bluuebunny/crossref_metadata_2025 huggingface dataset:
Annealing effect of perfluorosulfonated ionomer membranes on proton conductivity and methanol permeability
Authors: Luan Yinghao , Zhang Yongming , Zhang Heng , Li Lei , Li Hong , Liu Yangang
Published: September 2007

Perfluorosulfonated ionomer (PFSI) was synthesized and PFSI membranes were prepared via a solution‐cast method and annealed at different temperatures from 150 to 230°C. The annealing effect on water content, proton conductivity, and methanol permeability were reported and discussed. X‐ray diffraction and small angle X‐ray scattering were used to test the structure of the membranes. It was found that annealing increased the proton conductivity of the membranes because heat‐treatment helped to free the sulfonic groups that were buried in the polymer segments and form more organized ionic clusters. Water content and methanol permeability of the annealed membranes decreased with increasing annealing temperature. Simultaneously, annealing induced more compact chain packing structure, which eventually affected the transport of the proton and methanol through these ionomer membranes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Water‐dispersible conducting polyaniline/nano‐SiO2 composites without any stabilizer
Authors: Li Xingwei , Dai Na , Wang Gengchao , Song Xiaomei
Published: September 2007

A water‐dispersible conducting polyaniline/ nano‐SiO2 composite, with a conductivity of 0.071 S cm−1 at 25°C, was prepared by the oxidative polymerization of aniline in the presence of amorphous nano‐SiO2 particles. And the structure, morphology, thermal stability, conductivity, and electroactivity of this composite were also investigated. This composite has been steadily dispersed in the aqueous solution for about 10–36 h without the need for any stabilizer. It would significantly impulse the commercial applications of conducting polyaniline/nano‐SiO2 composite as fillers for antistatic and anticorrosion coatings. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Soy protein‐based nanocomposites reinforced by supramolecular nanoplatelets assembled from pluronic polymers/β‐cyclodextrin pseudopolyrotaxanes
Authors: Huang Jin , Zhou Ziyan , Wei Ming , Chen Yun , Chang Peter R.
Published: September 2007

The self‐assembled rigid supramolecular nanoplatelets (SN) from Pluronic polymers with various lengths of polyethylene oxide (PEO) and β‐cyclodextrin have reinforced the soy protein isolate (SPI)‐based biodegradable plastics in terms of strength and modulus but at the expense of elongation. Meanwhile, the water resistance, which limited the application of the SPI plastics, was also enhanced. The structure and properties of nanocomposites were characterized by X‐ray diffraction, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), tensile test, and water uptake test. The low loading of nanoplatelets was able to disperse into SPI matrix homogeneously, which resulted in reinforcement in nanocomposites. With an increase of nanoplatelets loading, the repulsion between nanoplatelets and SPI matrix occurred, accompanying with the formation of rectangle objects, resulted in a decrease of mechanical performance of the nanocomposites. The nanoplatelets with longest free PEO segments produced highest strength with least loss of elongation by virtue of enhanced association with SPI matrix mediated by PEO segments. Meanwhile, the nanoplatelets with moderate length of free PEO segments showed optimal water resistance. Herein, the reinforcing function of a supramolecular nanoplatelet, similar to the structure of layered silicate, was verified. © 2007 Government of Canada. Exclusive worldwide publication rights in the article have been transferred to Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Preparation and characterization of amphiphilic starch nanocrystals
Authors: Song Shiwei , Wang Cai , Pan Zelin , Wang Xiufen
Published: September 2007

In this article, amphiphilic starch nanocrystals were synthesized by graft copolymerization of starch nanocrystals with styrene in aqueous emulsion system. The starch nanocrystals of size around 50 nm were used, which were prepared by acid hydrolysis of corn starch. The structure of starch‐g‐polystyrene nanocrystals was characterized by Fourier transform infrared and 1H nuclear magnetic resonance (1H NMR). The crystalline structure as well as its particle morphology was studied by X‐ray diffraction and scanning electron microscopy, respectively. The results indicated that the amphiphilic starch nanocrystals obtained exhibit the size around 80–100 nm. Its crystalline structure is basically not changed after grafting polystyrene suggested that the polystyrene was essentially grafted on the surface of starch nanocrystals. Wettability experiments indicated that the prepared starch‐g‐polystyrene nanocrystals can be uniformly dispersed both in water phase and oil phase revealing excellent amphiphilicity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Conjugated low‐saturation soybean oil thermosets: Free‐radical copolymerization with dicyclopentadiene and divinylbenzene
Authors: Valverde Marlen , Andjelkovic Dejan , Kundu Patit P. , Larock Richard C.
Published: September 2007

The free‐radical copolymerization of 40–85 wt % of conjugated low‐saturation soybean oil (CLS), and a 9 :1 ratio of acrylonitrile (AN) and either divinylbenzene (DVB) or dicyclopentadiene (DCP) using AIBN as the initiator affords transparent yellow samples, which range from hard to slightly rubbery. DMA analysis indicates that the samples containing DCP have tan δ values ranging from 0.32 to 0.49, while the damping properties of the DVB samples are slightly lower. Extraction analysis shows that complete chemical incorporation of the CLS into the polymeric network is achieved when the original CLS content ranges from 40 to 65 wt %. Lower incorporation of the CLS into the polymer network occurs when the oil content exceeds 70 wt %. In this case, up to 30% of the CLS remains unreacted. These observations are supported by 1H NMR and solid‐state NMR. Thermogravimetric analysis indicates a just one important stage of degradation, implying that the polymer network is highly homogeneous in composition. The temperatures of 10% weight loss for the DCP system range from 402 to 428°C, and from 370 to 391°C for the DVB system. The temperature of maximum degradation ranges from 458 to 518°C for the DCP polymers, and 406 to 422°C for the DVB system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Miscibility and melting behavior of poly(ethylene terephthalate)/poly(trimethylene terephthalate) blends
Authors: Liang Hao , Xie Fang , Chen Biao , Guo Fuquan , Jin Zhen , Luo Fusheng
Published: September 2007

The miscibility and melting behavior of binary crystalline blends of poly(ethylene terephthalate) (PET)/poly(trimethylene terephthalate) (PTT) have been investigated with differential scanning calorimetry and scanning electron microscope. The blends exhibit a single composition‐dependent glass transition temperature (Tg) and the measured Tg fit well with the predicted Tg value by the Fox equation and Gordon‐Taylor equation. In addition to that, a single composition‐dependent cold crystallization temperature (Tcc) value can be observed and it decreases nearly linearly with the low Tg component, PTT, which can also be taken as a valid supportive evidence for miscibility. The SEM graphs showed complete homogeneity in the fractured surfaces of the quenched PET/PTT blends, which provided morphology evidence of a total miscibility of PET/PTT blend in amorphous state at all compositions. The polymer–polymer interaction parameter, χ12, calculated from equilibrium melting temperature depression of the PET component was −0.1634, revealing miscibility of PET/PTT blends in the melting state. The melting crystallization temperature (Tmc) of the blends decreased with an increase of the minor component and the 50/50 sample showed the lowest Tmc value, which is also related to its miscible nature in the melting state. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Interfacial conversion for poly(para‐phenylenevinylene) at a cholesteric liquid crystal surface
Authors: Goto Hiromasa , Miyazawa Tomohisa , Tomishige Keiichi , Kunimori Kimio , Kiebooms Rafaël H. L. , Akiyama Yuki , Akagi Kazuo
Published: September 2007

A new approach for the preparation of poly (para‐phenylenevinylene) (PPV) with an ordered structure is presented. PPV is synthesized by a precursor method using a cholesteric liquid crystal medium. The resultant PPV film is observed to have a cholesteric fingerprint‐like texture, indicating replication of the cholesteric liquid crystal medium. Infrared absorption measurements confirm that the PPV has essentially the same molecular structure as normal PPV film. Ultraviolet–visible absorption measurements show that the absorption band due to π−π* transition of the conjugated main‐chain is located at 402 nm. The conversion is found to occur at the interface with the cholesteric liquid crystal medium as a mechanical process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Influence of prolonging vulcanization on the structure and properties of hard rubber
Authors: Wang Ya , Wang Yiqing , Tian Ming , Zhang Liqun , Ma Jun
Published: September 2007

This research on vulcanization illuminates the structure–property relationship of hard rubber with prolonging vulcanization. At the early stage of curing, polysulfur reacts with styrene–butadiene rubber (SBR) macromolecules to form chemical crosslink, as evidenced by the significant increase of modulus during vulcanization. The chemical crosslink is followed by a large amount of interchain attraction, which is due to the modification of SBR macromolecules by combined sulfur. The combined sulfur is formed by the reaction of sulfur atom with SBR backbone, which improves the polarity of SBR macromolecules since sulfur is polar. The influences of chemical crosslink and interchain attraction on the mechanical properties, thermal properties, dynamic mechanical properties, and fracture morphology were analyzed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Characterization of the viscoelastic and mechanical properties of tightly cross‐linked polythiourethane networks
Authors: Droger Nicolas , Primel Odile , Halary Jean Louis
Published: September 2007

Both viscoelastic behavior and plastic deformation in compression were investigated on new polythiourethane networks based on diisocyanates and tri‐ or tetra‐thiols. Dynamic mechanical analysis was used to characterize the mechanically‐active α and β relaxations as a function of crosslink density and nature of the diisocyanate. Data molecular analysis on these novel materials led to conclusions in good agreement with earlier statements on the well‐known epoxy‐amine networks. Besides, consideration of the relaxational behavior, and especially in the β relaxation region, allowed one to interpret the plastic deformation properties of the systems under study and to predict their poor resistance to fracture. By the way, analysis of the energy required to yield permitted determination of a new characteristic temperature, Ty, which can be compared to the thermomechanical main transition temperature, Tα, and to the glass transition temperature, Tg. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Rapid replication of nanostructures made with a polymer using simple injection molding
Authors: Huang C. K.
Published: September 2007

It is possible to fabricate nanostructures of 25.5 nm by replication using injection molding. In this study, a silicon calibration grating was used as a mold insert to replicate high‐quality nanostructures with a simple custom‐made injection machine. The replicated grating with 25.5‐nm nanofeatures made with a polymer was of high quality when a high mold temperature was employed and the mold was evacuated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Yttrium 90 ibritumomab tiuxetan (Zevalin®): A new bullet in the fight against malignant lymphoma?
Authors: Chapuy Bjoern , Hohloch Karin , Trümper Lorenz
Published: September 2007

Targeted immunotherapy utilizing monoclonal antibodies has improved survival in both indolent and aggressive lymphoma significantly. Since malignant lymphomas are also responsive to radiation, the combination of targeted immunotherapy and radiation with radionuclide coupled to monoclonal antibodies is an attractive option to further improve treatment results. Zevalin is a commercially available variation of the murine anti‐CD20 antibody ibritumomab coupled to Yttrium 90 via the tiuxetan chelator. The development of this novel drug as well as the results of the pivotal studies and clinical strategies to implement this treatment into the routine practice of lymphoma oncology are presented in this review.
Effect of acyl‐CoA oxidase activity on the accumulation of γ‐decalactone by the yeast Yarrowia lipolytica: A factorial approach
Authors: García Erandi Escamilla , Nicaud Jean‐Marc , Belin Jean‐Marc , Waché Yves
Published: September 2007

β‐Oxidation is a cyclic pathway involved in the degradation of lipids. In yeast, it occurs in peroxisomes and the first step is catalyzed by an acyl‐CoA oxidase (Aoxp). The yeast Yarrowia lipolytica possesses several genes (POX) coding for Aoxps. This study is based on the factorial analysis of results obtained with the many POX derivative strains that have been constructed previously. The effect of interactions between Aoxps on the acyl‐CoA oxidase (Aox) activity was important even at the second order. We then investigated the effect of Aox activity on growth and lactone production. Aox activity was correlated with acidification of the medium by cells and with cellular growth but not with lactone production, although Aox activity on short chains was inversely correlated with lactone accumulation. Due to the poor correlation between Aox activity and lactone production, the modeling of this parameter gave no satisfactory results but growth depending on Aox activity was modeled.
Fabrication of lab‐on chip platforms by hot embossing and photo patterning
Authors: Maurya Devendra K. , Ng Wee Yang , Mahabadi Kambiz Ansari , Liang Yen Nan , Rodríguez Isabel
Published: September 2007

In this paper, we review the approaches developed in our laboratory to fabricate polymer‐based microfluidic devices to suit a range of applications in bio‐ or chemical analysis. Thermoplastic materials such as polycarbonate (PC) and poly(methyl methacrylate) (PMMA) are used to fabricate microfluidic devices via hot embossing. To emboss microchannels, we use hard stamps fabricated in silicon or soft stamps molded on poly(dimethylsiloxane) (PDMS). Hard stamps are fabricated on silicon wafers through photolithography and deep reactive ion etching (DRIE). Soft stamps are fabricated by casting PDMS prepolymer on silicon molds. To enclose the fluidic channels, direct fusion bonding was found to produce the highest bond strength with minimal structural deformation. One‐step photolithographic methods have also been explored to produce via photochemical patterning microfluidic structures in photocurable materials. We use the photocurable capabilities of a PDMS copolymer, which incorporates a methacrylate crosslinker. Microfluidic channels are produced via one step‐photopatterning processes by crosslinking the prepolymer mixture through a photomask. The smaller feature size attainable was 100 μm. Structures with higher spatial resolution are fabricated through a photoimprinting process whereby a mold is pressed against the precured mixture during UV crosslinking exposure. The application of the fabricated fluidic devices in electrophoretic ion analysis is also presented.
The future of biomanufacturing in Singapore
Authors: Wong Niki , Yap Miranda
Published: September 2007

Singapore's vision is to become a global biomedical sciences (BMS) hub and to develop the BMS industry as the fourth manufacturing pillar of Singapore's economy. The biomanufacturing industry has been a significant growth area for Singapore's BMS industry, with four major biologics investments totaling close to US$1 billion being committed in less than 2 years and the setting up of local biomanufacturing companies. In parallel, resources in biomedical research and bioprocess manpower capabilities are being built up for this knowledge‐intensive industry. Located at the Biopolis, the epicenter of biomedical R&D, the Bioprocessing Technology Institute (BTI) has been developing bioprocess expertise and programs to support the manpower needs of the growing biomanufacturing sector. With a strong commitment to provide the biomanufacturing industry with research and manpower support, the future looks promising and Singapore is well positioned to become a leading biomanufacturing hub in Asia Pacific.
Defensins: Antimicrobial peptides for therapeutic development
Authors: Verma Chandra , Seebah Shalin , Low Soo Mei , Zhou Lei , Liu Shou Ping , Li Jing , Beuerman Roger W.
Published: September 2007

A novel class of endogenous antimicrobial peptides called defensins has shown great versatility in their activity against a diverse range of microorganisms including bacteria, viruses and fungi. Their mode of action of bacterial cell lysis seems largely nonspecific and so promises to avert the development of resistance. These two features have made them an area of intense research activity and growing commercial interest. A successful multidisciplinary effort to investigate and develop novel defensins analogues has been established in Singapore that involves computer modeling, biochemistry, proteomics, chemical synthesis, molecular biology and clinical sciences.
Lithiumsalze des Tris(trimethylsilylamino)silans ‐ Zur Struktur in Lösung und im Festkörper
Authors: Kosse Peer , Popowski Eckhard , Veith Michael , Huch Volker
Published: September 2007

Lithium Salts of Tris(trimethylsilylamino)silane ‐ Their Structures in Solution and in the Solid State*

Amides, which result from the reaction of tris(trimethylsilylamino)silane (Me3SiNH)3SiH (1) with n‐butyllithium in the molar ratio 1:1 and 1:2 in nonpolar solvents, form a system in which the aminosilane 1, the monoamide (Me3SiNLi)(Me3SiNH)2SiH (2a), the diamide (Me3SiNLi)2(Me3SiNH)SiH (3), and the triamide (Me3SiNLi)3SiH (4) are in equilibrium. When the monoamide 2a is dissolved in THF only the dimeric monolithiated THF adduct 2b is obtained. An X‐ray structure analysis of the lithium silylamide 2b reveals that in the dimeric unit one of the lithium atoms is coordinated by THF, the two lithium atoms thus differing in coordination number (3 versus 4). An X‐ray study of the triamide 4 reveals a centrosymmetric polycycle. Multipole interactions are formed between the lithium and the nitrogen atoms. The reaction of the diamide 3 with chlorotrimethylsilane in boiling THF yields the cis isomer of the cyclic diamide [(Me3SiNLi)(Me3SiNH)SiN(SiMe3)]2· 2 THF (5) as a byproduct. According to an X‐ray structure analysis of 5 the lithium centers are coordinated by one oxygen and three nitrogen atoms, which form a strongly distorted tetrahedron. The interactions between lithium and nitrogen atoms N(1) and N(2), which are part of the four‐membered Si2N2 cycle, have to be considered as weak on the basis of the remarkably long Li‐N distances (233 and 243 pm).
Über dehydrierende Aufbaureaktionen zu silylsubstituierten Alkalimetallgermaniden, ‐stanniden und ‐phosphiden; Molekülstruktur von Neopentasilan
Authors: Lobreyer Thomas , Sundermeyer Wolfgang , Oberhammer Heinz
Published: September 2007

Dehydrogenative Build‐up Reactions to Silyl‐Substituted Alkali Metal Germanides, Stannides, and Phosphides; Molecular Structure of Neopentasilane

The build‐up reaction between monosilane and dispersed sodium or potassium in diethyleneglycol dimethyl ether leads to alkali metal silylsilanides of the composition (Na/K)‐SiH3‐n(SiH3)n (n = 0–3) (1, 1a‐c; 2, 2a‐c). By subsequent reactions with silyl nonafluorobutanesulfonate, C4F9SO3‐SiH3, benzenesulfonic acid, PhSO3H, and methyl p‐toluenesulfonate the corresponding silanes SiH4‐n(SiH3)n (n = 0–4) (3, 3a‐d) and methylsilanes CH3SiH3‐n (SiH3)n (n = 0–3) (4a‐d) were obtained in good yield. The molecular structure of neopentasilane (3d) has been determined by electron diffraction analysis. Treatment of group IV and V hydrides GeH4, PH3, and SnH4 with mixtures of sodium or potassium silylsilanides (1, 1a‐c; 2, 2a‐c) leads to silyl‐substituted sodium or potassium germanides (Na/K)GeH3‐n (SiH3)n (n = 1–3) (5a‐c, 6a‐c), phosphides KPH2‐n(SiH3)n (n = 1–2) (7a‐b), and stannides NaSnH3‐n(SiH3)n (n = 1–3) (8, 8a‐c).
Einfache Lithiumsalze des Tris(trimethylsilylamino)silans
Authors: Gregorzik Ralf , Hartmann Uwe , Vahrenkamp Heinrich
Published: September 2007

Simple Zinc Complexes of Tris(imidazolylmethyl)amine Ligands

The three N‐R‐substituted tris(benzimidazolylmethyl)amine ligands L (1a: R = H, 1b: R = Me, 1c: R = Bz) were used to prepare trigonal‐bipyramidal zinc complexes with varying coligands on the open axial position. Starting with the appropriate zinc salts the complexes ·, and [L· Zn‐ONO2]+ were obtained with various counterions. In the aqua complexes of ligand 1a the water molecules could be replaced by·, acetate, and tosylate. The crystal structure determinations of· and· have revealed a coordination geometry of the L· ZnX cations which is intermediate between tetrahedral and trigonal‐bipyramidal.
Funktionelle Zinkkomplexe von Tris(imidazolylmethyl)amin‐Liganden
Authors: Hartmann Uwe , Gregorzik Ralf , Vahrenkamp Heinrich
Published: September 2007

Functional Zinc Complexes of Tris(imidazolylmethyl)amine Ligands

The three N‐R‐substituted tris(benzimidazolylmethyl)amine ligands L (1a: R = H, 1b: R = Me, 1c: R = Bz) form zinc complexes with biologically active ligands on the fifth coordination site, starting from L, Zn(ClO4)2, and the coligand. The N‐protected amino acids glycine, histidine, and cysteine yield [L· Zn—OCO—CHR—NHAc]ClO4 (2a, 3a, 4a). Aspirin, salicylic acid, and orotic acid are incorporated as [L· Zn‐X]ClO4 (5a—c: X = O‐acetylsalicylate, 6a: X = salicylate, 7a—c: X = orotate). Similarly the sulfonamide furosemide is bound by its carboxylate function in [L· Zn‐Fur]ClO4 (8a—c). The aqua complex resulting from ligand 1a and Zn(ClO4)2 forms hydrogen bonds to nitriles and aldehydes, which has allowed the isolation of [L· Zn—OH2RCN](ClO4)2 (9a: RCN = MeCN, 10a: RCN = PrCN) and of [L· Zn—OH2RCHO](ClO4)2 (11a: RCHO = anisaldehyde, 12a: RCHO = p‐tolualdehyde). The structure determination of the salicylate complex 6a has confirmed the monodentate O‐coordination of the carboxylate substrates to zinc.
, der erste Germanium‐„Iniden”︁‐Komplex
Authors: Schiemenz Berthold , Huttner Gottfried
Published: September 2007

\documentclass{article}\pagestyle{empty}\begin{document}$ \left[ {{\text{Cp'}}\left({{\text{CO}}} \right)_2 {\text{Mn}}\dddot - {\text{GeI}}\dddot - {\text{Mn}}\left( {{\text{CO}}} \right)_2 {\text{Cp'}}} \right]^ - $\end{document}, the First Germanium‐“Inidene” Complex

Im Gedenken an Herrn Dipl.‐Chem. Jochen Heuser.

GeI2 reacts with Na[{Cp′(CO)2Mn}2H] to form the inidenetype compound \documentclass{article}\pagestyle{empty}\begin{document}$ \left[ {{\text{Cp'}}\left( {{\text{CO}}} \right)_2 {\text{Mn}}\dddot - {\text{GeI}}\dddot - {\text{Mn}}\left( {{\text{CO}}} \right)_2 {\text{Cp'}}} \right]^ - $\end{document} (1). The anion 1 contains Ge(0) in a trigonal‐planar coordination, embedded between two Cp′(CO)2Mn groups and an iodo ligand. The intrinsic stability of the cumulene \documentclass{article}\pagestyle{empty}\begin{document}$ \left[ {{\text{Cp'}}\left( {{\text{CO}}} \right)_2 {\text{Mn}} = {\text{Ge}} = {\text{Mn}}\left( {{\text{CO}}} \right)_2 {\text{Cp'}}} \right] $\end{document} is still apparent in the structure of 1: The Ge—Mn bonds are short (229 pm) while the Ge—I distance is rather long (284 pm). The inidene‐type anion 1 can only be obtained from the above‐mentioned reaction if the reaction is quenched by addition of unpolar solvents, thus eliminating starting materials and coproducts. Direct workup of the reation mixture instead leads to [Cp′(CO)2MnGeI3]− (2) as the only isolated product. The transformation of 1 into 2, which contains Ge in the formal oxidation state +2, necessarily implies redox processes, which are well documented in inidene chemistry.
Synthese von C‐substituierten 2,5‐Dihydro‐1H‐borolen (3‐Borolenen)
Authors: Herberich Gerhard E. , Marx Hans‐W. , Wagner Trixie
Published: September 2007

Synthesis of C‐substituted 2,5‐Dihydro‐1H‐boroles (3‐Borolenes)

Magnesium‐diene addition compounds derived from isoprene, 2,3‐dimethylbutadiene, and 1,2‐dimethylenecyclohexane are treated with boron halides BCl2(NR2) (R = Me, Et, iPr), PhBCl2, or MeBBr2 to give C‐substituted 2,5‐dihydro‐1H‐boroles (3‐borolenes) 3–5. In a new in situ procedure 1,3‐pentadiene reacts with Mg/BCl2(NR2) in THF to yield 2‐methyl derivatives 2‐MeC4H5BNR2 (2). The NMe3 adduct of 4,5,6,7‐tetrahydro‐2‐methyl‐2‐boraindan 5e· NMe3 undergoes a topomerization with ΔG290 = 59· 2 kJ/mol in a dissociative‐associative process. The crystal structure of 3,4‐dimethyl‐1‐phenyl‐3‐borolene (4d) has been determined. The molecule displays a classical planar structure. There are no indications for specific intermolecular interactions.
Zink(II)‐Komplexe des Ammonium‐funktionalisierten 2,2′‐Bipyridins [6,6′‐{Me2N(H)CH2C≡C}2bpy](ClO4)2 und des verwandten Liganden 6,6′‐(CH3CH2CH2C≡C)2bpy
Authors: Kövári Endre , Krämer Roland
Published: September 2007

Zinc(II) Complexes of the Ammonium‐Functionalized 2,2′‐Bipyridine [6,6′‐{Me2N(H)CH2C≡C}2bpy](ClO4)2 and of the Related Ligand 6,6′‐(CH3CH2CH2C≡C)2bpy

The 2,2‐bipyridine derivative 6,6′‐(Me2NCH2C≡C)2bpy (1b) was prepared by palladium‐catalyzed C‐C coupling reaction. Protonation of 1b with HX yielded the ammonium salts [6,6′‐{Me2N(H)CH2C≡C}2bpy]X2 (2a, X= NO3−; 2b, X = ClO4−). 2a was characterized by X‐ray crystallography. The complexes (1a)ZnCl2 (3) and [(H21b)ZnCl2](ClO4)2 (4) were obtained by reaction of 2b and the related ligand 6,6′‐(CH3CH2CH2C≡C)2bpy (1a) with ZnCl2. The crystal structure of 3 revealed a tetrahedral coordination of the metal ion by two bipyridine nitrogens and two chloride ligands. Stability constants in acetonitrile/water (19:1) of the 1:1 zinc complexes of 1a and 2a were determined spectrophotometrically. Complexes of [H21b]2+ are of potential interest as model systems for metal‐ammonium cooperativity in the active site of phosphodiesterase enzymes. In acetonitrile/water (19:1) the 1:1‐species [(H21b)Zn] promotes the hydrolysis of bis(p‐nitrophenyl) phosphate more efficiently than [(1a)Zn].
Ethyl‐substituierte 2,5‐Dihydro‐1,2,5‐oxadiborole
Authors: Köster Roland , Seidel Günter , Boese Roland
Published: September 2007

Ethyl‐substituted 2,5‐Dihydro‐1,2,5‐oxadiboroles[1]

Four N‐Lewis base‐(1,2,5‐oxadiboroles) rac‐5(Do) [Do = ammonia (NH3), quinuclidine (Q), pyridine (Py), γ‐picoline (γPic)] of·B(Et)OB(Et)C(Et)=C(Et) (5, identical with II) are prepared by reaction of cis‐Et2BC(Et)=C(Et)BEt2 (A) with KNH2 via the tetraethyl‐substituted (BNBC=C) heterocycles 1‐4.·B(Et)N(SiMe3)B(Et)C(Et)=C(Et) (4) reacts with water with elimination of Me3SiOH to give rac‐5(NH3). The latter undergoes exchange reactions with various N‐bases (Py, γPic, Q) quantitatively forming the 1:1 addition compounds rac‐5(Do) [Do = γPic (X‐ray structure analysis)]. rac‐5(NH3) reacts with Ph3B to yield H3N‐BPh3 and the unstable compound 5, which dimerises to (5)2 and/or reacts with (EtBO) elimination to afford the boroxin (EtBO)3 and, presumably, the nido‐carborane Et4C4B2Et2 (6). ‐ The potassium salt·K[B(Et2)OB(Et)C(Et) = C(Et)] (B) is transformed with ClPbMe3 to EtPbMe3 and presumably 5 or to the rearranged heterocycle·B(Et)OB(Et)C(Et2)C(Et, PbMe3) (7).
Reduktive Spaltung von (Ph2P)2NH und Stabilisierung der Spaltprodukte in einem monoradikalischen Dicobalt(1/2+)‐ und zwei Dicobalt(1+)carbonyl‐Komplexen; Kristallstrukturanalysen der drei neuen Komplexe
Authors: Pohl Diana , Ellermann Jochen , Knoch Falk A. , Moll Matthias , Bauer Walter
Published: September 2007

Chemistry of Polyfunctional Molecules, 115[1]. ‐ Reductive Cleavage of (Ph2P)2NH and Stabilizing of the Cleavage Products in a Mono‐radicalic Dicobalt(1/2 + )‐ and Two Dicobalt(1 + ) Carbonyl Complexes; Crystal Structures of the Three New Complexes*

[Co2(m̈‐CO)2(CO)4(m̈‐dppa)] [5; dppa = (Ph2P)2NH] reacts with dppa (1) in toluene at 85°C within 15 minutes primary to give [Co2(CO)4(m̈‐dppa)2] (6). After about one hour a reductive P‐N bond cleavage of the coordinated dppa in 6 takes place, accompanied by hydrogen transfer, yielding [(Co1+)2(m̈‐CO)(CO)4(dppa−)2] (7), the paramagnetic dinuclear complex [(Co1/2+)2(m̈‐PPh2−)(CO)2(m̈‐dppa)2] (8), and [(Co1+)2(m̈‐CO)(CO)3(m̈‐PPh2−)(m̈‐dppa−)PPh2NH2] (9). The three new compounds 7 ‐ 9 have been characterized by X‐ray analyses, 1H, 13C{1H}‐, 31P{1H}‐NMR, IR, ESR spectroscopy, and magnetic measurements.
Über die Kristallstrukturen der Monofluoroselenite MSeO2F (M = K, Rb, Cs)
Authors: Feldmann Claus , Jansen Martin
Published: September 2007

On the Crystal Structures of the Monofluoroselenites MSeO2F (M = K, Rb, Cs)

The alkali metal monofluoroselenites MSeO2F (M = K, Rb, Cs) have been prepared as single crystals. KSeO2F crystallizes in the space group P21/m and contains distorted trigonalpyramidal SeO2F− anions, the geometry of which has been determined for the first time. These complex anions are bridged by long‐range Se‐F interactions to linear chains. RbSeO2F and CsSeO2F crystallize in the space group Pm3m. In contrast to KSeO2F, the trigonal‐pyramidal SeO2F− anions in these latter two fluoroselenites are disordered. A phase transition between the ordered and disordered modification has been established in the case of KSeO2F. Vibrational spectra have been recorded and are correlated to the results of the crystal structure determination.
Studies of the Reaction Behavior of Nitryl Compounds Towards Azides: Evidence for Tetranitrogen Dioxide, N4O2
Authors: Klapötke Thomas M. , Schulz Axel , Tornieporth‐Oetting Inis C.
Published: September 2007

The reaction behavior of NaN3, AgN3, and Me3SiN3 towards FNO2, CINO2, NO2SbF6, and NO2BF4 was investigated. At ‐30°C or below in a solvent‐free system sodium azide did not react with CINO2, NO2BF4, or NO2SbF6. Below ‐30°C silver azide did not react either with neat C1NO2. Treatment of Me3SiN3 with pure C1NO2 led to the formation of C1N3, N2O, and Me3SiOSiMe3. A mechanism for this reaction has been proposed. Pure chlorine azide was isolated by fractional condensation and identified by its low‐temperature Raman spectrum (liquid state). The reaction of Cp2Ti(N3)2 with C1NO2 also yielded C1N3 as the only azide‐containing reaction product. Treatment of FNO2 with NaN3 at temperatures as low as ‐78°C always ended in an explosion which was probably due to the formation of FN3 as one of the reaction products. The reaction of NO2SbF6 with NaN3 in liquid CO2 (‐55°C· T· ‐35°C) as the solvent afforded a new azide species which was stable at low temperature in solution only and was investigated by means of low‐temperature Raman spectroscopy. The obtained vibrational data give strong evidence for the presence of tetranitrogen dioxide, N4O2, which can be regarded as nitryl azide (NO2N3). The structure and vibrational frequencies of N4O2 were computed ab initio at correlated level (MP2/6‐31 + G*). In liquid xenon (‐100°C· T· ‐60°C) NaN3 did not react with NO2SbF6. A previous literature report on the preparation of N4O2 could not be established.
A New Convenient One‐Step Synthesis of [(SCl)2N]+[SbCl6]− Containing the [(SCl)2N]+ Cation
Authors: Broschag Matthias , Schulz Axel , Klapötke Thomas M.
Published: September 2007

The hexachloroantimonate salt of the [(SCl)2N]+ cation, [(SCl)2N]+[SbCl6]− (1), was prepared in a one‐step reaction from easily available [SCl3]+[SbCl6]− and N(SiMe3)3 and isolated in good yield (60%). The compound was identified by chemical analyses and vibrational spectroscopy (IR, Raman). The geometrical and the vibrational data were also computed ab initio and are in good agreement with the experimental results.
Übergangsmetall‐Silyl‐Komplexe, 5211[1]. Bildung von Kupfer‐Silyl‐ und ‐Stannyl‐Komplexen durch Umsetzung von [Ph3PCuH]6 mit HER3 (E = Si, Sn)
Authors: Schubert Ulrich , Mayer Brigitte , Ruß Claudia
Published: September 2007

Transition Metal Silyl Complexes, 52[1]. ‐ Formation of Copper Silyl and Stannyl Complexes by Reaction of [Ph3PCuH]6 with HER3 (E = Si, Sn)

[Ph3PCuH]6 was used as a source for the Ph3PCu fragment to prepare copper stannyl and silyl complexes. Reaction of [Ph3PCuH]6 with HSnPh3, HSiPh3 or HSiClPh2, respectively, and two equivalents of PPh3 yielded the complexes (Ph3P)3CuER3 (ER3 = SnPh3, SiPh3, SiClPh2).
{6 Lithio(trimethylsilyl)diazomethane· 2 Lithio[4,5‐bis(trimethylsilyl)triazene]· 7 Diethyl Ether}: The First X‐Ray Structure Analysis of a Lithiated Diazoalkane
Authors: Boche Gernot , Harms Klaus , Marsch Michael , Schubert Frank
Published: September 2007

The crystals of {6 lithio(trimethylsilyl)diazomethane· 2 lithio[4,5‐bis(trimethylsilyl)triazene]· 7 diethyl ether} provide for the first time insight into the structure of a lithiated diazomethane, namely that of lithiated (trimethylsilyl)diazomethane (11c). Furthermore, the crystals contain lithiated 4,5‐bis‐(trimethylsilyl)triazene (12), a reaction product of (trimethylsilyl)diazomethane and its Li compound 11c which is analogously found in deprotonation/protonation reactions of other monosubstituted diazomethanes. This structure, together with quantum chemical calculations, leads to a better understanding of the so far rather complex chemistry of lithiated (monosubstituted) diazoalkanes.
Strukturen sterisch überfullter und ladungsgestörter Molekule, 51[1,2]. Oxidative Zersetzung von Tetraisopropyltetrazen: Isolierung und Einkristallstrukturen des Radikalkation‐Salzes [((H3C)2HC)2N‐N=·N‐N(CH(CH3)2)2](SbCl⊖) und des N2‐Eliminierungsproduktes [(H3C)2HC‐HN⊕=C(CH3)2](SbCl⊖)
Authors: Bock Hans , Göbel Ilka , Näther Christian , Solouki Bahman , John Andreas
Published: September 2007

Structures of Sterically Overcrowded and Charge‐Perturbated Molecules, 51[1,2]. ‐ Oxidative Decomposition of Tetra‐isopropyltetrazene: Isolation and Single‐Crystal Structures of the Radical Cation Salt [((H3C)2HC)2N‐N=⊕N‐N(CH‐(CH3)2)2](SbCl⊖) and of the N2 Elimination Product [(H3C)2HC‐HN+=C(CH3)2](SbCl⊖)

The single‐electron oxidation of tetraisopropyltetrazene by the advantageous, oxygen‐free SbCl5/H2CCl2 redox system yields dark‐red crystals of tetraisopropyltetrazenium hexachloroantimonate. Their structure determination at temperatures of 100, 200, and 293 K, the first one of a 2‐tetrazene radical cation, proves a planar skeleton C2N‐N=N‐NC2⊕ with nearly identical NN bond lengths. The reaction of tetraisopropyltetrazene with surplus SbCl5 yields the N2 elimination product isopropylisopropylideneammonium hexachloroantimonate, which also has been crystallized and structurally characterized. Due to the conformation of the C3 subunits perpendicular to each other, the cation (H3C)2HC‐HN⊖ =C(CH3)2 is extremely overcrowded as demonstrated by an angle CNC of 129°. In addition, the thermal decomposition of tetraisopropyltetrazene in the gasphase has been analyzed PE‐spectroscopically, its first and second oxidation potentials have been determined cyclovoltammetrically, and the ESR signal pattern of its radical cation in solution has been recorded and assigned. Based on the experimental data, a possible pathway for the oxidative decomposition of the title compound is discussed.
Aminolyse von 2,5‐Bis(aryloxy)‐3,3aγ4,4‐trithia‐1,6‐diazapentalenen — ein Zugang zu makrocyclischen Heteropentalenen
Authors: Tittelbach Franz , Lutze Gerhard , Graubaum Heinz
Published: September 2007

Aminolysis of 2,5‐Bis(aryloxy)‐3,3aγ4,4‐trithia‐1,6‐diazapentalenes ‐ an Entry to Macrocyclic Heteropentalenes

The N,N′‐bis(3,3aγ4‐trithia‐1,6‐diazapentalenyl)diamines 6, 7 and azacrown ethers 8, incorporating two sulfur‐containing diazapentalenes, have been synthesized from 2,5‐bis(aryloxy)‐3,3aγ4,4‐trithia‐1,6‐diazapentalenes 1 and diamines. The aminolysis of 1 with amines has also been studied providing 2‐monoamino‐ 3 and 2,5‐diaminoheteropentalenes 4.
Substituent Effects on the C‐C Bond Strength, 15[1] Geminal Substituent Effects, 7[2]. Thermochemistry and Thermal Decomposition of Alkyl‐substituted Tricyanomethyl Compounds
Authors: Rakus Klaus , Verevkin Sergej P. , Beckhaus Hans‐Dieter , Rüchardt Christoph
Published: September 2007

The thermolysis reactions of the tricyanomethyl compounds 10a‐c were studied in solution. 2,2‐Dicyano‐3‐methyl‐3‐phenylbutyronitrile (10a) and 2,2‐dicyano‐3‐methyl‐3‐(4‐nitrophenyl)butyronitrile (10b) decomposed heterolytically into carbenium ions and (CN)3C− anions, while 9‐methyl‐9‐(tricyanomethyl)fluorene (10c) underwent about 11% homolytic C‐C bond cleavage into 9‐methyl‐9‐fluorenyl‐ and tricyanomethyl radicals. The rates of the homolysis were determined by a radical scavenger procedure under conditions of pseudozero order kinetics. From the temperature effect on the rate constants the activation parameters were determined [ΔH (10c) = 155· 2 kJ mol−1, ΔS (10c) = 58· 5 J mol−1 K−1]. Standard enthalpies of formation ΔH (g) were determined for 2,2‐dicyanopropionitrile (2) (422.45 kJ mol−1), 2,2‐dicyanohexanenitrile (3) (349.74 kJ mol−1), 2,2‐dicyano‐3‐phenylpropionitrile (4) (540.75 kJ mol−1), 2‐butyl‐2‐methylhexanentrile (5) (‐133.20 kJ mol−1), 2,2‐dimethylpentanenitrile (6) (‐45.78 kJ mol−1), and 2‐methylbutyronitrile (7) (2.44 kJ mol−1) from the enthalpies of combustion and enthalpies of sublimation/vaporization. From these data and known Δ (g) values for alkanenitriles and ‐dinitriles, thermochemical increments for ΔH (g) were derived for alkyl groups with one, two, or three cyano groups attached. The comparison of these increments with those of alkanes reveals a strong geminal destabilization, which is interpreted by dipolar repulsions between the cyano groups. ‐ From ΔH (g) of 10c and ΔH of its homolytic decomposition the radical stabilization enthalpy for the tricyanomethyl radical 1 RSE (1) = ‐18 kJ mol−1 was determined. Thus, 1 is destabilized, in comparison with the RSEs of tertiary α‐cyanalkyl (23 kJ mol−1) and α,α‐dicyanoalkyl (27 kJ mol−1) radicals, which were recalculated from bond homolysis measurements[4] and the new thermochemical data. This change of RSE on increasing the number of α‐cyano groups is discussed as the result of the additive contributions by resonance stabilization and increasing destabilization by dipolar repulsion. The amount of the dipolar energies was estimated by molecular mechanics (MM2).
Gas/Solid Reactions with Acetone
Authors: Kaupp Gerd , Pogodda Uwe , Schmeyers Jens
Published: September 2007

Gas/solid reactions of acetone vapor with neutral organic compounds, salts, or host crystals with strict exclusion of solvents are reported. This gas/solid technique largely avoids waste formation and saves resources. Starting hydrochlorides or hydrobromides are also synthesized by gas/solid techniques. Dihydrohalides of o‐phenylenediamines give 1,5‐benzodiazepines 3, aromatic and aliphatic 1,2‐aminothiols (o‐aminothiophenol, penicillamines, cysteine) yield five‐membered thiazolines and thiazolidines 7, 9, 11, 13. Virtually all carbonyl reagents of the primary amino type 14 give quantitatively the imino derivatives 15 and water. Salt formation may be helpful for increasing melting points and sometimes reactivity as in 8, 10, and 12 if surface passivation has to be overcome. In the case of solid 14 the free bases react equally well. Acetone (2) may be quantitatively removed from exhaust gases by using hydroxylaminium phosphate with formation of free acetone oxime at high flow rates. Inclusion of acetone into various hosts (17‐20, but not 16) is more efficient by imbibition from the gas phase than by crystallization from acetone as the solvent. This advantage may be utilized for gas separations. Some further gases (vapors) coexist in imbibed clathrates whereas others do not. The mechanisms of the gas/solid reactions are elucidated using atomic force microscopy (AFM). Phase rebuildings involve anisotropic movements of molecules over large distances and the formation of characteristic features. In some cases surface hydrates catalyze the gas/solid reaction. Solid‐state mechanisms for imbibition from the gas phase into host crystals with formation of clathrates are similar in nature to those of the covalent reactions. These results are correlated with known X‐ray crystal structures where available.
[2.2](4,7)Isobenzofuranophanes ‐ Synthesis, Characterisation, and Reactivity
Authors: König Burkhard , Ramm Sonja , Bubenitschek Peter , Jones Peter G. , Hopf Henning , Knieriem Burkhard , Meijere Armin De
Published: September 2007

The isomeric Diels‐Alder adducts 3, obtained by cycloaddition of tetraphenylcyclopentadienone to the 4,5:12,13‐bis‐(oxanorbornadieno)[2.2]paracyclophanes syn,syn‐ and anti,‐syn‐2

The stereochemical descriptors syn and anti refer to the orientation of the oxygen bridge in the oxabicyclo[2.2.1]heptadiene subunits with respect to the [2.2]paracyclophaneskeleton.

, yield the unstable isobenzofuranophane 4 by consecutive extrusion of carbon monoxide and tetraphenylbenzene when heated to 180°C. The molecular ion of 4 was observed in the EI mass spectrum. The stable tetraphenyl‐substituted analogue 10 was synthesized independently from the previously unknown 4,5,12,13‐tetrabenzoyl[2.2]paracyclophane (9). UV/Vis as well as fluorescence spectra and an X‐ray crystal structure analysis of 9 are reported.
Chele‐ und Anticheleselektivität, V[1]. Über die Struktur und Chemoselektivität einiger Übergangsmetall‐Derivate von Carbonsäureestern
Authors: Kauffmann Thomas , Möller Thomas , Wilde Heinz‐Wilhelm
Published: September 2007

Chele‐ and Anti‐cheleselectivity, V[1]. ‐ On the Structure and Chemoselectivity of Some Transition Metal Derivatives of Carboxylic Acid Esters

On account of the IR spectra of EtO2CCH2FeCl (2a), EtO2CCH2CoCl (3a), and EtO2CCH(Et)CoCl (3b), prepared in situ by transmetalation of the corresponding Li enolates, and EtO2CCH(Et)CrCl2 (5b), obtained in situ by one‐electron oxidative addition of EtO2CCH(Et)Br to CrCl2, it is assumed that these and similar complexes (2b, 2c, 3c) form 8‐membered cyclic dimers of type 11 in THF in analogy to the Reformatzky reagents. Representatives of these complexes and of corresponding Ti complexes were treated (THF, mol ratio 1:1:1) with substrate pairs, consisting of a normal ketone and a ß‐functionalized ketone (Table 2) or alternatively of a normal ketone and an α‐functionalized ketone (Table 3). In the first case high anti‐cheleselectivity was observed, but in the second case high cheleselectivity. The reasons for this different behaviour are discussed.
Concave Reagents, 15[1]. New Concave 1,10‐Phenanthrolines: Catalysts for the Alcohol Addition to Ketenes and Ligands in Transition Metal Complexes
Authors: Lüning Ulrich , Müller Michael , Gelbert Markus , Peters Karl , Schnering Hans Georg Von , Keller Manfred
Published: September 2007

By bridging tetrahydroxy‐1,10‐phenanthrolines 9 by ditosylates 10 or diiodides 11 concave 1,10‐phenanthrolines 1 were synthesized. Their concave shape was proven by X‐ray analyses of 1a and 1c, their basicities were determined by photometric titrations. Compounds 1a‐g are active in the basecatalyzed addition of alcohols to ketenes and form stable metal ion complexes with transition metal salts.
Synthesis and Properties of Kinetically Stabilized Cyclohepta[def]fluorene Derivatives
Authors: Grieser Udo , Hafner Klaus
Published: September 2007

The dihydrocyclohepta[def]fluorene 18 was prepared by starting from 2,7‐di‐tert‐butylfluorene (11). Deprotonation of 18 furnished the dianion 32− in which the charge is mainly localized at the five‐ and seven‐membered rings as evidenced by NMR investigations. Attempts to oxidize 32− to the uncharged species 3 failed. The ketones 26 and 29 were obtained by regioselective oxidation of 18. Deprotonation of 29 and 26 furnished the anions 4 and 5, respectively, which could be described as cyclohepta[def]fluorenes with a strong donor substituent. 13C‐NMR spectroscopic investigations, however, revealed that 4 is described best as an acyl‐substituted fluorenyl anion. In contrast to this, proof of the existence of the anion 5 could be obtained only from a trapping experiment.
Synthesis of New Alkenyl‐Substituted 2‐(tert‐Butyldimethylsiloxy)‐cyclopropanecarboxylates and Their Diastereoselective Conversion into (Hydroxymethyl)cyclopropanes
Authors: Hofmann Bernhard , Reißig Hans‐Ulrich
Published: September 2007

Various new 2‐alkenyl‐substituted methyl 2‐(tert‐butyldimethylsiloxy)cyclopropanecarboxylates 8‐14 were synthesized from siloxy dienes and methyl diazoacetate. Further substitution by deprotonation and reactions with electrophiles provided derivatives 15‐19 in good yields. Reduction of trans‐configurated cyclopropanecarboxylates with LiAlH4 afforded the corresponding trans‐2‐(tert‐butyldimethylsiloxy)‐1‐(hydroxymethyl)cyclopropanes in excellent yields. The related cis‐compounds were not formed, but ring‐opened products derived thereof were isolated. This unexpected influence of the configuration of the starting material on the type of the product formed is discussed.
Characteristic Reactions of 4‐Siloxy‐2,5‐dihydrooxepines: Desilylation, [2 + 2] and [4 + 2] Cycloadditions
Authors: Hofmann Bernhard , Reißig Hans‐Ulrich
Published: September 2007

Desilylation of 4‐siloxy‐2,5‐dihydrooxepine 1 with NEt3· HF afforded oxepinone 2. [2 + 2] Cycloadditions of 1 and methyl‐substituted derivative 4 to tetracyanoethylene provided bicyclic products 3 and 5, respectively. Hetero Diels‐Alder reactions of 2,5‐dihydrooxepines 1 and 9 with 1,1,1‐trifluoro‐2‐nitrosopropene furnished the corresponding bicyclic 1,2‐oxazines 8 and 10, resp., in reasonable yields. The considerably higher reactivity of the silyl enol ether unit compared with the endocyclic enol ether moiety as revealed by these cycloadditions is discussed.
Sterically Hindered Double‐Bond Systems, VII[1l]. On the Reaction of Succinic Esters with tert‐Butyllithium
Authors: Hopf Henning , Hänel Ralf
Published: September 2007

Addition of tert‐butyllithium to dimethyl (1a) and diethyl succinate (1b), respectively, provides 2,2,7,7‐tetramethyl‐3,6‐octanedione (3) in good yield as well as the ketoesters 5a/b and the cyclized products 6 and 7. The mode of formation of these latter side products is discussed, and several published errors concerning these transformations are corrected.
1,2‐Bis(diisopropylamino)‐1,2‐dihydro‐1,2‐benzodiboret ‐ ein erstes thermisch stabiles 1,2‐Dihydro‐1,2‐diboret
Authors: Kaufmann Dieter E. , Boese Roland , Scheer Alexander
Published: September 2007

1,2‐Bis(diisopropylamino)‐1,2‐dihydro‐1,2‐benzodiborete ‐ A First Thermally Stable 1,2‐Dihydro‐1,2‐diborete*

The synthesis of 1,2‐bis(diisopropylamino)‐1,2‐dihydro‐1,2‐benzodiborete (7) suceeds in good yield by a twofold ipso‐borylation of 1,2‐bis(trimethylsilyl)benzene to give 3, double amination to afford 4 and subsequent coupling with sodium/potassium alloy. Crystalline 7 is thermally stable; an X‐ray crystallographic structure determination has been carried out. In concentrated solution reaction of 4 with sodium/potassium alloy predominantly leads to the formation of the tetraborocine 6 by dimerization. In the presence of (phthalocyaninato)palladium as catalyst 7 reacts with 2 equivalents of dimethylacetylenedicarboxylate to give the benzo‐annulated diborocine 12.
Addition von Aldehyden an aktivierte Doppelbindungen, XXIX1) Neue Methode zur Darstellung symmetrischer 1,4‐Diketone
Authors: Stetter Hermann , Bender Hans‐Jürgen
Published: September 2007

Phenyl‐vinyl‐sulfon reagiert unter Thiazoliumsalz‐Katalyse mit aliphatischen, aromatischen und heterocyclischen Aldehyden in einem dreistufigen Additions‐Eliminierungs‐Mechanismus zu 1,4‐Diketonen (1–3) und dem 1,4‐Disulfon (23). Bei Verwendung von Divinyl‐sulfon werden in guter Ausbeute die entsprechenden 1,4‐Diketone (1–1) erhalten.