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Moderate Yields (moderate + yield)
Selected AbstractsA Trinuclear Aqua Cyano-Bridged Ruthenium Complex [{(,5 -C5H5)(PPh3)2Ru(,-CN)}2RuCl2(PPh3)(H2O)]PF6: Synthesis, Characterization and Crystal StructureEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2007Viatcheslav Vertlib Abstract The organometallic trinuclear aqua cyano-bridged complex [{(,5 -C5H5)(PPh3)2Ru(,-CN)}2RuCl2(PPh3)(H2O)]PF6 (1), in which the fragment [RuCl2(PPh3)(H2O)] acts as a bridge and an acceptor group between the two terminal cyclopentadienyl ruthenium cyano moieties, was isolated in moderate yield from the reaction of [(,5 -C5H5)(PPh3)2RuCN] with [RuCl2(PPh3)3] in THF. To the best of our knowledge, compound 1 is one of the few examples of a trinuclear array of ruthenium fragments bridged by the nitrogen atom of the,C,N, group (Ru,C,N,Ru,,N,C,Ru) with a Ru-coordinated water molecule. The new aqua complex was structurally characterized by FTIR, 1H, 13C, and 31P NMR spectroscopy, mass spectrometry, elemental analysis, single-crystal X-ray diffraction, and cyclic voltammetry. The title complex crystallizes in a triclinic unit cell a = 17.3477(6) Å, b = 17.8551(5) Å, c = 18.2460(7) Å, , = 95.693(2)°, , = 111.648(2)°, and , = 97.839(2)° in the space group P with Z = 2.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Reactions of GaCp* with a Hemilabile Derivative of Rh6(CO)16 , Synthesis and Structural Characterization of Two Novel Heterometallic Clusters: Rh6(CO)13(,,,3 -Ph2PC2H3)(,3 -GaCp*) and Rh6(CO)13(,1 -Ph2PC2H3)(,3 -GaCp*)2EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2007Elena V. Grachova Abstract The reaction of Rh6(CO)14(Ph2PCH=CH2) with a twofold excess of GaCp* (Cp* = C5Me5) affords two novel heterometallic clusters Rh6(CO)13(,,,3 -Ph2PC2H3)(,3 -GaCp*) (1) and Rh6(CO)13(,1 -Ph2PC2H3)(,3 -GaCp*)2 (2) in a moderate yield. The hemilabile behavior of coordinated diphenylvinylphosphane in the starting cluster allows the easy insertion of GaCp* into the cluster coordination sphere, which eventually gives the cluster 1 with face-bridging coordination of the gallium fragment and the phosphane ligand recoordinated in an edge-bridging position. The further substitution of the vinyl function in 1 for the second GaCp* ligand affords cluster 2, where recoordination of the double bond is blocked by steric hindrance from adjacent GaCp* fragments. Both clusters were structurally characterized by X-ray crystallography in the solid state and by IR and NMR spectroscopy in solution. Hemilability of diphenylvinylphosphane in 1 was independently confirmed by the cluster reaction with CO, which gives the Rh6(CO)14(,1 -Ph2PC2H3)(GaCp*) adduct (3) with the phosphane ligand only coordinated through the phosphorus atom. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] A Ruthenium(II)-Complexed Rotaxane Whose Ring Incorporates a 6,6,-Diphenyl-2,2,-bipyridine: Synthesis and Light-Driven MotionsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2005Jean-Paul Collin Abstract By incorporating a 6,6'-diphenyl-2,2'-bipyridine (dpbipy) fragment in a ring, endo coordination of a ruthenium(II) center is performed selectively and almost quantitatively. The threaded system, containing a helical fragment, could be fully characterized. When the terminal functions of the rod-shaped helical complex threaded through the macrocycle are phenol groups, the complete rotaxane is prepared by the classical Williamson stoppering reaction in moderate yield. Light-induced motions of the unstoppered system (pseudorotaxane) and the real rotaxane have been studied. Under visible light irradiation, quantitative decoordination of the dpbipy-containing ring is observed, leading to the separate fragments (ring and helical thread) or to a new rotaxane (uncoordinated ring threaded by the dumbbell). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Synthesis of herbicidal 3-substituted-4(3H)-pyrimidinones under high pressureJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 3 2001Artur Jezewski The reaction of an N -monosubstituted amidine with a ,-ketoester to afford a pyrimidinone is sluggish at best under normal conditions. We now report that this reaction can be effected in moderate yield under high pressure. Thus, 2,6-dichloro-4-pyridyl-(N -prop-2-ynyl)carboxamidine (4b) was reacted with three ,-substituted-,-ketoesters (2b-d) at 10,16 kbar to afford herbicidal 2-(2,6-dichloro-4-pyridyl)-3-(prop-2-ynyl)-4(3H)-pyrimidinones 5b and 5c in 15 - 43% yield. This result expands the scope of reactions promoted by application of high pressure. [source] Convenient substitution of hydroxypyridines with trifluoroacetaldehyde ethyl hemiacetalJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 1 2001Yuefa Gong Thermal substitution of 4-hydroxypyridine 1 with trifluoroacetaldehyde ethyl hemiacetal (TFAE) leads to a moderate yield of 3-(1-hydroxy-2,2,2-trifluoroethyl)-4-hydroxypyridine 7 in the presence of a catalytic amount of anhydrous potassium carbonate. Under similar conditions, several ,-trifluoromethyl hydroxy-pyridinemethanols 8,15 are easily prepared from 2- or 3-hydroxypyridines 2,6. [source] Selective polymerization of functional monomers with Novozym 435JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2007Martijn A. J. Veld Abstract Two novel monomers, ambrettolide epoxide and isopropyl aleuriteate, encompassing functional groups, were obtained in a single step from commercially available materials. Novozym 435 catalyzed ring opening polymerization of ambrettolide epoxide furnished a polymer of Mn = 9.7 kg/mol and PDI = 1.9 while the epoxide groups remained unaffected during the polymerization. Selective polymerization of the primary hydroxyl groups of isopropyl aleuriteate using Novozym 435 was feasible and a polymer with moderate molecular weight (Mn = 5.6 kg/mol, PDI = 3.2) was isolated in moderate yield (43%). Subsequently, copolymerization of isopropyl aleuriteate with ,-CL in different ratios was performed, resulting in soluble, hydroxy functional polymers with good molecular weights (Mn = 10.4,27.2 kg/mol) in good yield (71,78%). The secondary hydroxy groups in the polymer reacted easily with hexyl isocyanate, showing the potential of isopropyl aleuriteate as a comonomer for the synthesis of functional polyesters. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5968,5978, 2007 [source] Synthesis and Cyclohexene Oxide/Carbon Dioxide Copolymerizations of Zinc Acetate Complexes Bearing Bidentate Pyridine-Alkoxide LigandsMACROMOLECULAR RAPID COMMUNICATIONS, Issue 8 2004Il Kim Abstract Summary: The reaction of 2-lithio-6-methylpyridine or 2-lithiopyridine and the appropriate diaryl ketone followed by hydrolysis yields 6-Me-pyCAr2OH pyridine alcohols or pyCAr2OH pyridine alcohols. The reactions of zinc acetate with 1 equiv. of the lithiated products of the ligands proceed rapidly to afford LiOAc salt and mono-ligand complexes (6-Me-pyCAr2O)Zn(OAc) and (pyCAr2O)Zn(OAc), respectively, in high yield. The copolymerizations of carbon dioxide with cyclohexene oxide were investigated. The (6-Me-pyCAr2O)Zn(OAc) showed moderate yield and CO2 incorporation. The [6-Me-pyC(4-Cl-C6H4)2O]Zn(OAc) complex gave large polymers with high proportions of carbonate linkage (>60%) and narrow polydispersity, indicating single active sites. The monoligated Zn complexes synthesized and used here as catalysts for the copolymerization of cyclohexene oxide and carbon dioxide. [source] Six-membered cyclic sulfites derived from glucofuranose and 1,2,4-butanetriol,CHIRALITY, Issue 9 2001Katarzyna Borsuk Abstract Six-membered cyclic sulfites derived from glucofuranose derivatives 5, 6 and from 1- O-tert -butyldimethylsilil-1,2,4-butanetriol 12 were synthesized and separated into pure diastereomers which were in turn subjected to the sequence of reactions leading to the introduction of the terminal vinyl ether fragment. Reactivity and applicability of cyclic sulfites as intermediates in [2+2]cycloaddition of chlorosulfonyl isocyanate (CSI) to vinyl ethers were studied. The cycloaddition to vinyl ethers 19 and 20 proceeded in low yield and low asymmetric induction, in the case of the former, and moderate yield and pronounced asymmetric induction, in the case of the latter. The 1H-NMR spectra of sulfites 13,16 reveal a preference of the sulfite oxygen atom for the axial position. Thus, well-defined conformation in solution for compounds 13 and 15 and a mixture of the two possible chair forms for sulfites 14 and 16 could be assigned. The stretching frequency of the S,O bond in stable conformation with an axial sulfite oxygen occurs in the range 1,160,1,210 cm,1, whereas conformationally mobile sulfites exhibit corresponding absorption above 1,220 cm,1. The absolute configuration assignments of sulfites 7, 8, 15, 16 and 25,28 were done empirically based on the combined analysis of the NMR, IR, X-ray, and dichroic data. It was demonstrated that the sign of the Cotton effect around 194 nm correlated with the absolute stereochemistry at the sulfur atom in a sulfite chromophore. Chirality 13:533,540, 2001. © 2001 Wiley-Liss, Inc. 2001. [source] Asymmetric Aza-Morita,Baylis,Hillman Reactions of Alkyl Vinyl Ketones with N -Protected Imines or In Situ Generated N -Protected IminesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 21 2010Xiao-Yang Guan Abstract DABCO-catalyzed aza-MBH reactions of N -Boc imines with MVK and EVK have been thoroughly investigated in the paper. The asymmetric version of this aza-MBH reaction was also systematically investigated by using a chiral amine or a chiral phosphane catalyst. It was found that most of the N -protected imines are suitable substrates under the mild reaction conditions and are able to give the corresponding adducts in moderate yields with high ee values. The TQO- or LB1-catalyzed aza-MBH reactions of N -protected ,-amidoalkyl phenyl sulfones or ,-amidoalkyl p -tolyl sulfones with MVK could be well conducted, which provides a facile and direct route to obtain highly enantioselective aza-MBH adducts. The Boc protecting group of the aza-MBH product could be easily removed under acidic conditions to give the corresponding ,-methylene-,-amino ketone or ,-methylene-,-amino alcohol derivatives in good yields. [source] Facile Construction of Spirocyclopropanated Bi-, Tri- and Tetracyclic Skeletons by Novel Cascades Involving Intra- and Intermolecular Heck Reactions of 2-Bromo-1,6-enynes and BicyclopropylideneEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 3 2005Michael Schelper Abstract Acyclic 2-bromo-1,6-enynes 5 -R, 9 -R and 11 -R with bulky substituents at the acetylenic terminus were co-cyclized with the highly strained bicyclopropylidene (12) under palladium catalysis at 80 °C to give the cross-conjugated tetraenes 13 -R, 18 -R and 19 -R in moderate-to-good yields (34,71%). Only the co-cyclization of 5 -Ph gave rise to an additional product, which was identified as the 11-membered ring 20. At elevated temperatures (120,140 °C) the initially formed tetraenes underwent 6,-electrocyclization to give spiro[cyclopropane-1,4,-bicylo[4.3.0]-1(6),2-dienes] 21 -R, 22 -R and 23 -R. This novel class of spirocyclopropanated oligocycles is also accessible by a one-pot protocol. The highest yields for both the tetraenes and bicyclo[4.3.0]nonadiene and its heteroanalogues were obtained with bulky substituents at the alkyne terminus of the precursors. Heteroatom-containing precursors 9 -R and 11 -R gave lower yields than their all-carbon analogues 5 -R. The acyclic 2-bromo-1,8-dien-6-ynes 28a,b,c upon palladium-catalyzed co-cyclization with bicyclopropylidene (12) at 110 °C gave spirocyclopropanated tricycles 31a,b and 32, respectively, in moderate yields (14, 31 and 32%). These products were formed by two consecutive 6,-electrocyclizations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] One-Pot Synthesis of Tetraalkyl Benzene-1,2,3,5-tetracarboxylates from a Four-Component Reaction of Alkyl Propiolates and Alkyl 2-Nitroethanoates Promoted by Ph3PHELVETICA CHIMICA ACTA, Issue 12 2006Issa Yavari Abstract Alkyl 2-nitroethanoates react with alkyl propiolates in the presence of triphenylphosphine (Ph3P) in a mechanistically unprecedented reaction to afford tetraalkyl benzene-1,2,3,5-tetracarboxylates in moderate yields (36,42%). [source] Internal Nucleophilic Termination in Acid-Mediated Polyene Cyclizations Part 4,HELVETICA CHIMICA ACTA, Issue 12 2005Synthetic Access to Tetracyclic Didehydro, Tetradehydro Analogues of (±)- Ambrox® Treatment of the unsaturated bicyclic homoallylic alcohols (E)- and (Z)- 5 and (Z)- and (E)- 10 and allenic alcohol 16 with an excess of ClSO3H in 2-nitropropane or CH2Cl2 at ,,80° afforded, in moderate yields (ca. 30,70%), diastereoisomer mixtures of racemic tetracyclic ethers 12a,c (Table,1) and 17a,b (Table,2), respectively. These kinetically controlled stereospecific transformations are believed to proceed via concerted or nonconcerted pathways (see Schemes,4 and 6) and the results are fully consistent with our earlier work. Representing novel didehydro bridged analogues of known, olfactively active labdane tricyclic ethers, the organoleptic properties of 12a,c and 17a,b are briefly described, especially those of 12c which, in the context of structure,activity studies, is a racemic didehydro analogue of the known ambergris odorant Ambrox®. [source] A Novel Coupling 1,3-Dipolar Cycloaddition Sequence as a Three-Component Approach to Highly Fluorescent IndolizinesHELVETICA CHIMICA ACTA, Issue 7 2005Alexandru Indolizines 4 and biindolizines 6 can be synthesized in moderate yields in a consecutive one-pot three-component process by a coupling/1,3-dipolar cycloaddition sequence of a (hetero)arenecarbonyl chloride 1, a terminal alkyne 2, and a suitable 1-(2-oxoethyl) pyridinium bromide 3 or 5, respectively (Schemes,1 and 2). After the Sonogashira coupling, a [2+3] cycloaddition of the in situ formed pyridinium ylide, an allyl-type 1,3-dipole, furnishes a cycloadduct that is instantaneously oxidatively aromatized to give the highly fluorescent indolizine derivatives that were unambiguously characterized by an X-ray-structure analysis of compound 4d (Fig.,1). Additionally, fluorescence studies with pyridinyl-substituted representatives reveal not only that indolizines and biindolizines are highly interesting fluorescence dyes but that their fluorescence color can also be reversibly switched upon altering the pH of the medium. [source] Reaction of diethyl thiocyanatomethylphosphonate with aldehydes as a route to diethyl Z -1-alkenylphosphonatesHETEROATOM CHEMISTRY, Issue 7 2007Roman B, aszczyk Diastereoselective synthesis of diethyl Z-1-alkenylphosphonates from easily available diethyl thiocyanatomethylphosphonate and aromatic aldehydes has been developed. Olefination of the aldehydes occurs under mild conditions and affords the title compounds with moderate yields. A plausible mechanism of the above-mentioned reaction is also discussed. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:732,739, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20371 [source] Two-step syntheses of 3-methyl and 3-phenyl-1,2,4-benzotriazinesHETEROATOM CHEMISTRY, Issue 2 2006Mohamed Khodja 3-Methyl-1,2,4-benzotriazine and some of its derivatives were prepared in moderate yields (50,70%) via a reductive cyclization by a PtO2 -catalyzed hydrogenation of the corresponding 2-nitrophenylhydrazones of the pyruvic acid. The latter compounds were obtained in yields higher than 90% by reacting 2-nitrophenylhydrazines with sodium pyruvate salt. Three 3-phenyl-1,2,4-benzotriazine compounds were also produced via a reductive cyclization by a Pt/C-catalyzed hydrogenation of their corresponding 2-nitrophenylhydrazono-ethers in high yields (>70%). © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:166,172, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20200 [source] Efficient and Highly Chemoselective Direct Reductive Amination of Aldehydes using the System Silane/Oxorhenium ComplexesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2010Sara C. A. Sousa Abstract This work reports a novel method for direct reductive amination of aldehydes with silanes catalyzed by several high-valent oxorhenium(V) and oxorhenium(VII) complexes. The catalytic system PhSiH3/ReIO2(PPh3)2 (2.5,mol%) was very efficient for the synthesis of secondary amines and highly chemoselective, tolerating a wide range of functional groups such as NO2, CF3, SO2R, CO2R, F, Cl, Br, I, CN, OH, OCH3, SCH3, NCOR, and double bonds. This novel method was also employed in the synthesis of tertiary amines with moderate yields. [source] Metalloporphyrin/Iodine(III)-Cocatalyzed Oxygenation of Aromatic HydrocarbonsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2010Akira Yoshimura Abstract Hypervalent iodine species have a pronounced catalytic effect on the metalloporphyrin-mediated oxygenations of aromatic hydrocarbons. In particular, the oxidation of anthracene to anthraquinone with Oxone readily occurs at room temperature in aqueous acetonitrile in the presence of 5,20,mol% of iodobenzene and 5,mol% of a water-soluble iron(III)-porphyrin complex. 2- tert -Butylanthracene and phenanthrene also can be oxygenated under similar conditions in the presence of 50,mol% of iodobenzene. The oxidation of styrene in the presence of 20,mol% of iodobenzene leads to a mixture of products of epoxidation and cleavage of the double bond. Partially hydrogenated aromatic hydrocarbons (e.g., 9,10-dihydroanthracene, 1,2,3,4-tetrahydronaphthalene, and 2,3-dihydro-1H -indene) afford under these conditions products of oxidation at the benzylic position in moderate yields. The proposed mechanism for these catalytic oxidations includes two catalytic redox cycles: 1) initial oxidation of iodobenzene with Oxone producing the hydroxy(phenyl)iodonium ion and hydrated iodosylbenzene, and 2) the oxidation of iron(III)-porphyrin to the oxoiron(IV)-porphyrin cation-radical complex by the intermediate iodine(III) species. The oxoiron(IV)-porphyrin cation-radical complex acts as the actual oxygenating agent toward aromatic hydrocarbons. [source] Combinatorial Design of Copper-Based Mixed Nanoclusters: New Catalysts for Suzuki Cross-CouplingADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 8 2003Mehul Abstract Quantum dots (2,5,nm) of copper and copper/palladium mixtures are found to be good catalysts for Suzuki cross-coupling. The catalysts are applicable to a wide range of iodo- and bromoaryl substrates, and give moderate yields using chloroaryl substrates. Cluster activity and stability is found to depend strongly on the preparation method and the reaction conditions. The mechanism of cluster deactivation and the sensitivity of the cluster-catalysed reaction to substituent effects are studied and discussed. [source] Regio- and stereoselective synthesis of isoxazolidine derivatives by asymmetric 1,3-dipolar cycloaddition reaction of chiral nitrones with 1-propene-1,3-sultoneJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 4 2008Hong-Kui Zhang Asymmetric 1,3-dipolar cycloadditions of chiral nitrones to 1-propene-1,3-sultone (1) were investigated. Chiral nitrones 6a-e reacted with sultone 1 in toluene at 90 °C for 24-36 h to give the corresponding isoxazolidines in moderate yields with high regioselectivities and stereoselectivities. The diastereoselectivity of this reaction varied with the choice of dipolarophile and the steric demands of nitrones. When sultone 1 was allowed to react chiral nitrone 6e, a much better diastereoselectivity of up to 5.1:1 was observed. [source] Synthetic analogs of dioncophylline and michellamines by stille couplingJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2006Abdel-Sattar S. Hamad Elgazwy Dioncophielline and Michellamine Analogs S-5, R-5, S-7, R-7, S,S-8, R,R-8 and R,S-8 were synthesized by using Stille coupling condition (Pd°-mediated cross coupling) proceeds in low yield when using stannanes 1 or 2 with tetrahydroisoquinolinyl bromide 3. The addition of tetrahydroisoquinolinyl iodide 4 instead of 3 significantly improves the efficiency of the coupling and providing a variety of Dioncophielline and Michellamine analogs in moderate yields. [source] Synthesis of amidocrownophanes with 27- and 28-membered rings and their molecular recognition toward urea and its derivativesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 4 2005Kazuhisha Hiratani Novel crownophanes with 27- and 28-membered rings having two hydroxyl groups, two amide groups, and aromatic moieties such as naphthalene, pyridine, and phenyl rings were successfully synthesized by a one-step reaction from the corresponding macrocyclic polyethers via "tandem Claisen rearrengement" in moderate yields. They can solubilize urea and its derivatives into chloroform solution, while the corresponding macrocyclic polyethers do not solubilize them. According to NMR studies, crownophanes 1 and 2 interact with urea and its derivatives forming 1:1 complexes. [source] Syntheses and properties of dithia-tetrahomodiaza-calix[4]arenes bridged by cystine unitJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 3 2003Kazuaki Ito Dithia-tetrahomodiaza-calix[4]arenes were synthesized by the cyclization reactions of bis(3-(chloro-methyl)-2-hydroxyphenyl)sulfide with cystine peptides in moderate yields. Conformational analysis of the macrocycles by using nmr spectroscopy reveled that the cyclophanes adopt a cone-like form as a preferable conformation and the cystine bridge moiety is incorporated in the cavity. The calixarene analogs can extract transion metals such as Zn2+ and Cu2+ ions from an aqueous phase into chloroform. [source] A facile synthesis of 3-Substituted 5-Oxo-1,2,4-thiadiazoles from amidoximes,JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 6 2000Yasuhisa Kohara The reaction of amidoximes 1 with 1,1,-thiocarbonyldiimidazole (TCDI) followed by treatment with silica gel or boron trifluoride diethyl etherate (BF3·OEt2) provided 3-substituted 4,5-dihydro-5-oxo-1,2,4-thiadiazoles 2 in moderate yields. The Lewis acids are considered to promote the rearrangement of the thioxocarbamate intermediates 5 to the thiol carbarn ate intermediates 7, which cyclize to afford 4,5-dihydro-5-oxo-1,2,4-thiadiazoles 2. [source] A new practical tritium labelling procedure using sodium borotritide and tetrakis(triphenylphosphine)palladium(0)JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 14 2001Tohru Nagasaki Abstract A simple, mild and versatile new tritium (3H) labelling method on a micro scale using sodium borotritide (NaB3H4) and a transition,metal complex catalyst is described. 3H-labelled compounds were prepared effectively by 3H hydrogenolysis of appendant functional groups in target compounds. The appendant functional group such as bromo, iodo or sulfonate in various target compounds can be replaced by tritium (3H) in moderate yields. The new method was established by optimization of the reaction conditions and examination of its applicability using four types of model substrates in tracer runs. Then, various drug candidates and ligands for drug discovery were labelled with tritium on a micro scale. The specific radioactivity of the 3H-labelled compounds used for the studies on receptor binding ranged from 12 to 20 Ci/mmol. Copyright © 2001 John Wiley & Sons, Ltd. [source] Solvent-free synthesis of pseudopolyrotaxane and polyrotaxane: Efficient threading complexation of a cyclodextrin wheel and a linear polymer axle to yield pseudopolyrotaxane and its fixation to polyrotaxane by the direct grinding of a solid mixtureJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2007Runtao Liu Pseudopolyrotaxane was obtained through the grinding of a mixture of O -trimethyl-,-cyclodextrin and polytetrahydrofuran in a mortar by solvent-free synthesis, and it was fixed to stable polyrotaxane by a successive end-capping reaction with a bulky isocyanate by solid-state grinding in a mortar. Higher molecular weight polytetrahydrofurans (Mn > 1000) successfully produced corresponding polyrotaxanes in moderate yields and with moderate coverage ratios. O -Trimethyl-,-cyclodextrin and poly(ethylene glycol) also formed corresponding pseudopolyrotaxanes and polyrotaxanes by the grinding method. [source] Synthesis of poly(phenylsilsesquioxane) having organostannyl groupsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2001Yasutaka Matsubara Abstract Poly(phenylsilsesquioxane) (PSQ) having tributylstannyl groups (TBPSQ) was prepared from phenyltrimethoxysilane and bis(tributyltin) oxide [(Bu3Sn)2O] under basic conditions. The procedure, using a catalytic amount of basic reagent such as triethylamine, sodium hydroxide, or aqueous ammonia, afforded yields of TBPSQ based on Si in the range of 12,45% at a number-average molecular weight precipitated from ethanol of about 3500. In the other procedure, starting from PSQ with (Bu3Sn)2O, the incorporation of tributylstannyl groups into PSQ proceeded effectively in the presence of an acid catalyst such as methanesulfonic acid or sulfuric acid, giving TBPSQ in moderate yields of greater than 52%. Dibutyltin oxide, a bifunctional organotin compound, was also used, affording dibutylstannylated poly(phenylsilsesquioxane) (DBPSQ) without crosslinking. The highest ratio of Si and Sn contained in TBPSQ or DBPSQ, prepared under acidic conditions, was Si/Sn = 7/1. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2125,2133, 2001 [source] Unexpected regioselectivity in the palladium-catalyzed reaction of silacyclobutanes with aryl iodidesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 8 2001Yoshifumi Tanaka Abstract The reaction of aryl iodides with 1,1-diphenyl-silacyclobutane in the presence of a catalytic amount of Pd(PPh3)4 affords unexpected ring-opening adducts, 1- and 2-propenyl(triaryl)-silanes, in good yields. On the other hand, the PdCl2(PhCN)2 -catalyzed reaction of 1,1-diphenylsilacyclobutanes with aryl halides gives unexpected products, triarylsilanols, after hydrolysis in moderate yields. The catalysis involves the reaction of aryl,palladium intermediates with silacyclobutanes along with regioselective aryl,silicon bond formation. Copyright © 2001 John Wiley & Sons, Ltd. [source] [PdCl2(MeCN)2]-Catalyzed Highly Regio- and Stereoselective Allylation of Electron-Rich Arenes with 2,3-AllenoatesCHEMISTRY - A EUROPEAN JOURNAL, Issue 13 2010Zhao Fang Selective allylation: Several electron-donating arenes such as 1,3,5-trimethoxybenzene, anisole, and phenol underwent palladium-catalyzed selective allylation in TFA/dimethylacetamide (DMA) under mild conditions with 2,3-allenoates (see scheme). The reaction afforded substituted 4,4-diarylbut-2(E)-enoates in moderate yields with high regio- and stereoselectivity. [source] A Gold(I)-Catalyzed Intramolecular Reaction of Propargylic/Homopropargylic Alcohols with OxiraneCHEMISTRY - A EUROPEAN JOURNAL, Issue 23 2008Lun-Zhi Dai Abstract The gold(I)-catalyzed cycloisomerization of epoxy alkynes in the presence of a nucleophile is an efficient protocol to provide ketal skeletons with high stereoselectivity. An intramolecular reaction of propargylic/homopropargylic alcohols with oxirane to produce ketal/spiroketals in moderate yields under mild conditions has been reported. Moreover, the mechanism of this kind of reaction has been discussed on the basis of a series of control and 18O tracer experiments. [source] Synthesis of ,-Methoxyacrylate Natural Products Based on Box-PdII -Catalyzed Intermolecular Methoxycarbonylation of AlkynolesCHEMISTRY - AN ASIAN JOURNAL, Issue 10 2010Satoshi Motodate Abstract Bis(oxazoline)-palladium(II) catalyzed carbonylation of homopropargyl alcohols afforded acyclic methoxyacrylate 2 and 6-membered lactone 3,a,k in good combined yield. In the case of propargyl alcohols, 5-membered lactones 3,p, 3,q, 16 were obtained in moderate yields. The one-pot synthesis of kawa lactones 3,a, 3,r, 3,s and formal synthesis of dihydroxycystothiazole,A and dihydroxycystothiazole,C are presented. To elucidate the stereochemistry of (+)-annularin G and (,)-annularin H, the first asymmetric syntheses of these natural products were achieved. [source] | ||||||||||||||||||||||||||||