Palladium-Catalyzed Coupling of Ethynylated p-Carborane Derivatives: Synthesis and Structural Characterization of Modular Ethynylated p-Carborane Molecules

Methodology leading to a new class of rodlike p-carborane derivatives is described, involving the palladium-catalyzed coupling of B-iodinated p-carboranes with terminal alkynes. The products of these reactions contain an alkyne substituent at a boron vertex of the p-carborane cage. Reaction of closo-2-I-1,12-C(2)B(10)H(11) (1) with closo-2-(C&tbd1;CH)-1,12-C(2)B(10)H(11) (3) in the presence of pyrrolidine and catalytic quantities of bis(triphenylphosphine)palladium dichloride and cupric iodide yields 1,2-(closo-1',12'-C(2)B(10)H(11)-2'-yl)(2) acetylene (4). Oxidative coupling of 3 in the presence of cupric chloride in piperidine affords 1,4-(closo-1',12'-C(2)B(10)H(11)-2'-yl)(2)-1,3-butadiyne (5). Reaction of 2 molar equiv. of closo-2,9-I(2)-1,12-C(2)B(10)H(10) (6) withcloso-2,9-(C&tbd1;CH)(2)-1,12-C(2)B(10)H(10) (7) in the presence of pyrrolidine and catalytic quantities of bis(triphenylphosphine)palladium dichloride and cupric iodide yields closo-2,9-(closo-2'-I-9'-C&tbd1;C-1',12'-C(2)B(10)H(10))(2)-1,12-C(2)B(10)H(10) (8), a rigid, iodine-terminated carborod trimer in which the p-carborane cages are linked at the 2 and 9 B-vertices by alkyne (C&tbd1;C) bridges. The molecular structures of 5 and the previously described closo-2,9-(C&tbd1;CSiMe(3))(2)-1,12-C(2)B(10)H(10) (9) have been determined by X-ray crystallography. Crystallographic data are as follows: for 5, monoclinic, space group P2/a, a = 12.352(6) ?, b = 14.169 (6) ?, c = 12.384(5) ?, beta = 109.69(2) degrees, V = 2041 ?(3), Z = 4, R = 0.098, R(w)( )()= 0.135; for 9, monoclinic, space group C2/m, a = 22.111(4) ?, b = 7.565(2) ?, c = 6.943(2) ?, beta = 107.871(8) degrees, V = 1105 ?(3), Z = 2, R = 0.059, R(w)( )()= 0.090.     

Synthesis and thermal properties of azo-peroxyesters

Abstract  

New azo-perester derivatives of tert-butyl and tert-amyl hydroperoxides were obtained in reactions of azo acid chlorides with hydroperoxides in the presence of an inorganic base. Obtained azo-peresters possess two kinds of the labile functional groups: the azo group and also the perester group. The data from DSC experiments indicate that in the case of azo-perester derivatives of tert-amyl hydroperoxide, the perester group decomposes at a somewhat lower temperature than in the case of tert-butyl derivatives, whereas azo groups decompose at somewhat higher temperature in the case of derivatives with tert-amyl substituent.     

Synthesis and thermal properties of azo-peroxyesters

Abstract  New azo-perester derivatives of tert-butyl and tert-amyl hydroperoxides were obtained in reactions of azo acid chlorides with hydroperoxides in the presence of an inorganic base. Obtained azo-peresters possess two kinds of the labile functional groups: the azo group and also the perester group. The data from DSC experiments indicate that in the case of azo-perester derivatives of tert-amyl hydroperoxide, the perester group decomposes at a somewhat lower temperature than in the case of tert-butyl derivatives, whereas azo groups decompose at somewhat higher temperature in the case of derivatives with tert-amyl substituent. Graphical abstract        

Nanocrystalline calcium peroxide: Synthesis,thermal and chemosorption properties

Nanocrystalline СаО₂ was synthesized using microwave technology. Vacuum and microwave drying was shown to yield nanosized calcium peroxide without organic dispersants. The size of synthesized particles was shown to have an effect on the thermal and CO₂ chemosorption properties of calcium peroxide.     

Synthesis and thermal properties of cellulose-based polycaprolactones

Cellulose-based polycaprolactone (CAPCL) sheets were prepared from cellulose acetate (CA) and ϵ-caprolactone (CL). Thermal properties of the obtained CAPCL's were studied by differential scanning calorimetry (DSC), thermogravimetry (TG) and TG-Fourier transform infrared spectrometry (TG-FTIR). The glass transition temperatures (T_g 's) of CAPCL decreased with increasing CL/OH ratio, until CL/OH ratio reached 15 and then increased above that ratio. Melting of CAPCL was observed when CL/OH ratio was over 10. The thermal degradation temperatures (T_d 's) of CAPCL increased from ca. 350 °C to 390 °C with increasing CL/OH ratio. The results obtained by TG-FTIR analysis of CAPCL showed that gases with OH, CH, C=O, C-O-C groups evolved by thermal degradation.     

Synthesis and thermal properties of asymmetrical azo-peresters

Abstract  

New asymmetrical azo-perester derivatives of tert-butyl and tert-amyl hydroperoxides were obtained by reacting azo acids with hydroperoxides in the presence of N,N′-carbonyldiimidazole. The obtained azo-peresters possess two labile functional groups: the azo group and the perester group. Data from dynamic differential scanning calorimetry (DSC) experiments indicate that the azo groups decompose at somewhat lower temperatures than the perester groups.     

The POSS side chain epoxy nanocomposite: Synthesis and thermal properties

The IPI‐POSS‐modified epoxy resin (IPEP) was prepared from isocyanato‐propyldinethylsilyl‐isobutyl‐POSS (IPI‐POSS) and diglycidyl ether of bisphenol A epoxy resin. The steric hindrance of the IPEP bulky POSS side chain improved the curing activation energies. The POSS particles sizes were about 2–3 nm and dispersed uniformly. At lower IPEP concentration (POSS < 12 wt %), the glass transition temperatures (T_gs) of the IPEP nanocomposites increased from 118 to 170 °C. The char yield increased from 15 to 20 wt %, and the LOI values increased from 22 to 28. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 643–652, 2010     

Synthesis and thermal properties of aryl-substituted rod-like polyimides

This article describes the synthesis and thermal characterization of novel aryl-substituted rod-like homopolyimides. Synthetic aspects of monomer syntheses and one-step polymer synthesis in m-cresol are presented. Polyimides with rod-like chain structure are based on monophenylated pyromellitic dianhydride (MPPMDA), diphenylated pyromellitic dianhydride (DPPMDA), and as rod-like diamine units on phenylated para-phenylene diamine and 1,1′-binaphthyl-4,4′-diamine. As partial flexible units, which have the possibility to be converted into an extended chain conformation, commercially available 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 3,4′-oxydianiline (3,4′-ODA) were used. The polyimides were investigated with respect to solution properties and thermal behavior. © 1993 John Wiley & Sons, Inc.     

Synthesis and thermal properties of crosslinkable phosphazene copolymers

Polyphosphazenes of formula [NP(OC₆H₄CN)_x(OCH₂CF₃)_2?x] (x = 0.04–2) were prepared. The copolymers were crosslinked via cyclotrimerization of the nitrilic function, using acid catalysts (chlorosulfonic acid, aluminum chloride) at elevated temperatures. The thermal properties of the crosslinked cyclomatrix polymer were compared to the linear polymer by thermogravimetric analysis and differential scanning calorimetry. When the 4-cyanophenoxy-2,2,2-trifluoroethoxy ratios were less than 0.2, the crosslinked polymers were soluble in polar organic solvents.     

Synthesis and thermal properties of dimeric alkoxy-substituted tolans

Four homologous series of dimeric tolans of the general formula RC₆H₄C≏C₆H₄O(CH₂)_m OC₆H₄C'CC₆H₄R (m'6-10; R'H, OC₆H₁₃, OC₁₀H₂₁ and OC₁₄H₂₉), denoted further as TOmOT or nOTOmOTOn, according to the number of aliphatic carbon atoms, have been synthesized. Dimers with terminal chains exhibited liquid crystalline behaviour. Crystal-crystal transitions were also observed. Resulting from the optical, thermal and miscibility studies, the following mesophases have been identified: nematic, smectics A and B, and the tilted smectics C and (probably) F or I. In the 6OTOmOTO6 series, a phase with a strong tendency to self-alignment occurred between the nematic and smectic A phases. This phase resembled the nematic in its viscoelastic properties, but also showed focal-conic textures. A transition between this 'intermediate phase' and the nematic was detected only from microscopic observations. On the contrary, the 'intermediate phase'-smectic A transition was also detected by DSC (δH ∼ 1kJ mol^-1). Both tilted (S_c and S_F/I) and non-tilted (S_A and S_B) smectics were observed in the 10OTOmOTO10 series, while only tilted smectic phases were identified in the dimers with longer terminal substituents (14OTOmOTO14). Double melting behaviour was found in 14OTO8OTO14 and 14OTO10OTO14. An alternation of the transition temperatures and enthalpies with the odd-even alternation of the lengths of bridging groups was clearly observed. A correlation between total enthalpies of transition and solubilities of the dimeric tolans is stated.     

Synthesis and thermal properties of spiro phosphorus compounds

Intumescent materials, 3,9-dichloro-2,4,8,10-tetraoxa-3,9-diphosphaspiro-[5,5]-undecane-3,9-dioxide and 3,9-dichloro-2,4,8,10-tetraoxa-3,9-diphosphaspiro-[5,5]-undecane having the capacity to produce dehydrating agent, blowing agent, and undergo carbonization during burning have been synthesized. The thermal behavior of the synthesized materials was investigated using differential thermal analysis, thermal volatilization analysis, programmed vacuum pyrolysis–mass spectrometry, flash pyrolysis–mass spectrometry and off-line pyrolysis–gas chromatography–mass spectrometry. The materials show exothermic degradation after 250 °C. Monitoring the release of hydrogen chloride and water, the blowing agents for the production of carbon foam, clearly indicated the superior performance of the pentavalent phosphorus compound over the trivalent phosphorus compound. The major gaseous degradation products released during pyrolysis showed the presence of sufficient quantities of several alkyl-substituted benzenes and fused aromatics. Suitable degradation mechanism has been proposed and discussed to explain the formation of various organics during thermal degradation.     

Synthesis, characterization and thermal properties of metaloquinolate-containing polymers

The monomer, 5-methyl(2-methacryloylethyloxy)-8-quinolinol(HEMA-CH₂-Hq), which possesses both double bond and 8-hydroxyquinoline groups, was synthesized from 2-hydroxyethyl methacrylate (HEMA) and 5-chloromethyl-8-quinolinol hydrochloride. The model polymer with 8-hydroxyquinoline ligands was obtained by free-radical copolymerization with styrene. So metaloquinolate (AlQ₃, ZnQ₂)-containing polymers are prepared by coordinating reaction with di(8-hydroxyquinoline) aluminum(AlQ₂) chelates or mono(8-hydroxyquinoline) zinc(ZnQ) chelates without cross-linking. Both polymer and polymer complexes were analyzed by FT-IR, UV-vis, DSC, TGA and photoluminescence spectroscopies. They are soluble in common solvents and easy to form films. The use of AlQ₂ and ZnQ avoided the cross-linking caused by the AlQ₃, ZnQ₂ formation between different polymer chains. High glass transition temperature, good thermal stability, and strong yellow-green fluorescence were observed for the prepared polymers. These polymers were expected to have the potential application in yellow-green OLEDs.     

Fluorene-bridged polyphenylquinoxalines with high solubility and good thermal stability: Synthesis and properties

<正>A novel fluorene-bridged tetraketone monomer,9,9-bis[(4-benzilyloxy)phenyl]fluorene(FLTK) was synthesized and characterized.The tetraketone was polymerized with various aromatic tetraamines to afford a series of polyphenylquinoxalines(PPQs).The obtained polymers were found to be soluble in common organic solvents such as N-methyl-2-pyrrolidone(NMP),chloroform and m-cresol.Flexible and tough PPQ films obtained by spin-casting their NMP solutions exhibited tensile strengths higher than 60 MPa.The films also demonstrated good thermal stability up to 500℃in nitrogen and glass transition temperatures higher than 280℃.In addition,the PPQ films exhibited good hydrolytic stability. High surface and volume resistivity retentions were achieved for the films after immersion or boiling in water for 24 h.     

Synthesis and thermal properties of some lithium β-diketonates

Five new volatile lithium complexes were synthesized by reactions of lithium hydroxide monohydrate (LiOH · H₂O) with β-diketones, namely, dipivaloylmethane (HDpm), hexafluoroacetylacetone (HHfa), trifluoroacetylacetone (HTfa), benzoyltrifluoroacetone (HBtfa), pivaloyltrifluoroacetone (HPta), and valeryltrifluoroacetone (HVta). The complexes obtained were studied by IR and electronic absorption spectroscopy, mass spectrometry, and comprehensive thermal analysis. The temperature dependence of the vapor pressure, which was obtained by the Knudsen effusion method with mass-spectrometric analysis of the vapor phase composition in the 400–450 K range, was used to calculate the standard thermodynamic parameters of the Li(Dpm) sublimation: ΔH°_subl = 45.7 ± 1.7 kcal mol^?1 and ΔS°_subl = 77.9 ± 4.0 cal mol^?1 K^?1.     

Synthesis and thermal properties of rigid oxa-bridged-containing dimers and tetramers

Several symmetrical, linear dimers and some star-like tetramers were prepared using easily accessible oxa-bridged derivatives as central rigid cores. In order to produce new liquid crystalline materials various mesogenic/promesogenic groups, containing biphenyl-4,4′-diol, 4,4′-(diazene-1,2-diyl)diphenol and cholesterol sub-moieties, were connected through oxy-ethylene linkers via an ester linkage, in the end-on fashion. Their thermal behaviour and mesomorphic properties were investigated by differential scanning calorimetry (DSC), polarized optical microscope (POM), and variable temperature small-angle X-ray diffraction (XRD) methods. While essentially all the biphenyl-4,4′-diol- and 4,4′-(diazene-1,2-diyl)-based dimeric derivatives exhibited smectic liquid crystalline mesophases, the nature of which are mesogenic groups dependent, none of the cholesterol-containing compounds and tetramers were mesomorphic.