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Starting Materials (starting + material)
Kinds of Starting Materials Selected AbstractsSynthesis of Some New Azole, Azepine, Pyridine, and Pyrimidine Derivatives Using 6-Hydroxy-4H-4-oxo[1]-benzopyran-3-carboxaldehyde as a Versatile Starting Material.CHEMINFORM, Issue 22 2005A. H. Abdel-Rahman No abstract is available for this article. [source] Syntheses of 1,2,3,4,6,7,12,12b-Octahydroindolo[2,3-a]quinolizine and Harmicine Using a Chiral 1-Allyl-1,2,3,4-tetrahydroxy-,-carboline as the Starting Material.CHEMINFORM, Issue 50 2004Takashi Itoh Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Bis-Cyclopentadienyl Nickel (Nickelocene): A Convenient Starting Material for Reactions Catalyzed by Ni(0) Phosphine Complexes.CHEMINFORM, Issue 15 2002Nicholas E. Leadbeater Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Synthesis of New 1,4-Dihydropyridines by Addition-Rearrangement Process with Imine Derivatives and ,-Ketoester as Starting Materials in Solvent-Free Conditions.CHEMINFORM, Issue 35 2009Xueming Chen Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: ,-Nitroacrylates and Silyl Enol Ethers as Key Starting Materials for the Synthesis of Polyfunctionalized ,-Nitro Esters and 1,2-Oxazine-2-oxides.CHEMINFORM, Issue 33 2009Roberto Ballini Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Convenient Preparation and Full Characterization of a Synthetically Useful Salt of the Dithianitronium Cation, SNSSbF6, from Readily Available Starting Materials.CHEMINFORM, Issue 49 2005T. Stanley Cameron Abstract For Abstract see ChemInform Abstract in Full Text. [source] Cu[Al(ORF)4] Starting Materials and their Application in the Preparation of [Cu(Sn)]+ (n=12, 8) ComplexesCHEMISTRY - A EUROPEAN JOURNAL, Issue 27 2009Gustavo Santiso-Quiñones Dr. Abstract Naked copper,? A newly developed simple two-step route to weakly coordinated CuI starting materials that were used to prepare novel copper,cyclosulfur adducts, including the first M+,S12 complex (see figure, RF= C(CF3)3, C(CH3)(CF3)2, or CH(CF3)2). Reactions with the [Al{OC(CF3)3}4], counterion mimic gas-phase chemistry inside a mass spectrometer (to form [Cu(S12)]+). An effective route to stable, almost-"naked" CuI salts of weakly coordinating anions (WCAs) of the type [Al(ORF)4], has been developed. Born,Fajans,Haber cycles and theoretical calculations suggest that this methodology is useful for the generation of CuI salts regardless of the larger WCA used. The first homoleptic CuI,arene complex [Cu(1,2-F2C6H4)2]+[Al{OC(CF3)3}4], (1), the first CuI,methylenechloride complex [Cu(CH2Cl2)Al{OC(CH3)(CF3)2}4] (2), and the donor-free dimer [CuAl{OCH(CF3)2}4]2 (3) were synthesized in quantitative yields by sonicating Li[Al(ORF)4] (RF=C(CF3)3, C(CH3)(CF3)2, or CH(CF3)2), AgF, and a three-fold excess of CuI in 1,2-F2C6H4 (1) or CH2Cl2 (2, 3). Substances 1,3 are good starting materials for further CuI chemistry, and the reaction of 1,3 with the weak Lewis base cyclooctasulfur gave the first CuI,sulfur complexes of type [Cu(S12)(S8)]+[Al{OC(CF3)3}4], (4), [Cu(CH2Cl2)(S12)]+[Al{OC(CF3)3}4], (5), [A1Cu(1,5-,1,,1 -S8)CuA1] (6; A1=[Al{OC(CH3)(CF3)2}4],), and a CuI,S8 1D coordination polymer with [Cu2(S8)2A22] (7; A2=[Al{OCH(CF3)2}4],), as a monomeric repeat unit. Complexes 4 and 5 are the first example of any metal coordinated to cyclo-S12 and 4 is the first example of a complex having an element in two allotropic modifications as a ligand. [source] 1-Alkynylphosphines and Their Derivatives as Key Starting Materials in Creating New PhosphinesCHEMISTRY - AN ASIAN JOURNAL, Issue 3 2010Azusa Kondoh Abstract This Focus Review summarizes transformations of 1-alkynylphosphines and their derivatives directed toward the synthesis of new phosphines. Owing to the importance of organophosphines as ligands for transition metal catalysts, development of efficient methods for the synthesis of new phosphines is quite important. 1-Alkynylphosphines and their derivatives have been emerging as useful precursors for the creation of new phosphines. Chemical modifications of the carbon,carbon triple bonds, including nucleophilic addition and cycloaddition, lead to a wide range of new useful phosphines that are otherwise difficult to synthesize. [source] Mechanical activation of precursors for nanocrystalline materialsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 1 2003H. Heegn Abstract Nanostructured materials win big scientific interest and increasingly economic meaning through their specific exceptional properties. Precursors that were compacted by pressing and sintering are normally used preparation of materials. In present work, the influence of mechanical activation by grinding on the structure as well as on compacting and sintering behavior of oxides from magnesium, aluminium and silicon has been investigated. Starting materials for each metal oxide differ in microstructure, dispersity, and porosity. The influence of mechanical activation on the destruction of crystalline structure to nanocrystalline, as well as to the amorphous stage and the compaction of powders with nano-particles, as well as structures with nanoscale pores have been compared. The possibilities of the consolidation of nanostructured materials were investigated. The mechanical activation took place in a disc vibration mill. The mechanical activated materials as well as their pressing and their sintering products were characterized by density, particle-sizedistribution, specific surface, pore-structure, microstructure, and crystallite size by X-ray powder diffraction (XRD). The mechanical activation of the model-substances led, in most cases, to an improvement of the compaction properties; thus, this improvement can be achieved with subsequent sintering densities up to 98% of the theoretical density. From these experiments, generalizations transferable to other materials can be made. [source] TOOLS TO QUALIFY EXPERIMENTS WITH BLOOMERY FURNACES*ARCHAEOMETRY, Issue 1 2010M. SENN Five experimental bloomery iron ore smelts were carried out in a reconstruction of an early medieval furnace of the Boécourt type (Switzerland). A part of the bloom from the most successful experiment was forged to a billet. Starting materials and products were weighed, described and chemically characterized (ICP-MS, LA-ICP-MS and WD-XRF). The calculation of the yield and mass balance based on the chemical analyses from the ore (optimum) and from the ore, furnace lining, slag and ash (applied) allow the determination and quantification of the materials involved in the process. This permits the interpretation of the quality of the experiments. The chemical characterization of metal produced from hematite ore from the Gonzen Mountains in Switzerland gives archaeologists the possibility to compare the metal of iron artefacts to metal from this mine. Finally a good agreement between experiments and archaeological reality can be shown. [source] Influence of the atmosphere on the growth of LiYF4 single crystal fibers by the micro-pulling-down methodCRYSTAL RESEARCH AND TECHNOLOGY, Issue 2 2009D. Maier Abstract Micro-pulling-down growth of LiYF4 single crystal fibers have been performed under different gas atmospheres using stoichiometric LiYF4 single crystal pieces from prior Czochralski experiments as starting material. Completely transparent and phase pure LiYF4 single crystal fibers could be obtained after evacuation of the recipient to 2×10 -6 mbar and subsequent filling with pure (99.995%) CF4 gas. Using a gas mixture of 5% CF4 in Argon or pure 5N Argon leads to the formation of micro crystallites of oxofluorides on the surface. Evacuating only to 3 × 10 -3 mbar leads, independently of atmosphere, to completely white fibers that are heavily contaminated with oxofluorides. DSC measurements of the completely transparent fiber grown under pure CF4 atmosphere reveal congruent melting behavior. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] MS-TOF Study of the Formation of Thiolato-Bridged Rhodium OligomersEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2010Josée Boudreau Abstract The complex [Cp*Rh(,-SPh)3RhCp*]Cl was used as a starting material to synthesize various oligomeric materials of the general formula [Cp*Rh(,-SPh)x(,-Cl)3,x{Rh(,-SPh)3}nRhCp*] (x = 1 to 3; n = 1 to 4), which are formally formed by insertion of nRh(SPh)3 units into one ,-Rh,SPh bond. The insertion of Ir(SPh)3 was also observed to generate theheterotrimetallic species. All complexes were observed by using HRMS-TOF and [Cp*Rh(,-SPh)3Rh(,-SPh)3RhCp*]Cl, [3+]Cl, was characterized by using X-ray crystallography. [source] Dynamic Enzymatic Kinetic Resolution of Methyl 2,3-Dihydro-1H -indene-1-carboxylateEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 35 2009Jörg Pietruszka Abstract A new reaction setup for kinetic enzymatic resolution was established and is demonstrated for the case of the hydrolase-catalysed conversion of methyl 2,3-dihydro-1H -indene-1-carboxylate (1) in conjunction with a base-catalysed racemisation. The system allows controlled racemisation, resulting in efficient dynamic kinetic resolution (DKR) of the title compound. Short reaction times and high enantioselectivities were obtained with CAL-B and TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene). Compound (R)- 1 (ee 95,%) served as a starting material in a domino reaction that led to the biaryl indanyl ketone (R)- 8, a lead compound for novel inhibitors of peptidyl-prolyl- cis/trans -isomerases, in 94,% ee. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Ilicic Acid as a Natural Quiron for the Efficient Preparation of Bioactive ,- and ,-EudesmolEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 21 2009Alejandro F. Barrero Abstract An efficient procedure for the isolation of the sesquiterpene ilicic acid (3) on a multigram scale of extracts obtained from aerial parts of Inula viscosa (Asteraceae) was developed. Acid 3 is an appropriate starting material for short, enantiospecific syntheses of ,-eudesmol (1) and ,-eudesmol (2), natural products featuring significant antiangiogenic and anti-Alzheimer properties. Synthesis of 1 was achieved in six steps and the synthesis of 2 in seven, producing overall yields of 52 and 41,%, respectively.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Asymmetric Synthesis of (S)-Mirtazapine: Unexpected Racemization through an Aromatic ipso -Attack MechanismEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2008Marco van der Linden Abstract An asymmetric synthesis of (S)-mirtazapine has been achieved from the synthesis of the racemate by using (S)-1-methyl-3-phenylpiperazine as the starting material. Unfortunately, significant racemization was encountered in the final step, which involved an electrophilic aromatic ring closure of a alcohol by concentrated sulfuric acid. A significantly higher ee was observed when polyphosphoric acid (PPA) was used instead. A remarkable correlation between the amount of PPA used and the ee of the product was revealed, namely, an increase in the ee upon decreasing the amount of PPA. This trend was paralleled by the formation of an increasing amount of a side-product upon lowering the amount of PPA. The racemization and formation of a side-product can be explained by an ipso -attack mechanism during the electrophilic aromatic ring-closure reaction. This mechanism was supported by a mechanistic study using a deuterium-labeled substrate.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Thermodynamic Study of ,H Complexes in Nucleophilic Aromatic Substitution Reactions: Relative Stabilities of Electrochemically Generated RadicalsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 14 2008Iluminada Gallardo Abstract The mechanism for the electrochemical oxidation of ,H complexes, such as 1-hydro-1-alkoxy/sulfoxy or -fluoro-2,4-dinitro/2,4,6-trinitrocyclohexadienyl anions, has been widely studied by means of cyclic voltammetry and controlled-potential electrolysis. Previous studies have shown that the electrochemical oxidation of ,H complexes, formed by the addition of carbon or nitrogen nucleophiles followed by a two electron mechanism, corresponding to the formal elimination of the hydride anion (nucleophilic aromatic substitution of hydrogen mechanism, the NASH mechanism). For these ,H complexes (Nu, = OH,, ,OR, ,SR, ,F), the electrochemical reaction takes place by a one-electron mechanism and is followed by the radical elimination of the leaving group with the consequent recovery of the starting material. This mechanism is similar to that proposed for the electrochemical oxidation of ,X complexes (nucleophilic aromatic substitution of a heteroatom, the NASX mechanism). The operating mechanism in each case, the NASH or NASX, can be rationalized in terms of thermodynamics. The standard potentials of the , complex and/or the leaving group as well as the bond dissociation energies (BDEs) are determinant factors. This study has not led to a significant improvement in the electrochemical preparation of aromatic-substituted compounds, but does help to understand and predict the usefulness or uselessness of using the nucleophilic aromatic substitution route to obtain a desired product. Finally, the current approach extends the electrochemical methodology to different chemical fields, for example, to general nondestructive methods for the detection, identification, and quantification of either organic pollutants or explosives in different solvents. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Anisotropic Behavior of Radiopaque NiTiPt Hypotube for Biomedical ApplicationsADVANCED ENGINEERING MATERIALS, Issue 11 2009Zhicheng Lin This paper presents the first characterization of anisotropic stress,strain behavior in micron-sized specimens cut directly from hypotubes, the starting material for the manufacture of endovascular stents and other biomedical devices, of a new radiopaque alloy NiTiPt. Experimental results show that NiTiPt hypotube has very different anisotropic characteristics when compared to its NiTi counterpart including higher tensile strength and strain, higher stress,strain nonlinearity, smaller hysteresis loop, and sharper tails during loading,unloading. [source] Ex-Chiral-Pool Synthesis of ,-Hydroxyphosphonate Nucleoside AnaloguesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2007Franck Gallier Abstract A new series of mononucleotide analogues bearing a nonhydrolysable P,C bond instead of the P,O phosphate linkage is presented. We intend to set up an approach that allows the synthesis of ,-hydroxyphosphonate nucleoside analogues as a single diastereoisomer. In this respect, the key "sugar-phosphonate" intermediate was obtained through an Arbusov reaction from an iodosugar derivative in which the stereochemistry of the ,-hydroxy group is determined by the choice of the starting material and remains in the resulting nucleotide analogues. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] First Propargyl Azides Bearing Strong Acceptor Substituents and Their Effective Conversion into Allenyl Azides: Influence of the Electronic Effects of Substituents on the Reactivity of Propargyl Azides,,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2005Joseph Rodolph Fotsing Abstract We have succeeded in the synthesis of propargyl azides containing 1- or 3-phenylthio functionalities. The selective oxidation of their sulfur atoms to sulfoxides and sulfones allows access to the first propargyl azides bearing acceptor substituents. Interestingly, the prototropic rearrangement of the latter propargyl azides leads to the formation of allenyl azides with relatively high stabilities and with moderate to good yields. Propargyl azides containing phenylthio functionalities react in the presence of nucleophiles to afford the expected N -unsubstituted 1,2,3-triazoles via short-lived allenyl azides. These results are entirely different from those of the corresponding sulfoxides and sulfones, which react under the analogous conditions either to produce the corresponding bis(triazolo)pyrazine derivatives or to yield newly substituted vinyl azides. The latter compounds can successfully be used as starting material providing access to azirines. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] One-Pot Preparation of [n]Ladderanes by [2, + 2,] PhotocycloadditionEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 3 2005Henning Hopf Abstract A new method for the preparation of [n]ladderanes is presented, based on a one-pot [2,+2,] photocycloaddition of [2.2]paracyclophane pseudo- gem bis(polyene) precursors. [3]- and [5]ladderanes could be isolated and were fully characterized, including their X-ray structure analysis. The overall chemical yields from [2.2]paracyclophane as starting material were found to be 53 % ([3]ladderane) and 38 % ([5]ladderane). Preliminary investigations of their photochromic properties (reversible change from yellow or red to colourless forms) are described. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Competition between Non-Classical Single and Double Epimerizations in Cyclitol ChemistryEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 9 2004Ralf Miethchen Abstract Two competitive regio- and stereoselective epimerization reactions were investigated in four cyclitols characterized by four contiguous OH groups with a cis - trans - trans sequence and by varied substituents (OMe, OBz, F, H) adjacent to this tetrol unit. The starting materials were synthesized from L -quebrachitol (compounds 5,7) and myo -inositol (compound 8). Their acetalization with the chloral/DCC reagent system gave cyclic acetals with one epimerized chiral ring atom and also with two epimerized chiral centres. The single epimerization takes place exclusively at the middle C-atom of the cis - trans triol unit in the tetrol sequence (products 15, 17, 19/20 and 24,27), whereas the double epimerization occurs at both of the "centrally located" C-atoms in the cis - trans - trans tetrol unit (products 16, 18, 21 and 28). The product ratios of singly to doubly inverted compounds change as follows: the lower the electron-withdrawing effect of the substituents adjacent to the tetrol unit, the higher the percentage of the corresponding doubly inverted product. However, the singly inverted products remain the major products in all cases. X-ray analyses are given for the starting material 1-fluoro-2- O -(methyl)cyclohexane-2,3,4,5,6-pentol (5) and for the products 1- O -cyclohexylcarbamoyl-2,3- O -(2,2,2-trichloroethylidene)5- O -(methyl)cyclohexane-1,2,3,4,5-pentol (17), 3- O -acetyl-1- O -benzoyl-6- O -cyclohexylcarbamoyl-2- O -methyl-4,5- O -(2,2,2-trichloroethylidene)- muco -inositol (22) and 2,3-di- O -ethylidene)-(+/-)- chiro -inositol (24). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Cytochrome b559 content in isolated photosystem II reaction center preparationsFEBS JOURNAL, Issue 10 2003Inmaculada Yruela The cytochrome b559 content was examined in five types of isolated photosystem II D1-D2-cytochrome b559 reaction center preparations containing either five or six chlorophylls per reaction center. The reaction center complexes were obtained following isolation procedures that differed in chromatographic column material, washing buffer composition and detergent concentration. Two different types of cytochrome b559 assays were performed. The absolute heme content in each preparation was obtained using the oxidized-minus-reduced difference extinction coefficient of cytochrome b559 at 559 nm. The relative amount of D1 and cytochrome b559,-subunit polypeptide was also calculated for each preparation from immunoblots obtained using antibodies raised against the two polypeptides. The results indicate that the cytochrome b559 heme content in photosystem II reaction center complexes can vary with the isolation procedure, but the variation of the cytochrome b559,-subunit/D1 polypeptide ratio was even greater. This variation was not found in the PSII-enriched membrane fragments used as the RC-isolation starting material, as different batches of membranes obtained from spinach harvested at different seasons of the year or those from sugar beets grown in a chamber under controlled environmental conditions lack variation in their ,-subunit/D1 polypeptide ratio. A precise determination of the ratio using an RC1-control sample calibration curve gave a ratio of 1.25 cytochrome b559,-subunit per 1.0 D1 polypeptide in photosystem II membranes. We conclude that the variations found in the reaction center preparations were due to the different procedures used to isolate and purify the different reaction center complexes. [source] Boosting the Non Linear Optical Response of Carbon Nanotube Saturable Absorbers for Broadband Mode-Locking of Bulk LasersADVANCED FUNCTIONAL MATERIALS, Issue 12 2010W. B. Cho Abstract Single-walled carbon-nanotube absorbers are experimentally demonstrated for laser mode-locking. A saturable absorber device is used to mode-lock three different bulk solid-state lasers in a 500,nm-wide wavelength interval. The devices exhibit a low saturation fluence of <10,µJ cm,2, low scattering losses, and an exceptionally rapid relaxation, with time constants reaching <100 fs. The latter two properties are explained by a decreased curling tendency and increased tube-to-tube interactions of the nanotubes, respectively. These properties are the result of an optimized manufacturing procedure in combination with the use of a starting material with a higher microscopic order. The decreased scattering enables universal use of these devices in bulk solid-state lasers, which tend to be highly sensitive against non-saturable device losses as caused by scattering. The favorable saturable absorption properties are experimentally verified by mode-locking the three lasers, which all exhibit near transform-limited performance with about 100 fs pulse duration. The complete and unconditional absence of Q-switching side bands verifies the small saturation fluence of these devices. [source] Flammability studies of sodium thiosulphate or metabisulphite impregnated wood using cone calorimeterFIRE AND MATERIALS, Issue 2 2007imkovic Abstract Spruce wood boards impregnated with Na2S2O3 or Na2S2O5 were studied with the cone calorimeter. The presence of Na2S2O3 lowered the average heat release rate in comparison to untreated material. The total amounts of CO and CO2 production were reduced by the treatment and also the specific extinction area and mass loss rate decreased. Washing of the salt from the material with water caused partial loss of the properties. Addition of the second impregnation step using acids (HCOOH, H3BO3 or H3PO4) resulted in the fixation of the sulphur in wood, but gave not the results of single-step modification for thiosulphate. With Na2S2O5 and without acid, the CO and time-to-ignition values were higher and average heat release rate smaller in comparison to unmodified material. Combined one step Na2S2O5/H3BO3 treatment lowered the CO, CO2 and specific extinction area values in comparison to the modification with Na2S2O5, similarly like it was observed for Na2S2O3/H3BO3 two-step-treatment. According to time-to-ignition values, Na2S2O5 alone at 5% addition is a better flame retardant than Na2S2O3 at 7%, but the effect is diminished at 10% amount or presence of acids. The total smoke release curves showed decrease due to modification in both phases of the process. Introduction of water washing as well as the acid treatment further lowered the values. The best results were achieved with 15% Na2S2O3,2% H3PO4,H2O system. According to the total smoke release curve the specimen produced more than five times smaller amount of smoke than untreated material in the first phase of the process. It seams that the concentration of Na2S2O5 is less affecting the properties than the synergistic effect of the Na2S2O3 or Na2S2O5/H3BO3 system. Although the level of smoke is low, the presence of elemental sulphur causes smaller times-to-ignition than on starting material. Copyright © 2006 John Wiley & Sons, Ltd. [source] Olfactory properties of straight-chain undecan -x- ones, undecan -x- ols (x = 2,6) and their derivativesFLAVOUR AND FRAGRANCE JOURNAL, Issue 3 2008Julia Gibka Abstract A series of undecan -x- ones (x = 2,6) was used as starting material in the synthesis of ethylene and propylene acetals, undecanols and their acetates. Undec-3-yl and undec-6-yl acetates, ethylene acetal of undecan-3-one and propylene acetals of undecan -x- ones (x = 2,5) have not yet been described. The odour properties for all the synthesized compounds have been determined. They have pleasant, fruity, herbaceous odours that can be described as food odours. The most valuable groups of compounds are ketones and their acetals, which have intense, pleasant, fruity, vegetable, spicy or herbaceous odours. In the case of alcohols, mild odours dominate with fruity, wooden or floral notes. All acetates have faint or mild fatty-soapy odours. A correlation between the structure of the studied compounds and their odours has been found. Fruity odours appear among ketones and alcohols when a shift of the functional group from position 2 to the middle of the molecule occurs. In the studied ethylene and propylene acetals this shift strengthens their vegetable and spicy odours, respectively. Copyright © 2008 John Wiley & Sons, Ltd. [source] Functional Chromium Wheel-Based Hybrid Organic,Inorganic Materials for Dielectric ApplicationsADVANCED FUNCTIONAL MATERIALS, Issue 20 2009Vito Di Noto Abstract The first example of organic,inorganic hybrid materials based on the embedding of a chromium,nickel wheel cluster {[(n-C3H7)2NH2]- [Cr7NiF8(O2C4H5)16]} (Cr7Ni) into poly(methyl methacrylate) (PMMA) and the characterization of the dielectric properties of the obtained material is described. By an optimized copolymerization of the methacrylate-functionalized chromium,nickel wheel with methyl methacrylate in a cluster/monomer 1:200 molar mixture, a homogeneous hybrid material CrNi_MMA200 is obtained. The electrical responses of the non-doped PMMA and of the hybrid material were studied by broadband dielectric spectroscopy (BDS) from 0.01,Hz to 10,MHz and over the temperature range of 5,115,°C. The permittivity profiles reveal two relaxation peaks in the materials, which correspond to the , and , relaxation modes of the PMMA matrix. The position of these modes shifts toward higher frequencies as temperature increases. BDS is a powerful tool revealing the intimate miscibility of the various components of the hybrid material, thus indicating that, on a molecular scale, the material proposed is a homogeneous system. Finally, a value of the dielectric constant of 2.9 at 25,°C and 1,kHz is determined. This value is noticeably lower than the value of 3.2 obtained for pristine PMMA prepared following the same synthesis protocol. Thus, these results classify the hybrid CrNi_MMA200 as an appealing starting material for the development of dielectric polymeric layers for the development of innovative capacitors, transistors, and other microelectronic devices. The vibrational properties of the hybrid materials are investigated by Fourier-transform infrared (FT-IR) and Raman spectroscopy, whereas the thermal behavior is analyzed by thermogravimetric analysis (TGA). Swelling experiments are used to qualitatively evaluate the crosslinking density of the hybrid materials. The integrity of the wheels once embedded in the macromolecular backbone is confirmed by extended X-ray absorption fine structure (EXAFS) and electron spin resonance (EPR) spectroscopic measurements. [source] Total Synthesis of Murrayanine Involving 4,5-Dimethyleneoxazolidin-2-ones and a Palladium(0)-Catalyzed Diaryl InsertionHELVETICA CHIMICA ACTA, Issue 8 2007Pablo Bernal Abstract A new total synthesis of the natural carbazole murrayanine (1) was developed by using the 4,5-dimethyleneoxazolidin-2-one 12 as starting material. The latter underwent a highly regioselective Diels,Alder cycloaddition with acrylaldehyde (=prop-2-enal; 13) to give adduct 14 (Scheme,3). Conversion of this adduct into diarylamine derivative 9 was carried out via hydrolysis and methylation (Scheme,4). Differing from our previous synthesis, in which such a diarylamine derivative was transformed into 1 by a PdII -stoichiometric cyclization, this new approach comprised an improved cyclization through a more efficient Pd0 -catalyzed intramolecular diaryl coupling which was applied to 9, thus obtaining the natural carbazole 1 in a higher overall yield. [source] Diradical-Promoted Two-Carbon Ring-Expansion Reactions by Thermal Isomerization: Synthesis of Functionalized Macrocyclic KetonesHELVETICA CHIMICA ACTA, Issue 7 2004Georg Rüedi A new method for the smooth and highly efficient preparation of functionalized macrocyclic ketones has been developed. Pyrolysis of medium- and large-ring 3-vinylcycloalkanones by dynamic gas-phase thermo-isomerization (DGPTI) at 600,630° yielded, under insertion of a previously attached vinyl side chain by means of a 1,3-C shift, the corresponding ,,, -unsaturated cycloalkanones. The yield of the two-carbon ring-expanded ketones greatly depended on the relative ring strains of substrate and product (5,87%, cf. Table,5). The formation of minor amounts of one-carbon ring-expanded cycloalkenes (<10%) can be ascribed to a subsequent decarbonylation step. A reaction mechanism involving initial cleavage of the weakest single bond in the molecule has been established (cf. Scheme,6). Recombination within the generated diradical intermediate in terminal vinylogous position led to the observed products, while reclosure gave recovered starting material. Substituents on the vinyl moiety were transferred locospecifically into the ring-expanded products. An isopropenyl group did not significantly affect the isomerization process, whereas substrates bearing a prop-1-enyl group in , -position enabled competing intramolecular H-abstraction reactions, leading to acyclic dienones (cf. Schemes,9,11). DGPTI of the 13-membered analogue directly yielded 4-muscenone, which, upon hydrogenation, led to the valuable musk odorant (±)-muscone. Increasing the steric hindrance on the vinyl moiety gave rise to diminishing amounts of the desired ,,, -unsaturated cycloalkanones. This novel two-carbon ring-expansion protocol was also successfully applied to 3-ethynylcycloalkanones, giving rise to the corresponding ring-expanded cyclic allenes (cf. Scheme,13). [source] A general method to prepare monodentate phosphane ligands with mixed substituentsHETEROATOM CHEMISTRY, Issue 7 2009Jennifer E. Phelps Treatment of (2,2,-biphenylylene)- phosphorchloridite ester [(C12H8O2)PCl] (1) with C2F5Li yields (C12H8O2)PC2F52; treatment of 1 with Grignard reagents yields compounds of the type (C12H8O2)PR (R = iPr, 5; Et 6). In both cases, the 1,3-dioxepine ring formed when 2,2,-biphenol reacts with PCl3 to form 1 serves as a protecting group at the phosphorus atom; the ring allows the stepwise introduction of one substituent and prevents undesirable product mixtures associated with multiple substitutions at the phosphorus. Additional treatment of compounds 2, 5, and 6 with Grignard, alkyl-, or aryllithium reagents results in the formation of unsymmetrically substituted phosphanes. The use of (2,2,-biphenylylene)phosphorchloridite ester as a starting material for the preparation of electroneutral phosphanes of the type (Rf)PR2 and electron-poor phosphanes of the type (Rf)2PR is described. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 20:393,397, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20563 [source] Studies on organophosphorus compounds: Synthesis and reactions of [1,2,4,3]triaza-phospholo[4,5- a]quinoxaline derivativeHETEROATOM CHEMISTRY, Issue 5 2008Hassan M. Moustafa 2,4-Bis-(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane-2,4-disulfide (Lawesson's reagent) (1) reacted with 2-hydrazino-3-methyl-quinoxaline (2) to give [1,2,4,3]-triazaphospholo[4,5- a]quinoxaline derivative 3. The Mannich reaction using different amines on compound 3 gave Mannich bases 4a,d. Also, compound 3 reacted with formaldehyde to give the corresponding 2-hydroxymethyl derivative 5, which upon reaction with thionyl chloride gave the corresponding chloromethyl derivative 6. Treatment of compound 6 with some thiols yielded the corresponding sulfides 7a,d. Acylation of compound 3 gave acylated compounds 8a,b. Compound 9, which was prepared through the reaction of compound 3 with ethyl cyanoacetate, was investigated as a starting material for the synthesis of some new heterocyclic systems 10,13. Also, reaction of compound 9 with carbon disulfide and 2 equivalents of methyl iodide in a one-pot reaction yielded the corresponding ketene-S,S-acetal 14, which in turn reacted with bidentates to give some new heterocycles 15,17. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:520,529, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20473 [source] | ||||||||||||||||||||||||||||||||||||||||