Excellent Yields (excellent + yield)

Distribution by Scientific Domains
Distribution within Chemistry


Selected Abstracts


ChemInform Abstract: Rapid, Efficient, and Room Temperature Synthesis of Nitrones in Excellent Yields over MgO under Solvent-Free Conditions.

CHEMINFORM, Issue 33 2009
Hassan Valizadeh
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]


A Convenient and Efficient Rhenium-Catalyzed Hydrosilylation of Ketones and Aldehydes

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009
Hailin Dong
Abstract The easily available rhenium(I) complex [Re(CH3CN)3Br2(NO)] catalyzes the homogeneous hydrosilylation of a great variety of organic carbonyl compounds (ketones and aldehydes). The reaction is quite sensitive to the solvent applied. Chlorobenzene was found to be superior over all the other solvents used. Various aliphatic and aromatic silanes were tested. Excellent yields were achieved at 85,C in chlorobenzene using triethylsilane, the reaction affording TOF values of up to 495,h,1. A possible reaction mechanism for the hydrosilylation is presented. [source]


The First Thiadiazolidine 1-Oxide System for Phosphine-Free Palladium-Mediated Catalysis

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009
Benjamin
Abstract We herein report a highly active catalyst system using for the first time a thiadiazolidine 1-oxide as a ligand for palladium in the Mizoroki,Heck reaction. Excellent yields of stilbenes derived from aryl iodides and bromides have been achieved using as little as 0.00002,mol% catalyst. The ligand/palladium system can be stored as a stock solution open to air at room temperature with no observable loss of activity for a period of several weeks/months. [source]


A Catalytic Enantioselective Imino-Reformatsky Reaction

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 15 2006
Pier Giorgio Cozzi
Abstract The admission of air in the reaction mixture of imine, ethyl iodoacetate and dimethylzinc, in the presence of 20,30 mol,% of inexpensive and commercially available N -methylephedrine as the chiral ligand, promoted the Reformatsky reaction, without the need for other metals or catalysts. Excellent yields (up to 92,%) and enantioselectivities (83,94,%) were obtained for the tested substrates. The reaction shows a broad scope, and all the imines are prepared in situ, using Me2Zn as the dehydrating agent. [source]


Immobilization of HX: [Hmim]X as halogenating agent, recyclable catalyst and medium for conversion of alcohols to alkyl halides

CHINESE JOURNAL OF CHEMISTRY, Issue 7 2004
Hai-Hong Wu
Abstract HX is immobilized by reaction of halogen acid with methylimidazole, and the formed ionic liquid [Hmim]X was used as halogenating agent, catalyst as well as medium for conversion of alcohols to alkyl halides. Excellent yields were obtained. The halides produced could be easily separated from the reaction mixture via simple decantation, and the ionic liquid [Hmim]X could be regenerated conveniently by adding equivalent of halogen acids followed by removal of water. [source]


Allylic Amination of Internal Alkynes with Aromatic and Aliphatic Amines Using Polymer-Supported Triphenylphosphane,Palladium Complex as a Heterogeneous and Recyclable Catalyst

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 26 2010
Yogesh S. Wagh
Abstract A facile and novel protocol for the allylic amination of internal alkynes with amines by using a polymer-supported triphenylphosphane,palladium complex [PS,TPP,Pd] as a highly active heterogeneous reusable catalyst was developed. The catalyst exhibited remarkable activity and is reusable over five consecutive cycles. The protocol was applicable for a variety of hindered and functionalized aromatic/aliphatic amines and afforded the desired allylic products in good to excellent yield. [source]


Synthesis of Polysubstituted 3-Iodopyrans by Electrophilic Cyclization

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 14 2009
Yong-Xin Xie
Abstract A variety of polysubstituted 3-iodopyrans were readily prepared in good to excellent yield under mild reaction conditions by the reaction of alkynyl carboxamides with ICl, I2, and NIS. The products obtained from this process are versatile materials that can be used to construct other complex functionalized pyran structures of importance. The occurrence of the pyranyl group in both natural products and pharmaceuticals confers important value to this study. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


Click Chemistry Inspired Synthesis of Novel Ferrocenyl-Substituted Amino Acids or Peptides

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 13 2009
V. Sai Sudhir
Abstract This work reports on the synthesis of a wide range of ferrocenyl-substituted amino acids and peptides in excellent yield. Conjugation is established via copper-catalyzed 1,3-dipolar cycloaddition. Two complementary strategies were employed for conjugation, one involving cycloaddition of amino acid derived azides with ethynyl ferrocene 1 and the other involves cycloaddition between amino acid derived alkynes with ferrocene-derived azides 2 and 3. Labeling of amino acids at multiple sites with ferrocene is discussed. A new route to 1,1,-unsymmetrically substituted ferrocene conjugates is reported. A novel ferrocenophane 19 is accessed via bimolecular condensation of amino acid derived bis-alkyne 9b with the azide 2. The electrochemical behavior of some selected ferrocene conjugates has been studied by cyclic voltammetry.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


Selective Palladium-Catalysed ipso Arylation of ,,,-Disubstituted Benzo[b]thien-2-ylmethanols with Aryl Bromides using PCy3 as Ligand

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 8 2007
A. Beatrix Br
Abstract ,,,-Diphenylbenzo[b]thien-2-ylmethanol was treated with a series of aryl bromides in the presence of palladium(II) acetate and tricyclohexylphosphane to give the appropriate 2-aryl-benzo[b]thiophenes in good to excellent yield with concomitant formation of benzophenone. The reaction wassuccessfully extended to ,,,-diphenylbenzo[b]thien-3-ylmethanol, although in certain cases the transformation was biased by concurrent ortho arylation. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]


Palladium-Catalyzed Preparation of Propargylic or Allenylic Sulfides from Propargyl Halides or Mesylate and Thiols

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 3 2004
Ken Tsutsumi
Abstract In the presence of a catalytic amount of Pd0 -dppe complex [dppe: 1,2-bis(diphenylphosphanyl)ethane], generated in situ from [Pd2(dba)3CHCl3] and dppe, propargylic bromide 1a reacted with an equimolar amount of propanethiol at 60 C in DMF to afford propargylic sulfide 2 in an excellent yield. The reaction occurs readily when carried out in the presence of the weak base triethylamine. The choice of both the phosphane, which is employed as the palladium atom's ligand, and the solvent have a remarkable effect on this reaction. We found that the optimum conditions for the reaction are those using a bidentate phosphane ligand (dppe) in a polar solvent (DMF). Compound 1a reacted smoothly with both aromatic (PhSH) and secondary thiols (CySH) in high yields. The reactions with thiols bearing functional groups (OH or Cl) proceeded selectively in good to moderate yields. Primary chlorides 1b,e were readily converted into their corresponding propargylic sulfides 7,10 in high yields. The Pd0 -dppe catalyst was ineffective in the reaction of the bromide 1g bearing a tBu group at the propargylic position, but the reaction of the corresponding mesylate 1h using the Pd0 -DIOP catalyst [DIOP = O -isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphanyl)butane] at 100 C afforded the product 11 in good yield. Allenylic sulfides were obtained from 1g,i. We suggest that a cationic ,3 -type complex may be a more reactive intermediate in this catalytic reaction than neutral ,1 - or ,3 -allenyl/propargylpalladium complexes. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]


Syntheses, spectral property, and antimicrobial activities of 6-,-amino dibenzo [d,f][1,3,2]dioxaphosphepin 6-oxides

HETEROATOM CHEMISTRY, Issue 1 2007
M. Kasthuraiah
Diethyl ,-aminophosphonates (4) were prepared in excellent yield from three-component reaction of aldehydes (1), amines (2), and triethylphosphite (3) under solvent-free conditions in the presence of ceric ammonium nitrate (CAN) and were reacted with 2,2,-dihydroxybiphenyl (5) using p -toluene sulfonic acid monohydrate (PTSA) as a catalyst to obtain 6-,-aminodibenzo[d f][1,3,2]dioxaphosphepin 6-oxides (6) in good yield. It is a first report on the cyclizations of 4 with 5. An antimicrobial activity of numbers of 6 is evaluated. 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:2,8, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20244 [source]


A Homogeneous Catalyst for Reduction of Optically Active Esters to the Corresponding Chiral Alcohols without Loss of Optical Purities

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1 2010
Wataru Kuriyama
Abstract A ruthenium complex was found to catalyze the hydrogen reduction of esters under mild and neutral conditions. A variety of optically active esters can be reduced to the corresponding alcohols in excellent yield without loss of their optical purity or causing undesirable side reactions. Hydrogen reduction needs such simple operations , reaction, concentration, and purification , that the violent quench step and extraction step, which accompany conventional sodium borohydride or lithium aluminum hydride reduction, can be omitted. [source]


Back to Natural Cinchona Alkaloids: Highly Enantioselective Michael Addition of Malononitrile to Enones

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009
Alessio Russo
Abstract An efficient and convenient highly enantioselective Michael addition of malononitrile to enones has been developed by using quinine as the organocatalyst. The adducts were isolated in excellent yield and high asymmetric induction (up to 95% ee). An easy route to difficultly accessible ester derivatives has been also disclosed. [source]


Copper-Catalyzed N -Alkylation of Sulfonamides with Benzylic Alcohols: Catalysis and Mechanistic Studies

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2009
Xinjiang Cui
Abstract The N -alkylation of sulfonamides with alcohols is efficiently performed in the presence of easily available copper catalysts via hydrogen borrowing methodology. Applying a copper acetate/potassium carbonate system the reaction of sulfonamides and alcohols gave the corresponding secondary amines in excellent yield. In situ HR-MS analysis indicated that bissulfonylated amines are formed under air atmosphere, which act as self-stabilizing ligands for the catalytic system. UV-visible measurements suggest the interaction between the copper centre and the bissulfonylated amine. Reactions of benzyl alcohol- d7 with p -toluenesulfonamide, N -benzyl- p -toluenesulfonamide or N -benzylidenetoluenesulfonamide revealed that the reaction proceeds via a transfer hydrogenation mechanism and the whole process is micro-reversible. Competitive reactions of benzyl alcohol and benzyl alcohol- d7 with p -toluenesulfonamide revealed a kinetic isotope effect (kH/kD) of 3.287 (0.192) for the dehydrogenation of benzyl alcohol and 0.611 (0.033) for the hydrogenation of the N -benzylidene- p -toluenesulfonamide intermediate, which suggests that dehydrogenation of the alcohol is the rate-determining step. [source]


Palladium-Catalyzed Asymmetric Allylic Alkylation of 2,3-Allenyl Acetates Using a Chiral Diaminophosphine Oxide

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009
Tetsuhiro Nemoto
Abstract An enantioselective synthesis of allenes through palladium-catalyzed asymmetric allylic alkylation using a chiral diaminophosphine oxide is described. The asymmetric allylic alkylations proceeded in the presence of a catalytic amount of lithium acetate at 4,C, affording the chiral allenes in excellent yield with up to 99% ee. [source]


Asymmetric Hydrogenation of ,,,-Unsaturated Ester- Phosphonates

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2009
Yange Huang
Abstract The rhodium-catalyzed asymmetric hydrogenation of readily available ,,,-unsaturated ester-phosphonates affords the corresponding ,-chiral phosphonates in excellent yield and ee. The resulting products are useful multifunctional building blocks applied in the synthesis of physiologically active compounds. [source]


Palladium-Catalyzed Cyclopropanation of Unsaturated Endoperoxides.

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7-8 2009
A New Peroxide-Preserving Reaction
Abstract Unsaturated bicyclic endoperoxides are efficiently cyclopropanated with excess diazomethane in the presence of catalytic palladium(II) acetate [Pd(OAc)2] in a stereoselective manner. This method represents a new peroxide-preserving transformation. Whereas the unsaturated endoperoxides in the [2.2.1],series are attacked by the carbene from the exo face, the analogs with larger bridges are preferentially attacked from the face syn to the peroxo bridge. Only in the case of the benzannelated [2.2.2],system does the attack occur exclusively from the face proximal to the benzene ring. Certain strained cyclopropanated endoperoxides are reduced by diazomethane to give cis -diols. 2-Methylfuran endoperoxide gives rise to cis -1-formyl-2-acetylcyclopropane in excellent yield. [source]


[1.1]Ferrocenophane-1,12-dione as a Precursor of 1,12-Di(cyclopenta-2,4-dienylidene)-[1.1]ferrocenophane, a Doubly Bridged Difulvene

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7-8 2009
Jos Ramon Garabatos-Perera
Abstract An improved synthesis of [1.1]ferrocenophane-1,12-dione (2) by oxidation of [1.1]ferrocenophane with 2,3-dichloro-5,6-dicyano- p -benzoquinone (DDQ) is presented. The syn conformer of dione 2 is structurally characterized. The compound undergoes various addition reactions at the bridging carbonyl groups. Attempts to add 1,1,-dilithioferrocene result, however, in the diadduct 9, not in the symmetric trinuclear diol 8. Reaction of 2 with sodium cyclopentadienide in the presence of aluminium trichloride (AlCl3) gives the respective difulvene 11 in excellent yield. The dynamic behavior of 11 is investigated by variable temperature 1H,NMR measurements (VT-NMR). The cyclovoltammogram of 11 indicates two reversible oxidation steps. Reduction of difulvene 11 with lithium aluminium hydride (LiAlH4) results in the formation of [1.1]ferrocenophane 12 with cyclopentadienyl anion substituents at either one of the two bridges. While attempts to generate a third ferrocene moiety by reaction with iron(II) choride (FeCl2) have failed so far, the formation of 12 is established by protonolysis and methylation reactions. [source]


Iron(III) Salt-Catalyzed Nazarov Cyclization/Michael Addition of Pyrrole Derivatives

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009
Masamune Fujiwara
Abstract The Nazarov cyclization of two types of pyrrole derivatives was effectively catalyzed by 5,mol% alumina-supported iron(III) perchlorate [Fe(ClO4)3,Al2O3 ] which provided the desired cyclization with high trans selectivity in good to excellent yield. The cyclized product was next reacted with a vinyl ketone in the presence of the same iron salt to afford the corresponding Michael product. A sequential type Nazarov/Michael reaction of pyrrole derivatives has also been accomplished; the synthetic route to 4,5-dihydrocyclopenta[b]pyrrol-6(1,H)-one derivative 5 or 5,6-dihydrocyclopenta[b]pyrrol-4(1,H)-one derivative 6 has thus been established using a very economical iron catalyst. [source]


Convenient General Asymmetric Synthesis of Roche Ester Derivatives through Catalytic Asymmetric Hydrogenation: Steric and Electronic Effects of Ligands

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2008
Cyrielle Pautigny
Abstract An efficient and concise asymmetric hydrogenation of acrylate esters promoted by the cationic ruthenium monohydride complex [Ru(H)(,6 -cot)SYNPHOS]+BF4, is reported. A full investigation of the effects of catalyst precursors, solvents, temperature, hydrogen pressure, substrates as well as steric and electronic properties of ligands was carried out. The corresponding valuable Roche ester derivatives were obtained in good to excellent isolated yields and high enantioselectivities under mild conditions. The robustness and practicability of this highly enantioselective hydrogenation was demonstrated by the synthesis of the 3-hydroxy-2-methylpropanoic acid tert -butyl ester on a multigram scale, resulting in excellent yield and ee up to 94%. [source]


Asymmetric Synthesis of the Roche Ester and its Derivatives by Rhodium-INDOLPHOS-Catalyzed Hydrogenation

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2008
Jeroen Wassenaar
Abstract (S)-3-Hydroxy-2-methylpropionate, known as the Roche ester, and several of its derivatives were successfully synthesized through asymmetric rhodium-catalyzed hydrogenation, using INDOLPHOS (diisopropyl{1-[(S)-3,5-dioxa-4-phosphacyclohepta[2,1- a;3,4- a,]dinaphthalen-4-yl]-3-methyl-2-indolyl}phosphine) as the chiral ligand, in excellent yield and the highest ee reported up to now (TOF over 5500,h,1 at 25,C; up to 98% ee at ,40,C). [source]


Improved Turnover Numbers in Palladium-Catalyzed Bisdiene Cyclization-Trapping using N-Heterocyclic Carbene Ligands

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 15 2005
James
Abstract An optimized palladium-N-heterocyclic carbene catalyst system effects the palladium-catalyzed bisdiene cyclization-trapping with phenol at the 0.01% catalyst loading level with a TON of 7.6103 and TOF of 280,h,1, values much higher than typically found for this and related carbocyclizations. The reaction scales well and the trans -substituted six-membered ring product is obtained in excellent yield on a 10-mmole scale without further optimization of the catalyst system or reaction conditions. [source]


Synthesis of N-Heteroaryl(trifluoromethyl)hydroxyalkanoic Acid Esters by Highly Efficient Solid Acid-Catalyzed Hydroxyalkylation of Indoles and Pyrroles with Activated Trifluoromethyl Ketones

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14 2005
Mohammed Abid
Abstract The synthesis of N-heteroaryl(trifluoromethyl)hydroxyalkanoic acid esters by solid acid-catalyzed Friedel,Crafts hydroxyalkylation of indoles and pyrroles with ethyl 3,3,3-trifluoropyruvate and ethyl 4,4,4-trifluoroacetoacetate is described. The inexpensive and readily available K-10 montmorillonite is found to be an efficient catalyst for the synthesis of a wide variety of trifluoromethylated indol-3-yl- and pyrrol-2-yl-hydroxypropionic and -butanoic acid esters. Using a series of substituted indoles and pyrroles the corresponding products were isolated in excellent yield (up to 98%) and 100% selectivity under mild experimental conditions, during very short reaction times. Beyond these, the ease of product isolation, catalyst stability and handling make this process an attractive, environmentally benign alternative for the synthesis of the target compounds. [source]


A Modular Approach to ,-Arylated Carbonyl Compounds via Indium Tris(bistriflylamide)-Catalyzed Regioselective Addition of ,-Ketoesters to 1,3-Diynes

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-13 2005
Masaharu Nakamura
Abstract A modular synthesis of ,-arylated carbonyl compounds has been achieved by the combination of an indium-catalyzed regioselective addition of ,-keto esters to conjugated diynes and a palladium-catalyzed benzannulation reaction. Indium tris(bistriflylamide), In(NTf2)3, was found to be an efficient catalyst for the first addition reaction of ,-keto esters to diynes. The reaction proceeds with perfect regioselectivity to give conjugated enynes in high yield. The second palladium-catalyzed benzannulation proceeds in high to excellent yield and with high regioselectivity for a variety of diynes. This two-step ,-arylation of carbonyl compounds thus proceeds in a catalytic manner without loss of elements in the starting materials. The reaction may be performed in a single pot without isolation of the product of the first step. [source]


Access to indoles via Diels-Alder reactions of 2-vinylpyrroles with maleimides

JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 6 2009
Wayland E. Noland
Variously substituted 2-vinylpyrroles underwent an endo -addition [4+2] cycloaddition reaction with maleimides followed by a spontaneous highly diastereoselective (93,98% de) isomerization to give tetrahydroindoles in moderate to excellent yield. Treatment with activated MnO2 in refluxing toluene provided the corresponding indoles in moderate to good yield. This highly convergent methodology for formation of indoles is versatile and the starting materials are conveniently prepared. J. Heterocyclic Chem., (2009). [source]


DBU-catalyzed three-component one-pot synthesis of highly functionalized pyridines in aqueous ethanol

JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 1 2009
Ritu Mamgain
1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) efficiently catalyzes three-component one-pot condensations of aldehyde, malononitrile, and thiophenol to produce highly functionalized pyridines in excellent yield in aqueous ethanol. J. Heterocyclic Chem., 46, 69 (2009). [source]


A novel synthesis of benzo[h]quinolines and study of their fluorescence properties

JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 6 2007
Madhukar N. Jachak
An elegant synthesis of highly fluorescent benzo[h]quinolines have been accomplished from readily available and highly economical 6-methoxy-1-tetralone in high purity and excellent yield. [source]


Carbon-14 radiosynthesis of combretastatin A-1 (CA1) and its corresponding phosphate prodrug (CA1P)

JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 14 2009
Rodney T. Brown
Abstract The natural product combretastatin A-1 (CA1) is isolated from the African bush willow tree, a member of the Combretaceae family. CA1 has important medicinal value, due in part to its ability to inhibit tubulin assembly. The prodrug combretastatin A-1 diphosphate (CA1P; OXi4503) is currently in human Phase I clinical trials as a vascular disrupting agent. This paper describes the carbon-14 radiosynthesis of [4,- 14C]CA1 and the corresponding phosphate prodrug salt [4,- 14C]CA1P in high specific activity (55,mCi/mmol). The carbon-14 label was introduced by methylation of the C-4, protected phenolic moiety of the CA1 precursor following removal of the tert -butyldimethylsilyl protecting group in the presence of [14C]methyl iodide. This was accomplished in excellent yield without significant Z to E isomerization. The [14C]-precursor ((Z)-1-[3,,[4,- 14C],5,-trimethoxyphenyl]-2-[2,,3,-di-[(isopropyl)oxy]-4,-methoxyphenyl] ethene) was subjected to a de- isopropylation reaction with TiCl4. The tetrabenzyl phosphate derivative of the resulting diol was prepared using fresh dibenzyl phosphite. Debenzylation with trimethylsilylbromide, followed by hydrolysis of the trimethylsilyl ester and adjustment of the pH with dilute aqueous hydrochloric acid yielded [4,- 14C]CA1P with an overall radiochemical yield of 8.4%. Copyright 2009 John Wiley & Sons, Ltd. [source]


Synthesis and properties of the polythiourethanes obtained by the cationic ring-opening polymerization of cyclic thiourethanes

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2006
Daisuke Nagai
Abstract The cationic ring-opening polymerization of a five-membered thiourethane [3-benzyl-1,3-oxazolidine-2-thione (BOT)] with boron trifluoride etherate afforded the corresponding polythiourethane with a narrow molecular weight distribution in an excellent yield. The molecular weight of the polymers could be controlled by the feed ratio of the monomer to the initiator. A kinetic study of the polymerization revealed that the polymerization rate of BOT (1.3 10,2 L mol,1 min,1) was two times larger than that of the six-membered thiourethane [3-benzyltetrahydro-1,3-oxazolidine-2-thione (BTOT); 6.8 10,3 L mol,1 min,1], and the monomer conversion obeyed the first-order kinetic equation. These observations, along with the successful results in the two-stage polymerization, supported the idea that this polymerization proceeded in a controlled manner. Block copolymerizations of BOT with BTOT were also carried out to afford the corresponding di- and triblock copolymers with narrow molecular weight distributions. The order of the 5% weight loss temperatures was as follows: poly(3-benzyltetrahydro-1,3-oxazolidine-2-thione) [poly(BTOT)] > poly(BTOT54 - b -BOT46) > poly(3-benzyl-1,3-oxazolidine-2-thione) [poly(BOT)]. This indicated that an increase in the BTOT unit content raised the decomposition temperature. The order of the refractive indices was poly(BOT) > poly(BTOT54 - b -BOT46) > poly(BTOT54 - b -BOT46 - b -BTOT50) > poly(BTOT); this was in accord with the order of the sulfur content in the polymer chain. 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4795,4803, 2006 [source]


2-Pyridylquinoxaline derivatives as N,N -ligands for palladium-catalyzed Suzuki,Miyaura reaction

APPLIED ORGANOMETALLIC CHEMISTRY, Issue 8 2009
Yundong Liu
Abstract The Suzuki,Miyaura reaction of aryl bromides with benzeneboronic acid catalyzed by bis(chloro)(2-pyridylquinoxaline)palladium(II) was investigated. The scope of the bis(chloro)(2-pyridylquinoxaline)palladium(II) was determined in toluene at 80 C using KOH as base. Using a 0.1% molar ratio of bis(chloro)(2-pyridylquinoxaline)palladium(II) C1 as a catalyst, aryl bromides reacted with benzeneboronic acid to afford diaryl derivatives in excellent yield. Copyright 2009 John Wiley & Sons, Ltd. [source]