- Di- and Tri-valent Complexes of Ytterbium via Novel Metal Oxidation
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Oxidation of Yb metal by iodopentamethylcyclopentadiene (IC5Me5) afforded Li and Li sequentially in the presence of LiI; analogous anionic chloride complexes, the new divalent complex Yb(C5Me5)2, and methyl derivatives of both d
- Watson, Patricia L.
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- Synthesis of 8-alkylthio- and 8-selanyl-3-tert-butylpyrazolo[5,1-c][1,2,4]triazines
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Interaction of 8-lithio-3-tert-butyl-4-oxopyrazolo[5,1-c][1,2,4]triazin-1-ide with elemental sulfur or selenium in THF with further in situ alkylation at –97 °C followed by warming to room temperature furnished a series of 3-tert-butyl-8-X-pyrazolo[5,1-c][1,2,4]triazin-4(6H)-ones (X = n-BuS, n-BuSe, MeSe, PhCH2S) in good yields. 8,8'-Diselanediylbis(3-tert-butylpyrazolo[5,1-c][1,2,4]triazin-4(1H)-one) was also isolated as a by-product in these reactions. One-pot interaction of the n-BuSe substituted derivative with diborane/boron trifluoride led to reduction of the 1,2,4-triazine core and partial elimination of the alkylselanyl moiety. The structures of the synthesized products were established on the basis of IR, 1H, 13C, 2D HMBC 1H–77Se NMR and high resolution mass spectra, as well as X-ray single crystal diffraction analyses. Two of the prepared compounds were also tested for antimicrobial and antifungal activities.
- Ivanov, Sergey M.,Minyaev, Mikhail E.,Mironovich, Lyudmila M.
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- Preparation and Crystal Structure of the Addition Compound MeLi*U4, a Compound with a Uranium to Carbon ?-Bond
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Reaction of MeLi and U4 gives the additioncompound, LiU(Me)4 which in the solid state has a geometry based upon square pyramidal uranium with the apical site occupied by a methyl group and the four basal sites being occupied by oxygen atoms of the alkoxide ligand, two of which form bridges to the lithium atom.
- Stewart, Joanne L.,Andersen, Richard A.
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- A new strategy for the synthesis of organosilicon compounds of cyclopropane derivatives
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The one-pot reaction of tetra-substituted cyclopropyl benzyl bromide with tris(trimethylsilyl)methyllithium (TsiLi) and carbon disulfide resulted in 3-(4-((((trimethylsilyl)ethynyl)thio)methyl)phenyl)cyclopropane-1,1,2,2-tetracarbonitrile (3) and 3-(4-((trimethylsilyl)methyl)phenyl)cyclopropane-1,2-dicarbonitrile (4) in excellent yield. The reaction in the absence of carbon disulfide yielded 3-(4-(2,2,2-tris(trimethylsilyl)ethyl)phenyl)cyclopropane-1,1,2,2-tetracarbonitrile (5) in excellent yield at 08C to room temperature. All structures were characterised by IR, 1H NMR, and 13C NMR spectroscopies. The reaction mechanisms are discussed.
- Gholizadeh, Saeed,Safa, Kazem D.,Pesyan, Nader Noroozi
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p. 245 - 251
(2020/11/10)
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- Elongated Gilman cuprates: The key to different reactivities of cyano- and iodocuprates
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In the past the long-standing and very controversial discussion about a special reactivity of cyano- versus iodocuprates concentrated on the existence of higher-order cuprate structures. Later on numerous structural investigations proved the structural equivalence of iodo and cyano Gilman cuprates and their subsequential intermediates. For dimethylcuprates similar reactivities were also shown. However, the reports about higher reactivities of cyanocuprates survived obstinately in many synthetic working groups. In this study we present an alternative structural difference between cyano- and iodocuprates, which is in agreement with the results of both sides. The key is the potential incorporation of alkyl copper in iodo but not in cyano Gilman cuprates during the reaction. In the example of cuprates with a highly soluble substituent (R = Me 3SiCH2) we show that in the case of iodocuprates during the reaction several copper-rich complexes are formed, which consume additional iodocuprate and provide lower reactivities. To confirm this, a variety of highly soluble copper-rich complexes were synthesized, and their molecular formulas, the position of the equilibriums, their monomers and their aggregation trends were investigated by NMR spectroscopic methods revealing extended iodo Gilman cuprates. In addition, the effect of these copper-rich complexes on the yields of cross-coupling reactions with an alkyl halide was tested, resulting in reduced yields for iodocuprates. Thus, this study gives an explanation for the thus far confusing results of both similar and different reactivities of cyano- and iodocuprates. In the case of small substituents the produced alkyl copper precipitates and similar reactivities are observed. However, iodocuprates with large substituents are able to incorporate alkyl copper units. The resulting copper-rich species have less polarized alkyl groups, i.e. gradually reduced reactivities.
- Neumeier, Maria,Gschwind, Ruth M.
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p. 5765 - 5772
(2014/05/06)
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- Functionalized α-bromocyclopropylmagnesium bromides: Generation and some reactions
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Functional derivatives of gem-dibromocyclopropanes (ethers and esters of gemdibromocyclopropylmethanol, 2,2-dibromocyclopropanecarboxylic acids and their esters) undergo partial hydrodebromination at the treatment with isopropyl magnesium bromide (3-6 mol-equiv) in THF and then in methanol at -60°C affording the corresponding monobromides in 64-95% yields. The addition of nonsolvated magnesium bromide to the reaction mixture results in the considerable reduction of the amount of the Grignard reagent (from 6 to 3 mol-equiv). This allows achieving the partial hydrodebromination of 2,2-dibromocyclopropanecarboxylic acids. Pleiades Publishing, Ltd., 2013.
- Bolesov,Solov'eva,Baird
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p. 1580 - 1589
(2014/02/14)
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- Synthesis agent containing methyllithium/lithium bromide and processes for its preparation
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Methyl lithium and lithium bromide containing synthetic agent (A) comprises a solvent (I), where the methyl lithium and lithium bromide are dissolved and the molar ratio of lithium bromide to methyl lithium is at least 0.7 and maximum 1.5. Methyl lithium and lithium bromide containing synthetic agent (A) comprises a solvent (I) of formula C(R 1>)(R 2>)(OR 3>)(OR 4>), where the methyl lithium and lithium bromide are dissolved and the molar ratio of lithium bromide to methyl lithium is at least 0.7 and maximum 1.5. R 1>, R 2>H, CH 3 or CH 2CH 3; and R 3>, R 4>CH 3 or CH 2CH 3. Independent claims are also included for the preparations of (A).
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Page/Page column 6
(2008/06/13)
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- The cocondensation reaction of lithium atoms and anisole: An experimental and theoretical study of the reaction pathway
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The cocondensation reaction of lithium atoms and pure anisole leads to an ortho CH activation and the formation of lithium hydride. This simple two-component system allows the investigation of the reaction mechanism with included donor molecules. Therefore two anisole and one dilithium molecule, which was identified in an earlier spectroscopic study, were considered for the reaction pathway calculations. Firstly, two intermediates can be found along the reaction pathway, which show the reaction before and after the critical CH activation step. Secondly, a low-lying transition state can be identified, which allows the carbon hydrogen bond to be broken with an activation energy of less than 20 kcal/mol instead of more than 100 kcal/mol, if a free radical mechanism is employed. All calculations were performed at the B3LYP/6-31G** level of theory.
- Mendoza, Oscar,Cuffe, Laurence P.,Rehmann, Franz-Josef K.,Tacke, Matthias
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p. 1511 - 1522
(2007/10/03)
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- Lithium-2-2'-biphenyldiyltrimethylsilicat: erstmalige Beobachtung von Pentaorganosilicaten
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Keywords: Lithiumverbindungen; NMR-Spektroskopie; Siliciumverbindungen; Substitutionen
- Keijzer, Adrianus H. J. F. de,Kanter, Franciscus J. J. de,Schakel, Marius,Schmitz, Robert F.,Klumpp, Gerhard W.
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p. 1183 - 1184
(2007/10/03)
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- Diastereoselective Addition of Organometallics to N-(α-Ketoacyl)-trans-2,5-bis(methoxymethoxymethyl)pyrrolidine
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The nucleophilic addition of organometallics to α-keto amides having (2R,5R)-trans-2,5-bis(methoxymethoxymethyl)pyrrolidine as a chiral auxiliary was studied and it was found that the sense and degree of diastereoselection strongly depended on organometallics and the reaction conditions used and that the diastereomeric hydroxy amides was obtained with high stereoselectivity by the choice of appropriate reaction conditions.
- Kawanami, Yasuhiro,Fujita, Izumi,Ogawa, Shiho,Katsuki, Tsutomu
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p. 2063 - 2066
(2007/10/02)
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- The chemistry of bulky chelating phosphines. 3. Anionic alkyl and aryl complexes of rhodium(I) and iridium(I)
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A series of thermally stable anionic dialkyl-, diaryl-, and dialkynylrhodium(I) and dialkyl-, diaryl- and dialkynyliridium(I) bis(phosphine) complexes of the general formula (dtbpe)MR2Li(OR′2)x (M = Rh, Ir; dtbpe = 1,2-bis(di-tert-butylphosphino)ethane) have been prepared and characterized by 1H, 31P{1H}, and 13C{1H} NMR spectroscopy. The anionic complexes are monomeric in polar and nonpolar solvents as determined by multinuclear NMR spectroscopy. Crossover experiments indicate that the complexes (dtbpe)MR2Li(OR′2)x are inert with respect to exchange of their hydrocarbon ligands in solution. Protonation of (dtbpe)MR2Li(OR′2)x affords either {(μ-OH)Ir(dtbpe)}2 (H2O) or {(μ-H)Rh(dtbpe)}2 (i-PrOH). The latter reaction apparently proceeds via a series of protonation/reductive elimination sequences followed ultimately by a β-hydride abstraction from the coordinated alkoxide ligand. The (dtbpe)MR2Li(OR′2)x complexes also act as mild alkylating agents toward transition-metal halide complexes.
- Del Paggio, Alan A.,Andersen, Richard A.,Muetterties, Earl L.
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p. 1260 - 1267
(2008/10/08)
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- Asymmetric Synthesis of Clerodane Diterpenoids: Total Synthesis of (-)-Methyl Kolavenate
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The asymmetric synthesis of (8R,9S,10R)-4,8,9-trimethyl-9-vinyl-Δ4-3-octalone, a versatile intermediate for the syntheses of both trans- and cis-neo-clerodane diterpenoids, has been achieved by extension of Ender's asymmetric alkylation, and its utility is exemplified by the total synthesis of (-)-methyl kolavenate, the first example of a clerodane diterpenoid in optically active form.
- Iio, Hideo,Monden, Mitsugu,Okada, Kimikazu,Tokoroyama, Takashi
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p. 358 - 359
(2007/10/02)
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- STUDIES ON THE ASYMMETRIC TOTAL SYNTHESIS OF TRICHOTHECENES. STEREOSELECTIVE CONSTRUCTION OF THE C-RING FRAGMENT
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A stereoselective construction of the C-ring fragment of trichothecenes from readily available 4-cumyloxy-2-cyclopentenol in 12 steps (24percent overall yield) is described.
- Hua, Duy H.,Venkataraman, S.
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p. 3765 - 3768
(2007/10/02)
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- Dialkyl, Diaryl, and Alkyl Aryl Complexes of Ruthenium(II)
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Whereas HgR2 (R=methyl or aryl) converts trans-(Ru(CO)2Cl2(PMe2Ph)2) exclusively into (Ru(CO)2R(Cl)(PMe2Ph)2) and does not react with cis-(Ru(CO)2Cl2(PMe2Ph)2), LiR reacts with either isomer to yield (Ru(CO)2R2(PMe2Ph)2) and also catalyses conversion of the trans isomer into the cis.The initial attack by R- is belived to be on a carbonyl ligand.Treatment of (Ru(CO)2R(Cl)(PMe2Ph)2) with LiR' yields mixed complexes (Ru(CO)2R(R')(PMe2Ph)2).In all cases the two organic ligands are mutually cis.The dimethyl complex undergoes reversible carbonylation to form mono- and di-acetyl complexes, and (Ru(CO)2Me(Ph)(PMe2Ph)2) also forms an acetyl coplex, but aryl ligands are unaffected by treatment with CO.
- Saunders, David R.,Stephenson, Martin,Mawby, Roger J.
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p. 2473 - 2478
(2007/10/02)
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- Formation of Peralkylcyclohexadienyllithium Compounds
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1,1,2,3,5,6-Hexamethyl-4-methylene-2,5-cyclohexadiene (1) reacts with alkyllithium compounds, RLi (R= n-Bu, sec-Bu, and t-Bu), at 2O deg C in hydrocarbon solution or in the presence of ethers or tertiary amines, which act as ligands, to give stable, soluble 1,1,2,3,5,6-hexamethyl-4-alkylcyclohexadienyllithium compounds, 3a-c.On heating, the latter aromatize to pentamethylalkylbenzenes, 4a-c, with extrusion of methyllithium, while on hydrolysis of 3a-c isomeric substituted cyclohexadienes are obtained.The effects have been investigated of varying RLi structure, ligand, and temperature on the rates of addition and aromatization reactions.Ligand metalation by RLi is a significant side reaction.Addition is faster with ligands known to reduce the association of alkyllithium compounds.Aromatization is faster in the presence of THF which favors formation of loose ion pairs and is slower with heavy substitution on the ring.It is proposed that large substituents (neopentyl) destabilize the transition states for aromatization due to steric interactions.
- Hallden-Abberton, Michael,Engelman, Carl,Fraenkel, Gideon
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p. 538 - 546
(2007/10/02)
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