolyl)]buta‐1,3‐diynes,structure, and topo‐oligomerization: Polymerization of 3‐ethynylquinoline with the triethyl aluminum/vanadium 2,4‐pentanedionate catalyst system

Conjugated 1,4‐bis(n′‐quinolyl)‐1,3‐butadiynes were obtained through the oxidative dimerization of the corresponding n′‐ethynylquinolines catalyzed by cuprous chloride. Differential scanning calorimetry analysis of the 1,4‐bis[n′‐(quinolyl)]buta‐1,3‐diyne molecules produced evidence of a syn–anti rotational equilibrium around the 1,3‐diyne axis and an irreversible transformation into a thermopolymer. The topo‐oligomerization of 1,4‐bis[3′‐(quinolyl)]buta‐1,3‐diyne, which took place by irradiation with sunlight, was investigated with matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. Accurate X‐ray molecular structure and refinement analysis of 1,4‐bis[3′‐(quinolyl)]buta‐1,3‐diyne was conducted. The molecular crystalline packing consisted of parallel arrays of two groups of centrosymmetric molecules (antirotamer) in a herringbone assemblage in the solid state. The polymerization of 3‐ethynylquinoline was carried out with the AlEt₃/V(acac)₃ system to produce a mixture of 1,2,4‐ and 1,3,5‐tris(3′‐quinolyl)benzene cyclotrimers and a trans–cisoid polyene structure. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6031–6040, 2004     

Study of 1,3‐Dipolar Cycloaddition and Ring Contraction of New 1,4‐Phenylene‐bis[1,5]benzothiazepine Derivatives

Some 1,4‐phenylene‐bis[1,2,4]oxadiazolo‐[5,4‐d][1,5]benzothiazepine derivatives ( 4a , 4b , 4c ) were synthesized by 1,3‐dipolar cycloaddition reaction of benzohydroximinoyl chloride with 1,4‐phenylene‐bis(4‐aryl)‐2,3‐dihydro[1,5]benzothiazepine ( 2a , 2b , 2c ); meanwhile, compounds 2a , 2b , 2c also occurred ring contraction under acylating condition to obtain bis[2‐aryl‐2′‐(β‐1,4‐phenylenevinyl)‐3‐acetyl]‐2,3‐dihydro[1,5]benzothiazoles ( 3a , 3b , 3c ). The structures of some novel compounds were confirmed by IR, ¹H‐NMR, elemental, and X‐ray crystallographic analysis.     

Syntheses,Crystal Structures,and Magnetic Properties of Two Cobalt Coordination Polymers Constructed From 1,3‐Bis(2,4‐dicarboxyphenyl) Benzene and Bis(imidazole) Linkers

Abstract. The 3D cobalt(II) coordination polymers [Co_1.5(HDDB)(1,4‐bib)_1.5(H₂O)]_n ( 1 ), and {[Co₂(DDB)(1,3‐bib)₂(μ₂‐H₂O)] · H₂O}_n ( 2 ) were assembled by mixed‐ligand synthetic strategy [H₄DDB = 1,3‐bis(2,4‐dicarboxyphenyl) benzene, 1,3‐bib = 1,3‐bis(1H‐imidazol‐4‐yl)benzene, and 1,4‐bib = 1,4‐bis(1H‐imidazol‐4‐yl)benzene]. Their structures were determined by single‐crystal X‐ray diffraction analyses and further characterized by elemental analyses (EA), IR spectroscopy, powder X‐ray diffraction (PXRD), and thermogravimetric (TG) analyses. Single X‐ray diffraction analysis reveals that complex 1 is an interestingly 3D (3,3.6)‐connected (6³)₄(6⁵ · 8⁸ · 10²) net, and complex 2 is an unprecedented dinuclear [Co₂(COO)(μ₂‐H₂O)] SBUs based 3D (3,6)‐connected (3 · 6 · 7)(3² · 4³ · 5⁴ · 6³ · 7 · 8²) net. Additionally, the magnetic properties of 2 were investigated.     

A three‐dimensional cadmium coordination polymer based on 1,4‐bis(1,2,4‐triazol‐1‐yl)but‐2‐ene and benzene‐1,3,5‐tricarboxylic acid

The Cd^II three‐dimensional coordination poly[[[μ₄‐1,4‐bis(1,2,4‐triazol‐1‐yl)but‐2‐ene]bis(μ₃‐5‐carboxybenzene‐1,3‐dicarboxylato)dicadmium(II)] dihydrate], {[Cd₂(C₉H₄O₆)₂(C₈H₁₀N₆)]·2H₂O}_n , (I), has been synthesized by the hydrothermal reaction of Cd(NO₃)₂·4H₂O, benzene‐1,3,5‐tricarboxylic acid (1,3,5‐H₃BTC) and 1,4‐bis(1,2,4‐triazol‐1‐yl)but‐2‐ene (1,4‐btbe). The IR spectrum suggests the presence of protonated carboxylic acid, deprotonated carboxylate and triazolyl groups. The purity of the bulk sample was confirmed by elemental analysis and X‐ray powder diffraction. Single‐crystal X‐ray diffraction analysis reveals that the Cd^II ions adopt a five‐coordinated distorted trigonal–bipyramidal geometry, coordinated by three O atoms from three different 1,3,5‐HBTC²⁻ ligands and two N atoms from two different 1,4‐btbe ligands; the latter are situated on centres of inversion. The Cd^II centres are bridged by 1,3,5‐HBTC²⁻ and 1,4‐btbe ligands into an overall three‐dimensional framework. When the Cd^II centres and the tetradentate 1,4‐btbe ligands are regarded as nodes, the three‐dimensional topology can be simplified as a binodal 4,6‐connected network. Thermogravimetric analysis confirms the presence of lattice water in (I). Photoluminescence studies imply that the emission of (I) may be ascribed to intraligand fluorescence.     

Synthesis and properties of fluorinated polyimides from a new unsymmetrical diamine: 1,4‐(2′‐Trifluoromethyl‐4′,4′‐diaminodiphenoxy)benzene

A new aromatic, unsymmetrical ether diamine with a trifluoromethyl pendent group, 1,4‐(2′‐trifluoromethyl‐4′,4″‐diaminodiphenoxy)benzene, was successfully synthesized in three steps with hydroquinone as a starting material and polymerized with various aromatic tetracarboxylic acid dianhydrides, including 4,4′‐oxydiphthalic anhydride, 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride, 2,2′‐bis(3,4‐dicarboxyphenyl)‐hexafluoropropane dianhydride, and pyromellitic dianhydride, via a conventional two‐step thermal or chemical imidization method to produce a series of fluorinated polyimides. The polyimides were characterized with solubility tests, viscosity measurements, IR, ¹H NMR, and ¹³C NMR spectroscopy, X‐ray diffraction studies, and thermogravimetric analysis. The polyimides had inherent viscosities of 0.56–0.77 dL/g and were easily dissolved in both polar, aprotic solvents and common, low‐boiling‐point solvents. The resulting strong and flexible polyimide films exhibited excellent thermal stability, with decomposition temperatures (at 5% weight loss) above 522 °C and glass‐transition temperatures in the range of 232–272 °C. Moreover, the polymer films showed outstanding mechanical properties, with tensile strengths of 74.5–121.7 MPa, elongations at break of 6–13%, and initial moduli of 1.46–1.95 GPa, and good dielectric properties, with low dielectric constants of 1.82–2.53 at 10 MHz. Wide‐angle X‐ray diffraction measurements revealed that these polyimides were predominantly amorphous. These outstanding combined features ensure that the polymers are desirable candidate materials for advanced microelectronic applications. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6836–6846, 2006     

Three 2,5‐dialkoxy‐1,4‐diethynylbenzene derivatives

2,5‐Diethoxy‐1,4‐bis[(trimethylsilyl)ethynyl]benzene, C₂₀H₃₀O₂Si₂, (I), constitutes one of the first structurally characterized examples of a family of compounds, viz. the 2,5‐dialkoxy‐1,4‐bis[(trimethylsilyl)ethynyl]benzene derivatives, used in the preparation of oligo(phenyleneethynylene)s via Pd/Cu‐catalysed cross‐coupling. 2,5‐Diethoxy‐1,4‐diethynylbenzene, C₁₄H₁₄O₂, (II), results from protodesilylation of (I). 1,4‐Diethynyl‐2,5‐bis(heptyloxy)benzene, C₂₄H₃₄O₂, (III), is a long alkyloxy chain analogue of (II). The molecules of compounds (I)–(III) are located on sites with crystallographic inversion symmetry. The large substituents either in the alkynyl group or in the benzene ring have a marked effect on the packing and intermolecular interactions of adjacent molecules. All the compounds exhibit weak intermolecular interactions that are only slightly shorter than the sum of the van der Waals radii of the interacting atoms. Compound (I) displays C—H...π interactions between the methylene H atoms and the acetylenic C atom. Compound (II) shows π–π interactions between the acetylenic C atoms, complemented by C—H...π interactions between the methyl H atoms and the acetylenic C atoms. Unlike (I) or (II), compound (III) has weak nonclassical hydrogen‐bond‐type interactions between the acetylenic H atoms and the ether O atoms.     

A novel three‐dimensional zinc(II) coordination polymer based on 3,3′‐{[1,3‐phenylenebis(methylene)]bis(oxy)}dibenzoic acid and 1,4‐bis(pyridin‐4‐yl)benzene: synthesis,crystal structure and photocatalytic properties

A novel three‐dimensional (3D) Zn^II coordination polymer, namely, poly[[[1,4‐bis(pyridin‐4‐yl)benzene](μ₃‐3,3′‐{[1,3‐phenylenebis(methylene)]bis(oxy)}dibenzoato)zinc(II)] 1,4‐bis(pyridin‐4‐yl)benzene], {[Zn(C₂₂H₁₆O₆)(C₁₆H₁₂N₂)]·C₁₆H₁₂N₂}_n or {[Zn(PMBD)(DPB)]·DPB}_n, 1 , where H₂PMBD is 3,3′‐{[1,3‐phenylenebis(methylene)]bis(oxy)}dibenzoic acid and DPB is 1,4‐bis(pyridin‐4‐yl)benzene, has been synthesized by self‐assembly using zinc nitrate, a semi‐rigid dicarboxylic acid and a nitrogen‐containing ligand. The single‐crystal X‐ray structure determination indicates that 1 possesses an intriguing 3D architecture with a 4‐connected uninodal cds topology, which is constructed from dinuclear {Zn₂} clusters and V‐shaped PMBD^2? linkers. Compound 1 exhibits excellent photocatalytic activity on the degradation of the organic dyes Rhodamine B (RhB), Rhodamine 6G (Rh6G) and Methyl Red (MR).     

Syntheses,Crystal Structures,and Photocatalytic Activities of Three Copper Coordination Polymers Based on Bis(1H‐imidazol‐4‐yl)benzene/3‐(2‐Pyridyl)pyrazole

Three copper(II) coordination polymers (CuCPs), namely, [Cu_0.5(1,4‐bib)(SO₄)_0.5]_n ( 1 ), {[Cu(1,3‐bib)₂(H₂O)] · SO₄ · H₂O}_n ( 2 ), and [Cu(bpz)(SO₄)_0.5]_n ( 3 ), were assembled from the reaction of three N‐donors [1,4‐bib = 1,4‐bis(1H‐imidazol‐4‐yl)benzene, 1,3‐bib = 1,3‐bis(1H‐imidazol‐4‐yl)benzene, and Hbpz = 3‐(2‐pyridyl)pyrazole] with copper sulfate under hydrothermal conditions. Their structures were determined by single‐crystal X‐ray diffraction analyses and further characterized by elemental analyses (EA), IR spectroscopy, powder X‐ray diffraction (PXRD), and thermogravimetric analyses (TGA). Structure analyses reveal that complex 1 is a 3D 6‐connected {4¹² · 6³}‐ pcu net, complex 2 is a fourfold 3D 4‐connected 6⁶‐ dia net, whereas complex 3 is a 1D snake‐like chain, which further expanded into 3D supramolecular architectures with the help of C–H ··· O hydrogen bonds. Moreover, the photocatalytic tests demonstrate that the obtained CuCPs are photocatalysts in the degradation of MB with the efficiency is 86.4 % for 1 , 75.3 % for 2 , and 91.3 % for 3 after 2 h, respectively.     

Comparison of conventional and synchrotron X‐ray structure deter­minations of the adduct 1,2,4,5‐tetrahydroxybenzene–2,5‐dihydroxy‐1,4‐benzoquinone (1/1) and a conventional X‐ray structure determination of 1,2,4,5‐tetrahydroxybenzene monohydrate

The X‐ray structure of 1,2,4,5‐tetra­hydroxy­benzene (benzene‐1,2,4,5‐tetrol) monohydrate, C₆H₆O₄·H₂O, (I), reveals columns of 1,2,4,5‐tetra­hydroxy­benzene parallel to the b axis that are separated by 3.364 (12) and 3.453 (11) Å. Molecules in adjacent columns are tilted relative to each other by 27.78 (8)°. Water mol­ecules fill the channels between the columns and are involved in hydrogen‐bonding interactions with the 1,2,4,5‐tetra­hydroxy­benzene mol­ecules. The crystal structure of the adduct 1,2,4,5‐tetra­hydroxy­benzene–2,5‐di­hydroxy‐1,4‐benzo­quinone (1/1), C₆H₆O₄·C₆H₄O₄, (II), reveals alternating mol­ecules of 1,2,4,5‐tetra­hydroxy­benzene and 2,5‐di­hydroxy‐1,4‐benzo­quinone (both lying on inversion centers), and a zigzag hydrogen‐bonded network connecting mol­ecules in three dimensions. For compound (II), the conventional X‐ray determination, (IIa), is in very good agreement with the synchrotron X‐ray determination, (IIb). When differences in data collection temperatures are taken into account, even the displacement parameters are in very good agreement.     

Crystal Structure and Spectroscopic Characterization of Zinc(II) and Mercury(II) Complexes of N‐(Pyridin‐2‐ylmethylene)benzene‐1,4‐diamine

The behavior of N,N′‐bis(pyridin‐2‐ylmethylene)benzene‐1,4‐diamine (L) towards zinc(II), cadmium(II), and mercury(II) chlorides was studied in methanol solutions. In the presence of metal ions, the organic molecule was decomposed to N‐(pyridin‐2‐ylmethylene)benzene‐1,4‐diamine (L′), and complexes of general formula M(L′)Cl₂ were isolated from the mixture. The complexes were identified by elemental analysis, IR, ¹H NMR, and ¹³C NMR spectra, and their structures were further confirmed by single‐crystal X‐ray diffraction analysis of Zn(L′)Cl₂ and Hg(L′)Cl₂. In the solid state of both complexes, the molecules are stabilized by N–H ··· Cl hydrogen bonds and aromatic π–π stacking interactions.     

Report on an Unusual Cascade Reaction between Azulenes and 2,3‐Dichloro‐5,6‐dicyano‐1,4‐benzoquinone (=4,5‐Dichloro‐3,6‐dioxocyclohexa‐1,4‐diene‐1,2‐dicarbonitrile; DDQ)

The oxidation of 1‐(3,8‐dimethylazulen‐1‐yl)alkan‐1‐ones 1 with 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (=4,5‐dichloro‐3,6‐dioxocyclohexa‐1,4‐diene‐1,2‐dicarbonitrile; DDQ) in acetone/H₂O mixtures at room temperature does not only lead to the corresponding azulene‐1‐carboxaldehydes 2 but also, in small amounts, to three further products (Tables 1 and 2). The structures of the additional products 3 – 5 were solved spectroscopically, and that of 3a also by an X‐ray crystal‐structure analysis (Fig. 1). It is demonstrated that the bis(azulenylmethyl)‐substituted DDQ derivatives 5 yield on methanolysis or hydrolysis precursors, which in a cascade of reactions rearrange under loss of HCl into the pentacyclic compounds 3 (Schemes 4 and 7). The found 1,1′‐[carbonylbis(8‐methylazulene‐3,1‐diyl)]bis[ethanones] 4 are the result of further oxidation of the azulene‐1‐carboxaldehydes 2 to the corresponding azulene‐1‐carboxylic acids (Schemes 9 and 10).     

A new two‐dimensional ZnII coordination polymer based on 1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene and 5‐nitrobenzene‐1,3‐dicarboxylic acid: synthesis,crystal structure and physical properties

A novel two‐dimensional (2D) Zn^II coordination framework, poly[[μ‐1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene](μ‐5‐nitrobenzene‐1,3‐dicarboxylato)zinc(II)], [Zn(C₈H₃NO₆)(C₁₄H₁₄N₄)]_n or [Zn(NO₂‐BDC)(1,3‐BMIB)]_n [1,3‐BMIB is 1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene and NO₂‐H₂BDC is 5‐nitrobenzene‐1,3‐dicarboxylic acid], has been prepared and characterized by IR, elemental analysis, thermal analysis and single‐crystal X‐ray diffraction. Single‐crystal X‐ray diffraction analysis revealed that the compound is a new 2D polymer with a 6³ topology parallel to the (10) crystal planes based on left‐handed helices, right‐handed helical NO₂‐BDC–Zn chains and [Zn₂(1,3‐BMIB)₂]_n clusters. In the crystal, adjacent layers are further connected by C—H…O hydrogen bonds, C—H…π interactions, C—O…π interactions and N—O…π interactions to form a three‐dimensional structure in the solid state. In addition, the compound exhibits strong fluorescence emissions in the solid state at room temperature.     

A three‐dimensional ZnII coordination polymer constructed from 1,1′‐biphenyl‐2,2′,4,4′‐tetracarboxylate and 1,4‐bis(1H‐imidazol‐1‐yl)benzene ligands exhibiting photoluminescence

Ligands based on polycarboxylic acids are excellent building blocks for the construction of coordination polymers; they may bind to a variety of metal ions and form clusters, as well as extended chain or network structures. Among these building blocks, biphenyltetracarboxylic acids (H₄bpta) with C ₂ symmetry have recently attracted attention because of their variable bridging and multidentate chelating modes. The new luminescent three‐dimensional coordination polymer poly[(μ₅‐1,1′‐biphenyl‐2,2′,4,4′‐tetracarboxylato)bis[μ₂‐1,4‐bis(1H‐imidazol‐1‐yl)benzene]dizinc(II)], [Zn₂(C₁₆H₆O₈)(C₁₂H₁₀N₄)]_n , was synthesized solvothermally and characterized by single‐crystal X‐ray diffraction, elemental analysis and IR spectroscopy. The crystal structure contains two crystallographically independent Zn^II cations. Both metal cations are located on twofold axes and display distorted tetrahedral coordination geometries. Neighbouring Zn^II centres are bridged by carboxylate groups in the syn –anti mode to form one‐dimensional chains. Adjacent chains are linked through 1,1′‐biphenyl‐2,2′,4,4′‐tetracarboxylate and 1,4‐bis(1H‐imidazol‐1‐yl)benzene ligands to form a three‐dimensional network. In the solid state, the compound exhibits blue photoluminescence and represents a promising candidate for a thermally stable and solvent‐resistant blue fluorescent material.     

立体选择性合成2-(a-噻吩甲酰基)-3-取代苯基-4-乙氧羰基-5-甲基-反式-2,3-二氢呋喃

溴化(a-噻吩甲酰基)甲基三苯鉮1与3-取代苯甲叉基-2,4-戊二酮 2以碳酸钾为碱,在苯中55℃条件下反应,可以较好的收率、高立体选择性地生成反-2-(a-噻吩甲酰基)-3-取代苯基-4-乙氧羰基-5-甲基-2,3-二氢呋喃3。产物结构均经波谱予以确定。本文还提出了生成产物的可能机理。     

Eco‐friendly HClO4–SiO2 catalyzed synthesis of mono‐ and bis‐diaryl‐2h‐1,4 benzothiazines

Mono‐ and bis‐diaryl‐2H‐1,4‐benzothiazines were obtained in quantitative yields through silica‐supported perchloric acid catalyzed reaction cascade of double condensation and 1,4 addition of diaroylacetylenes with 2‐aminothiophenol at room temperature. The structures were confirmed by spectroscopic analyses and X‐ray crystallographic studies. J. Heterocyclic Chem., (2011)     

N‐(2‐Hydroxyethyl)‐N‐methyldithiocarbamato Complexes of Nickel(II) with Phosphorus Donor Ligands

Planar nickel(II) complexes involving N‐(2‐Hydroxyethyl)‐N‐methyldithiocarbamate, such as [NiX(nmedtc)(PPh₃)] (X = Cl, NCS; PPh₃ = triphenylphosphine), and [Ni(nmedtc)(P‐P)]ClO₄(P‐P = 1,1‐bis(diphenylphosphino)methane(dppm); 1,3‐bis(diphenylphosphino)propane (1,3‐dppp); 1,4‐bis(diphenylphosphino)butane(1,4‐dppb) have been synthesized. The complexes have been characterized by elemental analyses, IR and electronic spectroscopies. The increased νC–N value in all the complexes is due to the mesomeric drift of electrons from the dithiocarbamate ligands to the metal atom. Single crystal X‐ray structure of [Ni(nmedtc)(1,3‐dppp)]ClO₄·H₂O is reported. In the present 1,3‐dppp chelate, the P–Ni–P angle is higher than that found in 1,2‐bis(diphenylphosphino)ethane‐nickel chelates and lower than 1,4‐bis(diphenylphosphino)butane‐nickel chelates, as a result of presence of the flexible propyl back bone connecting the two phosphorus atoms of the complex.     

Synthesis of Tetraoxygenated Terephthalates via a Dichloroquinone Route: Characterization of Cross‐Conjugated Liebermann Betaine Intermediates

Cross‐conjugated quinoid betaines 4 (2,5‐bis(alkoxycarbonyl)‐3,6‐dioxo‐4‐(1‐pyridinium‐1‐yl)cyclohexa‐1,4‐dien‐1‐olates; Liebermann betaines) were synthesized from 2,5‐dichloro‐3,6‐dioxocyclohexa‐1,4‐diene‐1,4‐dicarboxylates ( 2 ) and pyridines in acetone containing H₂O. Their structure was secured by NMR spectroscopy and by X‐ray diffraction analysis of 4f (alkoxy = EtO, pyridine = 4‐Me₂N–C₅H₄N). Betaines 4 show comparatively high reactivity towards nucleophiles as a consequence of their cross‐conjugated character. Betaine 4a and hydroxy‐3,4‐methylenedioxybenzene (sesamol) condense to give a pyridinium quinolate salt 14 which has a bifurcate H‐bond from a pyridinium N⁺–H donor to both carbonyl (C=O) and olate (C–O⁻) acceptors in the solid state. Betaine 4b hydrolyzes in aqueous solution to give diethyl 2,5‐dihydroxy‐3,6‐dioxocyclohexa‐1,4‐diene‐1,4‐dicarboxylate ( 11 ) as a pyridinium salt, or as polymeric zinc(II) complex of the dianion of 11 in the presence of ZnCl₂. Dihydroxyquinone 11 was analytically differentiated from its independently prepared hydroquinone form, diethyl 2,3,5,6‐tetrahydroxyterephthalate ( 12 ), by NMR analysis in solution and X‐ray crystal structure determination of both compounds.