Home About us Contact
|
Home About us Contact | ||
|
|
||
Methyl Iodide (methyl + iodide)
Selected AbstractsA Simple and Practical Protocol for the Palladium-Catalyzed Cross-Coupling of Boronic Acids with Methyl Iodide.CHEMINFORM, Issue 8 2005Lukas J. Goossen No abstract is available for this article. [source] Rapid Methylation of Terminal Acetylenes by the Stille Coupling of Methyl Iodide with Alkynyltributylstannanes: A General Protocol Potentially Useful for the Synthesis of Short-Lived 11CH3 -Labeled PET Tracers with a 1-Propynyl Group.CHEMINFORM, Issue 20 2004Takamitsu Hosoya Abstract For Abstract see ChemInform Abstract in Full Text. [source] Pd0 -Mediated Rapid Coupling between Methyl Iodide and Heteroarylstannanes: An Efficient and General Method for the Incorporation of a Positron-Emitting 11C Radionuclide into Heteroaromatic Frameworks,CHEMISTRY - A EUROPEAN JOURNAL, Issue 45 2009Masaaki Suzuki Prof. Abstract The Pd0 -mediated rapid trapping of methyl iodide with an excess amount of a heteroaryl-substituted tributylstannane has been investigated with the aim of incorporating a short-lived 11C-labelled methyl group into the heteroaromatic carbon frameworks of important organic compounds, such as drugs with various heteroaromatic structures, in order to execute a positron emission tomography (PET) study of vital systems. The reaction was first performed by using our previously developed CH3I/stannane/[Pd2(dba)3]/P(o -CH3C6H4)3/CuCl/K2CO3 (1:40:0.5:2:2:2) system in DMF at 60,°C for 5,min (conditions A), however, the reaction gave low yields for various heteroaromatic compounds. Increasing the amount of phosphine ligand (conditions B) led to a significant improvement in the yield, but the conditions were still not suitable for a range of basic heteroaromatic structures. Use of the CuBr/CsF system (conditions C) also provided a result similar to that obtained under conditions B with an increased amount of the phosphine. Thus, pyridine and related heteroaromatic compounds remained less reactive substrates. The problem was overcome by replacing the DMF solvent with N -methyl-2-pyrolidinone (NMP). The reaction in NMP at 60,100,°C for 5,min using a CH3I/stannane/[Pd2(dba)3]/P(o -CH3C6H4)3/CuBr/CsF (1:40:0.5:16:2:5) combination (conditions D) gave the methylated products in yields of more than 80,% (based on the reaction of CH3I) for all of the heteroaromatic compounds listed in this study. Thus, the combined use of NMP and an increased amount of phosphine is important for promoting the reaction efficiently. The use of this general approach to rapid methylation has been well demonstrated by the synthesis of the PET tracers 2- and 3-[11C]methylpyridines by using [Pd2(dba)3]/P(o -CH3C6H4)3/CuBr/CsF (1:16:2:5) in NMP at 60,°C for 5,min, which gives the desired products in HPLC analytical yields of 88 and 91,%, respectively. [source] Preferred Phosphorus Ylide Formation Upon Alkylation of Lithiobis(diphenylphosphanyl)acetonitrile,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2007Leonie Braun Abstract Deprotonation of the readily available chelate phosphane bis(diphenylphosphanyl)acetonitrile (6) leads to stabilized carbanion system 7. Lithiobis(diphenylphosphanyl)acetonitrile (7) features a unique thf-stabilized monomeric structure in the crystal form with a short cyanonitrogen,Li contact. Alkylation of 7 with n -alkyl bromides (R,Br, R = ethyl, n -propyl, n -butyl, n -hexyl) takes place selectively at one phosphorus atom to yield stabilized ylides 8a,d (two examples characterized by X-ray diffraction). Treatment of 7 with the more reactive alkylation agents methyl iodide or benzyl bromide results in alkylation at both phosphorus atoms to give delocalized bis(phosphonium)ylides 9a,b (both characterized by X-ray diffraction). Similarly, the reaction of 7 with 1,3-dibromopropane or 1,4-dibromobutane yields six- and seven-membered heterocyclic bis(phosphonium)ylides 10a,b, respectively. The spectroscopic characterization and X-ray crystal structure analysis again indicate the presence of delocalized Ph2RP,C(CN),PRPh2 substructures. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Gaseous diffusion coefficients of methyl bromide and methyl iodide into air, nitrogen, and oxygenHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 6 2009Naoki Matsunaga Abstract The gaseous diffusion coefficients of methyl bromide (CH3Br) and methyl iodide (CH3I) into dry air, nitrogen, and oxygen have been measured in the temperature range 303,453 K and at atmospheric pressure via the Taylor dispersion method. Both for methyl bromide and methyl iodide, the diffusion coefficients do not vary in practice on substituting pure nitrogen or oxygen for dry air. The diffusion coefficients for methyl iodide are systematically smaller than those for methyl bromide by about 11%. For the methyl iodide-oxygen system, the effect of the thermal decomposition of methyl iodide has been observed at 453 K. The present results can be reproduced well by the functional form D = ATB, where D (cm2s,1) is the diffusion coefficient at 101 325 Pa (1 atm) and T (K) is the absolute temperature. The constants A and B are as follows: methyl bromide-(air, nitrogen, oxygen), A = 5.57 × 10,6, B = 1.76; methyl iodide-(air, nitrogen, oxygen), A = 5.26 × 10,6, B = 1.75. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20255 [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] Nonequilibrium solvent polarization in kinetics of SN2 reactionsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 2 2003J. S. JaworskiArticle first published online: 21 NOV 200 The solvent effect on the experimental activation barriers for the reactions of methyl iodide with chloride and thiocyanate ions was analyzed according to the Marcus and Shaik theories, considering SN2 mechanism in terms of a single electron shift. The linear increase in the solvent reorganization energy of the Marcus theory (after removing contributions from the specific solvation) with the solvent Pekar factor, describing the effect of the nonequilibrium solvent polarization, was observed for six aprotic solvents. The direct support of the title effect based on the Shaik theory was less evident; however, in general, the calculated activation barriers in 10 solvents change parallel with the experimental ones. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 35: 61,66, 2003 [source] Susceptibility of various developmental stages of the maize weevil, Sitophilus zeamais Motschulsky (Col., Curculionidae) to methyl iodide in brown riceJOURNAL OF APPLIED ENTOMOLOGY, Issue 1 2005S. I. Faruki Abstract:, The efficacy of methyl iodide (MI) as a fumigant against all developmental stages of the maize weevil, Sitophilus zeamais Motsch. was investigated. Tests were conducted with concentrations of 1.5, 1.8, 2.1, 2.4, 2.7 and 3.0 mg/l, for a 6-h exposure period. Values of LC50, LC95 and LC99 of MI for immatures and adult stages were determined. The present laboratory tests showed that MI was toxic to various life stages of S. zeamais at relatively short exposure periods. At the LC50 and LC95 levels, the most susceptible stage was the egg stage followed by larvae, pupae and adults (1-day mortality). The egg was found to be most susceptible to MI, requiring 0.81 and 2.16 mg/l for 50 and 99% mortality, respectively, while the adult was most tolerant, requiring 2.30 and 3.02 mg/l for 50 and 99% mortality, respectively, based on 1-day mortality count. Pupae were less susceptible to MI than egg and larvae, requiring 1.47 and 3.19 mg/l for 50 and 99% mortality, respectively. Based on the present toxicity tests, MI has the potential for use as a fumigant to control all developmental stages of the maize weevil, S. zeamais. [source] The first synthesis of [2- 13C]phloroglucinolJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 10 2010Laura J. Marshall Abstract A fast and efficient synthesis of [2- 13C]phloroglucinol in six steps from acyclic, non-aromatic precursors is presented, with regioselective placement of a 13C-atom in the aromatic ring. The 13C-label was introduced by reaction of [13C]methyl iodide with methyl 4-chloroformyl butyrate. Cyclization via an intramolecular Claisen condensation, followed by aromatization gave [2- 13C]resorcinol. Following subsequent methylation of the hydroxyl groups, the third hydroxyl group was introduced using an iridium-catalysed C,H activation/borylation/oxidation procedure. Demethylation then yielded the desired [2- 13C]phloroglucinol. Copyright © 2010 John Wiley & Sons, Ltd. [source] Carbon-14 radiosynthesis of combretastatin A-1 (CA1) and its corresponding phosphate prodrug (CA1P)JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 14 2009Rodney 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 of 1-(2,4-dichlorophenyl)-4-cyano-5-(4-[11C]methoxyphenyl)- N -(piperidin-1-yl)-1H -pyrazole-3-carboxamide ([11C]JHU75528) and 1-(2-bromophenyl)-4-cyano-5-(4-[11C]methoxyphenyl)- N -(piperidin-1-yl)-1H -pyrazole-3-carboxamide ([11C]JHU75575) as potential radioligands for PET imaging of cerebral cannabinoid receptorJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 12 2006Hong Fan Abstract Two novel ligands for cerebral cannabinoid receptor (CB1), 1-(2,4-dichlorophenyl)-4-cyano-5-(4-methoxyphenyl)- N -(piperidin-1-yl)-1H -pyrazole-3-carboxamide (JHU75528) and 1-(2-bromophenyl)-4-cyano-5-(4-methoxyphenyl)- N -(piperidin-1-yl)-1H -pyrazole-3-carboxamide (JHU75575) have been synthesized. Both JHU75528 and JHU75575 display a combination of higher binding affinity and lower lipophilicity than those of Rimonabant (SR141716), a high affinity CB1 selective antagonist, and AM281, the only available ligand for emission tomography imaging of CB1 in human subjects. Radiolabeled [11C]JHU75528 and [11C]JHU75575 were prepared by reaction of [11C]methyl iodide with nor-methyl precursors. The average radiochemical yield, specific radioactivity, and radiochemical purity of [11C]JHU75528 were 16%, 235 GBq/µmol (6360 mCi/µmol), and 99%, respectively; those of [11C]JHU75575 were 8%, 196 GBq/µmol (5308 mCi/µmol), and 99%, respectively. Both ligands hold promise as PET radioligands for imaging CB1 receptor. Copyright © 2006 John Wiley & Sons, Ltd. [source] 11C,C bond formation by palladium-mediated cross-coupling of alkenylzirconocenes with [11C]methyl iodideJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 2 2006Frank R. Wuest Abstract A novel 11C,C bond formation based on the palladium-mediated cross-coupling reaction of alkenylzirconocenes with [11C]methyl iodide is described. The conversion of internal alkynes into the corresponding alkenylzirconocenes followed by transmetalation with Pd(PPh3)4 and subsequent cross-coupling with [11C]methyl iodide gave several 11C-labelled ,,,,-dimethyl-substituted alkenes. The palladium complex Pd(PPh3)4 proved to be superior to Pt(PPh3)4 or Ni(PPh3)4 as transition metal complex. The scope and limitations of the novel palladium-mediated cross-coupling reaction of alkenylzirconocenes with [11C]methyl iodide were tested with various internal alkynes. After heating at 60°C for 6 min radiochemical yields of up to 75% (based upon [11C]methyl iodide) could be achieved. Copyright © 2006 John Wiley & Sons, Ltd. [source] Synthesis of [11C]celecoxib: a potential PET probe for imaging COX-2 expressionJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 12 2005Jaya Prabhakaran Abstract [11C]Labeling of celecoxib, a COX-2 selective inhibitor and prescription drug for arthritis and pain has been achieved. The precursor molecule for the radiolabeling was synthesized from 4-bromoacetophenone in 4 steps with 23% overall yield. Stille reaction of N-[bis -(4-methoxyphenyl)phenylmethyl]-4-[5-(4-tributylstannylphenyl)-3-trifluoromethylpyrazol-1-yl]benzenesulfonamide (5) with methyl iodide in presence of catalytic amounts of Pd2(dba)3, tri- o -tolylphosphine, CuCl and excess of K2CO3 in DMF followed by deprotection of the sulfonamide with 20% trifluoroaceticacid yielded 4-(5- p -tolyl-3-trifluoromethylpyrazol-1-yl)benzenesulfonamide or celecoxib (6) in 30% yield. However, under identical conditions, synthesis of [11C]celecoxib ([11C]6) was unsuccessful. Instead, trapping [11C]CH3I in an argon purged solution of catalytic amounts of Pd2(dba)3 and tri- o -tolylphosphine followed by the addition of the precursor 5 in DMF under argon and heating the mixture at 135°C for 4 min resulted in the incorporation of [11C]CH3 group. Removal of the dimethoxytrityl (DMT) with 20% trifluoroacetic acid afforded [11C]celecoxib in 40 min (EOB) and 8±2% yield (EOB) along with a specific activity of 1080±180 Ci/mmol (n=6) (EOB). Copyright © 2005 John Wiley & Sons, Ltd. [source] Synthesis of [1- 11C]ethyl iodide from [11C]carbon monoxide and its application in alkylation reactionsJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 11 2004Jonas Eriksson Abstract A method is presented for preparing [1- 11C]ethyl iodide from [11C]carbon monoxide. The method utilizes methyl iodide and [11C]carbon monoxide in a palladium-mediated carbonylation reaction to form a mixture of [1- 11C]acetic acid and [1- 11C]methyl acetate. The acetates are reduced to [1- 11C]ethanol and subsequently converted to [1- 11C]ethyl iodide. The synthesis time was 20 min and the decay-corrected radiochemical yield of [1- 11C]ethyl iodide was 55 ± 5%. The position of the label was confirmed by 13C-labelling and 13C-NMR analysis. [1- 11C]Ethyl iodide was used in two model reactions, an O -alkylation and an N -alkylation. Starting with approximately 2.5 GBq of [11C]carbon monoxide, the isolated decay-corrected radiochemical yields for the ester and the amine derivatives were 45 ± 0.5% and 25 ± 2%, respectively, based on [11C]carbon monoxide. Starting with 10 GBq of [11C]carbon monoxide, 0.55 GBq of the labelled ester was isolated within 40 min with a specific radioactivity of 36 GBq/µmol. Copyright © 2004 John Wiley & Sons, Ltd. [source] Synthesis and evaluation of tritium labelled 10-methylgalanthamine iodide: a novel compound to examine the mechanism of interaction of galanthamine derivatives with the nicotinic acetylcholine receptorsJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 12 2003Andreas Schildan Abstract A new promising galanthamine derivative, 10-[3H]methylgalanthamine iodide, was synthesized for binding studies to nicotinic acetylcholine receptors expressed in Torpedo electric ray electroplaques. Galanthamine was reacted with [3H]methyl iodide to yield 10-[3H]methylgalanthamine iodide with a radiochemical yield of >70% and a specific activity of 32 Ci/mmol after purification via solid phase extraction. To test the ligand properties of the radioligand, calcium imaging and electrophysiology of the non-radioactive analogue were performed to obtain an EC50 of 270 nM, a Hill coefficient of 1.9 and the induced cell current. Copyright © 2003 John Wiley & Sons, Ltd. [source] Preparation of 4-[11C]methylmetaraminol, a potential PET tracer for assessment of myocardial sympathetic innervationJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 1 2003Oliver Langer Abstract The false adrenergic neurotransmitter [11C]meta -hydroxyephedrine ([11C]HED) is currently the PET tracer of choice for assessment of myocardial sympathetic innervation. The molecule is metabolised in the 4-position of the aromatic ring. The resulting radiolabelled metabolites need to be measured in order to obtain an arterial input function. Our aim was the development of a PET tracer with an increased metabolic stability relative to [11C]HED. We selected 4-methylmetaraminol as a candidate molecule for radiolabelling with 11C (t1/2 20.4 min). Our radiosynthetic approach towards 4-[11C]methylmetaraminol involved a palladium-catalyzed cross-coupling reaction of a protected 4-trimethylstannyl derivative of metaraminol with [11C]methyl iodide followed by removal of the protective groups. 4-[11C]methylmetaraminol was obtained in a final decay-corrected radiochemical yield of 20,25% within a synthesis time of 60,80 min. The specific radioactivity at the end of the synthesis ranged from 18,37 to GBq/,mol. The unlabelled reference molecule, 4-methylmetaraminol, was prepared in a 5-step synthesis starting from metaraminol. A biological evaluation of 4-[11C]methylmetaraminol is in progress and the results will be reported elsewhere. Copyright © 2002 John Wiley & Sons, Ltd. [source] Synthesis and 11C-labelling of (E,E)-1-(3,,4,-dihydroxystyryl)-4-(3,-methoxy-4,-hydroxystyryl) benzene for PET imaging of amyloid deposits,,JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 8 2002Yanming Wang Abstract Carboxylic acid derivatives of the amyloid-binding dye Congo red do not enter the brain well and are thus unable to serve as in vivo amyloid-imaging agents. A neutral amyloid probe, (E,E)-1-(3,,4,-dihydroxystyryl)-4-(3,-methoxy-4,-hydroxystyryl)benzene (3), devoid of any carboxylate groups has been designed and synthesized via a 12-step reaction sequence with a total yield of 30%. The unsymmetric compound 3 has also been labelled with C-11 via [11C]methyl iodide ([11C]CH3I) methylation of a symmetric 4,4,-dimesyl protected precursor followed by deprotection. Preliminary evaluation indicated that compound 3 selectively stained plaques and neurofibrillary tangles in post-mortem AD brain, and exhibited good binding affinity (Ki=38±8 nM) for A,(1,40) fibrils in vitro. In vivo pharmacokinetic studies indicated that [11C]3 exhibited higher brain uptake than its carboxylic acid analogs and good clearance from normal control mouse brain. [11C]3 also exhibited specific in vivo binding to pancreatic amyloid deposits in the NOR-beta transgenic mouse model. These results justify further investigation of 3 and similar derivatives as surrogate markers for in vivo quantitation of amyloid deposits. Copyright © 2002 John Wiley & Sons, Ltd. [source] Synthesis and characterization of 4,6-dichloroindole-based radioligands for imaging the glycine site of the NMDA ion channelJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 2 2002R. N. Waterhouse Abstract To provide effective PET or SPECT ligands for the glycine binding site of the NMDA ion channel, we have synthesized and characterized in vitro four substituted derivatives of the potent glycine site antagonist 3-[2-[(phenylamino)carbonyl]ethenyl]-4,6-dichloroindole-2-carboxylic acid (Ki=3.0 nM). These new ligands contain groups amenable to labeling with C-11 for PET, or I-123 for SPECT. In vitro analysis of these compounds revealed that placement of a methoxy group at either the ortho or para position of the phenylaminocarbonyl group significantly reduced receptor affinity (Ki=74.0±8.1 and 26.5±4.9 nM, respectively), as did placement of an iodine at the para position (Ki=60.4±8.2 nM). However, the meta -methoxy derivative (4b) maintained high affinity (Ki=4.8±0.9 nM) for the glycine site and was therefore labeled with carbon-11 by reacting the corresponding desmethyl derivative with [11C]methyl iodide. Radiochemical yields of 14±10% (EOS), and high specific activity (1.2±0.5 Ci/,mol (EOS, n=7)) were realized, and the product was prepared in a sterile saline solution suitable for in vivo use. Copyright © 2002 John Wiley & Sons, Ltd. [source] Precursor synthesis and radiolabelling of [11C]ADAM: a potential radioligand for the serotonin transporter exploration by PETJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 2 2001Johnny VERCOUILLIE Abstract The serotoninergic system is involved in a variety of neurological and psychiatric disorders. Exploration of the serotonin transporters (5-HTT) in living human brain by PET would be of great value for better understanding, diagnosis and therapeutic follow up of these diseases. In order to obtain a selective radioligand to explore the 5-HTT by PET we report the synthesis of [11C]N,N-dimethyl-2-(2-amino-4-iodophenylthio)-benzylamine ([11C]ADAM). The precursor for labelling N-demethyl ADAM, was obtained in five steps using 2,5-dibromonitrobenzene and 2-thio-N-methylbenzamide as starting material. [11C]ADAM was synthesised by N-alkylation of the precursor using [11C]methyl iodide in DMF. The incorporation yield of [11C]methyl iodide was in the range of 50 to 70%. Finally [11C]ADAM was obtained in 30 minutes synthesis time including HPLC and with a radiochemical purity better than 99%. Copyright © 2001 John Wiley & Sons, Ltd. [source] Synthesis of [N -methyl- 11C]mianserin: a tetracyclic, atypical antidepressantJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 2 2001K. Marthi Abstract As part of our program to develop PET tracers for investigating monoaminergic processes in the brain, mianserin, a tetracyclic, atypical antidepressant, was selected as a candidate for labelling with 11C for in vivo evaluation. [N -methyl- 11C]Mianserin was produced by the alkylation of N -desmethyl mianserin with [11C]methyl iodide followed by HPLC purification and formulation. [N -methyl- 11C]Mianserin was obtained with a radiochemical purity >93% in a 16% decay corrected radiochemical yield. For a typical production starting with 40 GBq [11C]CO2, 1.9 GBq [N -methyl- 11C]mianserin was obtained as a formulated solution in a synthesis time of 35 min (counted from EOB). Copyright © 2001 John Wiley & Sons, Ltd. [source] Analysis of alcohols, as dimethylglycine esters, by electrospray ionization tandem mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 3 2001Dr David W. Johnson Abstract Dimethylglycine (DMG) esters are new derivatives for the rapid, sensitive and selective analysis of primary and secondary alcohols, in complex mixtures, by electrospray ionization tandem mass spectrometry (ESI-MS/MS). Their development was inspired by the use of the complementary dimethylaminoethyl esters for the trace, rapid analysis of fatty acids. DMG esters are simply prepared by heating a dichloromethane solution of the imidazolide of dimethylglycine, containing triethylamine, and an alcohol. DMG esters of long-chain fatty alcohols, isoprenoidal alcohols and hydroxy-acids are analysed by electrospray ionization tandem mass spectrometry with a precursor ion of m/z 104 scan. Diols, glyceryl esters, glyceryl ethers and some sterols are analysed by a neutral loss of 103 Da scan. Trimethylglycine (TMG) ester iodides, prepared by alkylation of DMG esters with methyl iodide, are more sensitive derivatives for molecules containing secondary alcohol groups, such as cholesterol and gibberellic acid. They are analysed by a precursor ion of m/z 118 scan. DMG or TMG derivatives were shown to be at least comparable and sometimes an order of magnitude more sensitive than N -methylpyridyl ether derivatives for ESI-MS/MS analysis of the different classes of alcohols. Applications of these derivatives for the diagnosis of inherited disorders and the analysis of natural products are presented. Copyright © 2001 John Wiley & Sons, Ltd. [source] Looking for a contribution of the non-equilibrium solvent polarization to the activation barrier of the SN2 reactionJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 6 2002Jan S. Jaworski Abstract The solvent effect on the activation free energy of the Finkelstein reaction between methyl iodide and Cl, ions was analysed in terms of the recent Marcus theory unifying the SN2 and the electron transfer reactions. The homolytic bond dissociation energy and the related resonance energy of interaction of the states seem to be almost solvent independent. The sum of the work term wr and the solvent reorganization energy ,0/4 depends strongly on the solvent acidity parameter, e.g. ETN, describing the solvation/desolvation of anions. However, after removing the contribution of the specific solvation the linear increase of the remaining part of ,0/4 with the Pekar factor, describing the non-equilibrium solvent polarization, was observed for six aprotic solvents. Copyright © 2002 John Wiley & Sons, Ltd. [source] Switchable thin-film surface prepared via a simple grafting-to method using a polystyrene- b -poly(2-vinylpyridine) copolymerJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2006Ying Wang Abstract A polystyrene- b -poly(2-vinylpyridine) block copolymer containing a methylhydridosilane linking group was chemically grafted to an 8-trichlorosilyloctene monolayer via a simple one-step hydrosilylation reaction. The resulting Y-shaped thin film exhibited a low grafting density, which was characteristic of the grafting-to technique. To further reduce the miscibility of the two arms, methyl iodide was reacted with the poly(2-vinylpyridine) block to produce quaternary ammonium groups. The surfaces before and after quaternization were both solvent-switchable when subjected to block-selective solvents. Tensiometry, ellipsometry, attenuated total reflection/Fourier transform infrared, and atomic force microscopy were used to characterize the properties and morphology of both unquaternized and quaternized samples. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5608,5617, 2006 [source] Cationic, water-soluble, fluorene-containing poly(arylene ethynylene)s: Effects of water solubility on aggregation, photoluminescence efficiency, and amplified fluorescence quenching in aqueous solutionsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2006Yan-Qin Huang Abstract Three novel fluorene-containing poly(arylene ethynylene)s with amino-functionalized side groups were synthesized through the Sonogashira reaction. They were poly{9,9-bis[6,-(N,N -diethylamino)hexyl]-2,7-fluorenylene ethynylene}- alt - co -{2,5-bis[3,-(N,N -diethylamino)-1,-oxapropyl]-1,4-phenylene} (P1), poly{9,9-bis[6,-(N,N -diethylamino)hexyl]-2,7-fluorenylene ethynylene} (P2), and poly({9,9-bis[6,-(N,N -diethylamino)hexyl]-2,7-fluorenylene ethynylene}- alt - co -(1,4-phenylene)) (P3). Through the postquaternization treatment of P1,P3 with methyl iodide, we obtained their cationic water-soluble conjugated polyelectrolytes (WSCPs): P1,,P3,. The water solubility was gradually improved from P3, to P1, with increasing contents of hydrophilic side chains. After examining the ultraviolet,visible absorption and photoluminescence (PL) spectra, fluorescence lifetimes, and dynamic light scattering data, we propose that with the reduction of the water solubility from P1, to P3,, they exhibited a gradually increased degree of aggregation in H2O. The PL quantum yields of P1,,P3, in H2O displayed a decreasing tendency consistent with the increased degree of aggregation, suggesting that the pronounced degree of aggregation was an important reason for the low PL quantum yields of WSCPs in H2O. Two structurally analogous water-soluble trimers of P2, and P3,, model compounds 2,7-bis(9,,9,-bis{6,-[(N,N -diethyl)- N -methylammonium] hexyl}-2,-fluorenylethynyl)-9,9-bis{6,-[(N,N -diethyl)- N -methylammonium]hexyl}fluorene hexaiodide and 1,4-bis(9,,9,-bis{6,-[(N,N -diethyl)- N -methylammonium]hexyl}-2,-fluorenylethynyl)benzene tetraiodide, were synthesized. The amplified fluorescence quenching of these WSCPs by Fe(CN)64, in H2O was studied by comparison with a corresponding analogous trimer. The effects of aggregation on the fluorescence quenching may be two-edged in these cases. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5778,5794, 2006 [source] pH-Switchable Complexation between Double Hydrophilic Heteroarm Star Copolymers and a Cationic Block PolyelectrolyteMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 7 2008Zhishen Ge Abstract Double hydrophilic heteroarm star copolymers of poly(methacrylic acid) (PMAA) and poly(ethylene oxide) (PEO) were synthesized via atom-transfer radical polymerization (ATRP) using the "in-out" method. The synthesis consisted of three steps. Namely, ATRP was applied to the preparation of a star macroinitiator with PEO arms and a cross-linked core resulting from the polymerization of divinylbenzene (DVB) in the first step, chain extension with tert -butyl methacrylate (tBMA) under ATRP conditions, and subsequent hydrolysis of the tert -butyl groups afforded (PEO)n -PDVB-(PMAA)n heteroarm star copolymers with a cross-linked microgel core. This novel type of double hydrophilic heteroarm star copolymer can be considered as unimolecular micelles with hybrid coronas. The star copolymers exhibited pH-dependent solubility in water, being soluble at high pH and insoluble at low pH, due to the formation of hydrogen-bonded complexes between the PEO and PMAA arms. A mixed solution of the heteroarm star copolymer and a PEO- b -PQDMA diblock copolymer, where PQDMA is poly(2-(dimethylamino)ethyl methacrylate) fully quaternized with methyl iodide, remained stable in the whole pH range, and exhibited an intriguing pH-switchable complexation behavior accompanied with structural rearrangement. [source] Physical, chemical and environmental properties of selected chemical alternatives for the pre-plant use of methyl bromide as soil fumigantPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 2 2006Luis O Ruzo Abstract Production and use of methyl bromide, a soil fumigant, are being restricted because of this chemical's deleterious effects on stratospheric ozone concentrations. Several products, some of which are currently used as soil fumigants, are being considered as possible replacements for methyl bromide, alone and in various combinations. Among these, 1,3-dichloropropene, methyl isothiocyanate generators such as metam-sodium, and chloropicrin are currently registered, while others such as methyl iodide and sodium azide are at different stages of the registration process. This review examines physicochemical properties, environmental fate, and metabolism of the various potential methyl bromide replacement products. Copyright © 2005 Society of Chemical Industry [source] Solid-phase permethylation of glycans for mass spectrometric analysisRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2005Pilsoo Kang A miniaturized approach was developed for quantitative permethylation of oligosaccharides, which involves packing of sodium hydroxide powder in microspin columns or fused-silica capillaries (500,µm i.d.), permitting effective derivatization in less than a minute at microscale. Prior to mass spectrometry, analytes are mixed with methyl iodide in dimethyl sulfoxide solution containing traces of water before infusing through the microreactors. This procedure minimizes oxidative degradation and peeling reactions and avoids the need of excessive clean-up. Picomole amounts of linear and branched, sialylated and neutral glycan samples were rapidly and efficiently permethylated by this approach and analyzed by matrix-assisted laser desorption/ionization mass spectrometry. Copyright © 2005 John Wiley & Sons, Ltd. [source] Me3SiCl and Et3SiI-promoted one-pot synthesis of 1,4-dihydropyridine derivativesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 7 2009Maryam Mirza-Aghayan Abstract An efficient synthesis of 1,4-dihydropyridine derivatives has been achieved by the one-pot cyclocondensation reaction of methyl 3-aminocrotonate and a range of aldehydes in the presence of chlorotrimethylsilane as a promoter under solvent-free conditions. The cyclocondenstion reaction requires a very short time and takes place in good to excellent yields. Furthermore iodotriethylsilane, generated in situ by the reaction of triethylsilane and methyl iodide in the presence of palladium chloride, has been investigated for the synthesis of 1,4-dihydropyridine derivatives. This facile and efficient method affords high yields for the preparation of 1,4-dihydropyridines at room temperature and short reaction times. Copyright © 2009 John Wiley & Sons, Ltd. [source] Methylation of tin(II) by methyl iodide: influences of different environmental factors on the efficiency and reaction kineticsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 3 2006Chen Baowei Abstract The methylation reaction of Sn(II) with methyl iodide (MeI) in water has been studied using sensitive GC-QSIL-FPD technology. The pH value, amount of MeI and salinity (S) are the three important factors that influence the methylation reaction in an aquatic environment. In all experiments, monomethyltin (MMT) is the only methylation product of the tin(II) reacting with MeI observed. At the 95% confidence level, the pH, MeI and S are significant for the MMT yield. The concentration of MMT in the reactor increases with increase in pH within the selected pH range of 4,9 because four different species of Sn(II),Sn2+, SnOH+, Sn(OH)20 and Sn(OH)3,,have different reaction activities with MeI. The methylation activity of Sn(II) was found to be highest at a salinity of 0.1 M at three different pH levels: 5, 7 and 9. Higher concentration of Cl, (as a relatively weak nucleophilic ion) will obstruct nucleophilic attack of Sn(II) on MeI. MMT production also increases with rising volume of MeI. Moreover, first-order reaction rates have been calculated at different pH, salinity and MeI, and found to be in the range 0.0018,0.0199 h,1. The reaction rate also varies largely under different reaction conditions. One probable mechanism for the methylation reaction of Sn(II) with MeI is a SN2 nucleophilic attack on the methyl group of MeI by Sn(II), via a process of oxidative methyl-transfer. Copyright © 2006 John Wiley & Sons, Ltd. [source] Pd0 -Mediated Rapid Coupling between Methyl Iodide and Heteroarylstannanes: An Efficient and General Method for the Incorporation of a Positron-Emitting 11C Radionuclide into Heteroaromatic Frameworks,CHEMISTRY - A EUROPEAN JOURNAL, Issue 45 2009Masaaki Suzuki Prof. Abstract The Pd0 -mediated rapid trapping of methyl iodide with an excess amount of a heteroaryl-substituted tributylstannane has been investigated with the aim of incorporating a short-lived 11C-labelled methyl group into the heteroaromatic carbon frameworks of important organic compounds, such as drugs with various heteroaromatic structures, in order to execute a positron emission tomography (PET) study of vital systems. The reaction was first performed by using our previously developed CH3I/stannane/[Pd2(dba)3]/P(o -CH3C6H4)3/CuCl/K2CO3 (1:40:0.5:2:2:2) system in DMF at 60,°C for 5,min (conditions A), however, the reaction gave low yields for various heteroaromatic compounds. Increasing the amount of phosphine ligand (conditions B) led to a significant improvement in the yield, but the conditions were still not suitable for a range of basic heteroaromatic structures. Use of the CuBr/CsF system (conditions C) also provided a result similar to that obtained under conditions B with an increased amount of the phosphine. Thus, pyridine and related heteroaromatic compounds remained less reactive substrates. The problem was overcome by replacing the DMF solvent with N -methyl-2-pyrolidinone (NMP). The reaction in NMP at 60,100,°C for 5,min using a CH3I/stannane/[Pd2(dba)3]/P(o -CH3C6H4)3/CuBr/CsF (1:40:0.5:16:2:5) combination (conditions D) gave the methylated products in yields of more than 80,% (based on the reaction of CH3I) for all of the heteroaromatic compounds listed in this study. Thus, the combined use of NMP and an increased amount of phosphine is important for promoting the reaction efficiently. The use of this general approach to rapid methylation has been well demonstrated by the synthesis of the PET tracers 2- and 3-[11C]methylpyridines by using [Pd2(dba)3]/P(o -CH3C6H4)3/CuBr/CsF (1:16:2:5) in NMP at 60,°C for 5,min, which gives the desired products in HPLC analytical yields of 88 and 91,%, respectively. [source] | |||||||||||||||||||||||||