- Redistribution equilibria of substituents between the methyl- and trimethylsilicon moieties
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Scrambling equilibria resulting from the exchange of pairs of monofunctional substituents (halogen, methoxyl, methylthio, and dimethylamino) between the methyl- and trimethylsilicon moieties have been studied by proton nuclear magnetic resonance. Unexpect
- Moedritzer, Kurt,Van Wazer, John R.
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- N-H cleavage as a route to new pincer complexes of high-valent rhenium
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A novel PNN-type pincer ligand has been accessed via imine reduction with LiAlH4 to provide the phosphine diamino proligand, PNHNH (1). The ligand, 1, as well as PNHP can be metallated directly, via N-H cleavage, with L2ReOX2(OEt) precursors to access six-coordinate (PNP)ReOCl2 (2) and (PNNH)ReOX2 (3-Cl, X = Cl; 3-Br, X = Br) in good yield. 3-Cl and 3-Br undergo dehydrohalogenation upon treatment with NEt3, furnishing the five-coordinate phosphine/diamido PNN-type compounds (PNN)ReOX (4-Cl, X = Cl; 4-Br, X = Br) in excellent yield, presenting as a mixture of rotameric diasteromers. The reversibility of this deprotonation, and the coordinative unsaturation of 4-Cl is shown in reactions with HCl(aq) and PMe3 providing 3-Cl and 4-PMe3, respectively. Treatment of 4-Cl with AgOAc, AgOTf, or NaHBEt3 lead to formation of (PNN)ReO(OAc) (4-OAc), (PNN)ReO(OTf) (4-OTf), and (PNN)ReO(H) (4-H), all isolated in excellent yields in varying diasteromeric ratios. The nature of the isomerism was analyzed based on solid-state structural studies and solution NMR data.
- Kosanovich, Alex J.,Shih, Wei-Chun,Ramírez-Contreras, Rodrigo,Ozerov, Oleg. V.
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- The First Gallium-Arsenic Compound containing a Single Ga3As Unit: Isolation and Crystal Structure of 3As (thf=tetrahydrofuran)
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3As (thf=tetrahydrofuran), isolated from the products of the reaction of (Me3Si)3As with GaBr3, has been shown by X-ray crystallographic analysis to be the first example of a compound containing a single Ga3As unit.
- Wells, Richard L.,Shafieezad, Soheila,McPhail, Andrew T.,Pitt, Colin G.
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- STEPWISE CONVERSION OF OXIRANES TO ALLYLIC ALCOHOLS BY IODOTRIMETHYLSILANE AND DBU
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Iodotrimethylsilane, prepared from hexamethyldisilane and iodine, reacts smoothly with oxiranes to give (2-iodoalkoxy)trimethylsilanes which can be converted to allylic alcohols with DBU in good yields.The whole conversion can be carried out in one-pot operation.
- Sakurai, Hideki,Sasaki, Koshi,Hosomi, Akira
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- A simple one-pot synthesis of methyltribromosilane
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A simple one-pot synthesis of methyltribromosilane has been developed. The straightforward reaction of a slight excess of silicon tetrabromide with one equivalent of powdered methyllithium in refluxing pentane produces methyltribromosilane in high yields.
- Pitcher, Michael W.,Bianconi, Patricia A.
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Read Online
- C3-Heteroaroyl cannabinoids as photolabeling ligands for the CB2 cannabinoid receptor
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A series of tricyclic cannabinoids incorporating a heteroaroyl group at C3 were prepared as probes to explore the binding site(s) of the CB1 and CB2 receptors. This relatively unexplored structural motif is shown to be CB2 selective with Ki values at low nanomolar concentrations when the heteroaromatic group is 3-benzothiophenyl (41) or 3-indolyl (50). When photoactivated, the lead compound 41 was shown to successfully label the CB2 receptor through covalent attachment at the active site while 50 failed to label. The benzothiophenone moiety may be a photoactivatable moiety suitable for selective labeling.
- Dixon, Darryl D.,Tius, Marcus A.,Thakur, Ganesh A.,Zhou, Han,Bowman, Anna L.,Shukla, Vidyanand G.,Peng, Yan,Makriyannis, Alexandros
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supporting information; experimental part
p. 5322 - 5325
(2012/09/07)
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- Homolytic reactions of N-bromohexamethyldisilazane with trialkyl(phenylalkoxy) derivatives of silicon and tin
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The main product of the photoinduced reaction of N- bromohexamethyldisilazane with trialkyl-(benzyloxy)derivatives of silicon and tin R3MO(CH2)nPh (R = Me, Et; M = Si, Sn; n = 1) is N,N-dibenzylidene-C-phenylmethanediamine (hydrobenzamide). For M = Si, with increase of the length of the methylene chain between the oxygen atom and the phenyl group (n = 2, 3), the similar reaction affords the product of bromination of the benzylic carbon atom R3MO(CH2) n-1CHBrPh. For M = Sn, the reaction results in the formation of 2-phenyloxacycloalkanes PhCHO(CH2)n-1. Pleiades Publishing, Ltd., 2010.
- Rakhlin,Podgorbunskaya,Voronkov
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experimental part
p. 930 - 935
(2011/01/09)
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- An efficient large-scale synthesis of gemcitabine employing a crystalline 2, 2-difluoro-α-ribofuranosyl bromide
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An efficient large-scale synthesis of gemcitabine was achieved without chromatography or fractional crystallization. The key steps include stereospecific conversion of a novel β-ribofuranosyl phosphate into a highly crystalline a-ribofuranosyl bromide and coupling of the α-ribofuranosyl bromide and trime- thylsilyl cytosine to produce a β-nucleoside. p-Phenylbenzoyl group was introduced for the protection of one of hydroxy groups in order to enhance the crystallinity of intermediates. Continuous removal of trimethylsilyl bromide, generated during the coupling reaction, by distillation from the reaction medium substantially enhanced the β-selectivity of the crucial coupling reaction.
- Chang, Young-Kil,Lee, Jaeheon,Park, Gha-Seung,Lee, Moonsub,Park, Chul Hyun,Kim, Han Kyong,Lee, Gwansun,Lee, Bo-Young,Baek, Ju Yuel,Kim, Kwan Soo
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experimental part
p. 5687 - 5691
(2010/09/18)
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- Structural chemistry of borazines
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The solid-state structure of (HN=BF)3 has been redetermined. It is characterised by a stacking of the molecules, similar to hexagonal boron nitride. In contrast, (F3CH2N=BF)3 shows no intermolecular interactions between the planar borazine rings. In (Cl 2BN=BCl)3, the Cl2B groups are almost perpendicularly oriented to the planar borazine ring and its B-Cl bonds are shorter than the Cl-B bonds to the ring boron atoms. Reactions of (Cl 2BN=BCl)3 with Me3SiNMe2 allows a successive Cl/Me2N exchange. Depending on the molar ratio, the compounds [Cl(Me2N)BN=BCl]3, [(Me2N) 2BN=BCl]3 and [(Me2N)2BN=BNMe 2]3 are obtained. The latter two react with CH 2Cl2 by B-N bond cleavage of one ring boron bonded Me 2N group with formation of an N-H bond. These molecules not only possess a strongly distorted BN hexagon with short B-NH bonds but also a nonplanar borazine ring. The nonplanarity of the borazine ring is even more pronounced in [Me3SiN=BCl]3. A planar borazine ring is observed for (MeN=BBr)3. Its molecules are ordered into stacks by translation with borazine planes 4.2 A apart from each other. Characteristic of the structure are close contacts between neighbouring bromine atoms. Due to the steric demand of pentafluorophenyl groups, the borazine ring of (F5C6N=BBr)3 forms no stacks because one of the three F5C6 rings stands almost perpendicular to the borazine plane while the other two are twisted by 70°. Aminolysis of (F 5C6N=BBr)3 yields (F5C 6N=BNH2)3 with NH2 groups that are coplanar with the borazine ring. The phenyl groups of (HN=BPh)3 are twisted by only 30-40° relative to the borazine ring. A threefold crystallographic axis stands perpendicular to the ring plane. The sixfold crystallographic axis of the unit cell generates a channel structure with an internal diameter of 4.5 A. The two isomeric borazines, (iPrN=BMe) 3 and (MeN=BiPr)3 are structurally rather similar although the first of these has longer B-N bonds due to the shorter N-C bonds. Moreover, the B-N-B and N-B-N bond angles are slightly different. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Anand, Benadir,Noeth, Heinrich,Schwenk-Kircher, Holger,Troll, Alexander
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experimental part
p. 3186 - 3199
(2009/02/07)
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- A convenient one-pot preparation of stable equivalents of cyclobutane-1,2-dione and cyclobutanetrione
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A very short, high-yielding, one-pot procedure has been developed for the preparation of half-protected cyclobutane-1,2-dione. This compound is much more stable than cyclobutane-1,2-dione itself and allowed further transformation to give diprotected cyclobutanetrione equivalents. Copyright Taylor & Francis Group, LLC.
- Deguest, Geoffrey,Bischoff, Laurent,Fruit, Corinne,Marsais, Francis
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p. 841 - 847
(2008/09/17)
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- Spin chemistry of organometallic compounds 5. Interaction of N-bromohexamethyl disilazane with substituted silyl hydrides
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Reaction of N-bromohexamethyl disilazane (Me3Si)2NBr with substituted triorganyl silanes R1R2R3SiH results in asymmetric disilazanes Me3SiNHSiR1R2R3 and bromination product, bromotrimethyl silane Me3SiBr. The reaction has demonstrated an unusual dependence on specific solvation. In benzene, bromination occurs immediately after mixing of the reagents, while in cyclohexane, the reaction products are formed only under UV-irradiation. Application of photoinduced CIDNP method has shown that the mechanism of bromination of triorganyl silanes is comprised of a series of consecutive radical stages involving N-centered disilazanyl (Me3Si)2N{radical dot} and Si-centered silyl R1R2R3Si{radical dot} radicals.
- Taraban, Marc B.,Rakhlin, Vladimir I.,Volkova, Olga S.,Podgorbunskaya, Tatyana A.,Kuibida, Leonid V.,Mirskov, Rudolf G.,Leshina, Tatyana V.,Sherstyannikova, Larisa V.,Voronkov, Mikhail G.
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scheme or table
p. 3815 - 3820
(2009/04/06)
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- Fully fluorinated imidodiphosphinate shells for visible- and NIR-emitting lanthanides: Hitherto unexpected effects of sensitizer fluorination on lanthanide emission properties
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In this paper we demonstrate that the effect of aromatic C - F substitution in ligands does not always abide by conventional wisdom for ligand design to enhance sensitisation for visible lanthanide emission, in contrast with NIR emission for which the same effect coupled with shell formation leads to unprecedented long luminescence lifetimes. We have chosen an imidodiphosphinate ligand, N-{P,P-di-(pentafluorophinoyl)}-P,P-dipentafluoro-phenylphosphinimidic acid (HF20tpip), to form ideal fluorinated shells about all visible- and NIR-emitting lanthanides. The shell, formed by three ligands. comprises twelve fully fluorinated aryl sensitiser groups, yet no-high energy X - H vibrations that quench lanthanide emission. The synthesis, full characterisation including X-ray and NMR analysis as well as the photo-physical properties of the emissive complexes [Ln(F20tpip)3], in which Ln = Nd, Sm, Eu, Gd, Tb, Dy, Er, Yb, Y, Gd, are reported. The photophysical results contrast previous studies, in which fluorination of alkyl chains tends to lead to more emissive lanthanide complexes for both visible and NIR emission. Analysis of the fluorescence properties of the HF20tpip and [Gd-(F20tpip)3] reveals that there is a low-lying state at around 715 nm that is responsible for partially quenching of the signal of the visible emitting lanthanides and we attribute it to a π - σ* state. However, all visible emitting lanthanides have long lifetimes and unexpectedly the [Dy(F20tpip)3] complex shows a lifetime of 0.3 ms, indicating that the elimination of high-energy vibrations from the ligand framework is particularly favourable for Dy. The NIR emitting lanthanides show strong emission signals in powder and solution with unprecedented lifetimes. The luminescence lifetimes of [Nd(F20tpip)3], [Er(F20tpip)3] and [Yb(F20tpip)3] in deuteurated acetonitrile are 44, 741 and 1111 μs. The highest value observed for the [Yb(F20tpip)3] complex is more than half the value of the Yb ion radiative lifetime.
- Glover, Peter B.,Bassett, Andrew P.,Nockemann, Peter,Kariuki, Benson M.,Van Deun, Rik,Pikramenou, Zoe
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p. 6308 - 6320
(2008/02/13)
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- Catalytic cleavage of phosphate ester bonds by boron chelates
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Novel chemical compounds are disclosed having the general formula L{YXm}n, wherein X is selected from the Group 13 elements, Y is a halide, and L is a chelating ligand containing at least one binding atom contacting the Group 13 element, the atom being selected from the group consisting of C, N, O, and S, and m and n are integers having a value of at least 1. L may be a Schiff base type ligand, such as a salen ligand. The compositions of the present invention may be bidentate, quadridentate, or greater. The compositions may be used in dealkylation of phosphate esters or ethers. Advantageously, the methods of the present invention may be rendered catalytic.
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Page/Page column 5-8
(2008/06/13)
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- Method for the Preparation of 2'-Deoxy-2',2'-Difluorocytidine
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This invention relates to an improved method for stereoselectively preparing 2¢¥-deoxy-2¢¥,2¢¥-difluorocytidine of formula (I), which comprises the steps of reacting a 1-halo ribofuranose compound of formula (III) with a nucleobase of formula (IV) in a solvent to obtain a nucleoside of formula (II) with removing the silyl halide of formula (V) produced during the reaction; and deprotecting the nucleoside of formula (II) to obtain 2¢¥-deoxy-2¢¥,2¢¥-difluorocytidine of formula (I).
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Page/Page column 8
(2008/06/13)
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- Reactions of N-bromohexamethyldisilazane with triorganylsilanes
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Reactions of N-bromohexamethyldisilazane (Me3Si)2NBr with Si-H compounds of the general formula RR'2SiH yield up to 90% of unsymmetrical disilazanes (Me3Si)2NSiRR2 and bromotrimethylsilane. An unexpected solvent effect on the reaction conditions is revealed: In benzene the products are formed already on mixing, whereas in cyclohexane, under UV irradiation only. Nauka/Interperiodica 2006.
- Rakhlin,Podgorbunskaya,Mirskov,Voronkov,Gendin
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p. 1562 - 1563
(2008/02/07)
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- A new route to organoboron polymers via highly selective polymer modification reactions
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We have developed a highly efficient new method for the introduction of Lewis acidic boron centers into the side chains of organic polymers. Our methodology involves three steps: (i) the controlled polymerization of the functional monomer 4-trimethylsilylstyrene (S-Si), (ii) the exchange of the silyl groups in poly(4-trimethylsilylstyrene) (PS-Si) with BBr3 to give the reactive polymer poly(4-dibro-moborylstyrene) (PS-BBr), and (iii) the fine-tuning of the Lewis acidity of the individual boron centers through substituent exchange reactions with nucleophiles. Treatment of PS-BBr with ethoxytrimethylsilane and THF respectively yields the moderately Lewis acidic poly(arylboronate)s PS-BOR (R = Et, 4-bromobutyl). The alkoxy groups in PS-BOR have been exchanged with pinacol to form the air-stable polymer PS-BPin (Pin = pinacolato). Treatment of PS-BBr with 2-thienyltrimethyltin and pentafluo-rophenylcopper respectively gives the well-defined highly Lewis acidic triarylborane polymers PS-BTh and PS-BPf (Th = 2-thienyl, Pf = 2,3,4,5,6-pentafluorophenyl), which contain triarylborane moieties at every repeat unit along the polymer chain. All polymers have been studied by multinuclear NMR spectroscopy and differential scanning calorimetry. The molecular weights of the arylboronate polymers PS-BOR have been determined by gel permeation chromatography, and the highly selective formation of polymer PS-BPin has been confirmed by static light scattering.
- Qin, Yang,Cheng, Guanglou,Achara, Obianuju,Parab, Kshitij,Jaekle, Frieder
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p. 7123 - 7131
(2007/10/03)
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- Spin chemistry of organometallic compounds. 2. Interaction of N-bromohexamethyldisilazane with allyltriorganolsilanes
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Two instances have been considered demonstrating the influence of organoelement substituent on the reactivity of radicals generated from R3MCH2CH=CH2 (M = Si or Sn) in photoinduced interaction with (Me3Si)2
- Taraban, Marc B.,Kruppa, Alexander I.,Polyakov, Nikolai E.,Voronkov, Mikhail G.,Rakhlin, Vladimir I.,Grigor'ev, Stanislav V.,Volkova, Olga S.,Mirskov, Rudolph G.,Leshina, Tatyana V.
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p. 228 - 234
(2007/10/03)
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- Process for producing novel naphthyridine derivatives
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A novel naphthyridine derivative showing high activity as a tachykinin receptor antagonist can be produced at high efficiency by reacting an acylating agent such as a carboxylic acid derivative with a compound represented by the formula (1): wherein R1, R2 and R3 represent independently a hydrogen atom, a lower alkyl group, a lower alkoxyl group, an aryl group, a heteroaryl group, an amino group, etc., and X1 and X2 represent respectively a halogen atom.
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- Reactions of methyl(pentafluorophenyl)- and methyl(pentafluorophenyl)phenylsilanes with electrophiles. A convenient preparative route to halogeno(methyl)pentafluorophenylsilanes C6F5SiMe2X and C6F5SiMeX2 (X=F, Cl and Br)
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Halogeno(methyl)pentafluorophenylsilanes C6F5SiMenX3-n (n=1, 2) (X=F, Cl, Br) were prepared in good yields from the corresponding phenylsilanes C6F5SiMenPh3-n by reactions with the electrophiles aHF, HCl-AlCl3, Br2-AlBr3 or AlX3 (X=Cl, Br) halogenated hydrocarbons. Additionally, reactions of C6F5SiMe3 and (C6F5)2SiMe2 with selected electrophiles were studied.
- Frohn,Lewin,Bardin
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p. 255 - 263
(2007/10/03)
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- Synthesis of vinylphosphinoyl derivatives. Triethyl orthoformate as a new dehydrohalogenating agent
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Trimethyl and triethyl orthoformates are proposed as new dehydrohalogenating agents. They are used for synthesis of vinylphosphinoyl compounds.
- Kurdyumova,Ragulin,Tsvetkov
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p. 750 - 752
(2007/10/03)
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- The CuBr/Fe0 promoted radical addition of methyl 2-Br-2-Cl-carboxylates to olefins
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Methyl 2-Br-2-Cl-carboxylates afford 2-alkyl-2-Cl-4-Br-carboxylates in fair yields by reaction with terminal alkenes, under mild conditions, through a radical process promoted by CuBr/Fe0 in DMF/CH2Cl2.
- Forti, Luca,Ghelfi, Franco,Lancellotti, Massimiliano Lodi,Pagnoni, Ugo M.
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p. 1699 - 1710
(2007/10/03)
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- Carbocyclic nucleosides containing bicycle rings, oligonucleotides therefrom, process for their preparation, their use and intermediates
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Compounds of the formulae I and Ia and their racemates STR1 in which A is --CH2 -- or --CH2 CH2 --, R1 is hydrogen or a protective group, R2 is hydrogen or a protective group or a radical forming a phosphorus-containing nucleotide bridge group and B is a purine or pyrimidine radical or an analogue thereof, can be used as antiviral active ingredients or for the preparation of biologically active oligonucleotides.
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- DIALKYL(TRIMETHYLSILYL)TETRATHIOPHOSPHATES IN SYNTHESIS OF SUBSTITUTED TETRATHIOPHOSPHATES
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Reactions of S,S'-dialkyl-S''-trimethylsilyl tetrathiophosphates with aldehydes, acetals, ortho ethers, aminals, thioacetals, bis(thiocyanato)methane, disulfides and alkyl halides resulted in the products of tetrathiophosphate structure.Key words: S,S'-Dialkyl-S''-trimethylsilyl tetrathiophosphates; organic substances; substituted tetrathiophosphates.
- Nizamov, Il'Yas S.,Kuznetzov, Vladislav A.,Batyeva, Elvira S.
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p. 249 - 258
(2007/10/02)
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- DIALKYL TRIMETHYLSILYL TETRATHIOPHOSPHATES. SYNTHESIS AND TRANSFORMATIONS
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We have developed an efficient method for synthesizing dialkyl trimethylsilyl tetrathiophosphates, which react with aldehydes, acetals, ortho esters, thioacetals, bis(thiocyanato)methane, diethyl disulfide, and alkyl halides to give a number of new tetrathiophosphate derivatives.
- Nizamov, I.S.,Kuznetsov, V.A.,Batyeva, E.S.,Al'fonsov, V.A.
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p. 1196 - 1198
(2007/10/02)
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- REACTION OF DIALKYLDITHIOTRIMETHYLSILYLPHOSPHITES WITH ACYL HALIDES
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It has been established that S,S-dialkyltrimethylsilyldithiophosphites react with acyl halides in two directions, depending on the nature of the halogen in the acyl halide and on the reaction conditions, thus giving as the main reactions products either dialkyldithiohalophosphites or dialkyldithioacylphosphonates.The latter compounds react with acyl halides in accordance with retro-Arbuzov reaction scheme, giving dialkyldithiohalophosphites. Keywords: dialkyldithiotrimethylsilylphosphites, acyl halides, dialkyldithioacylphosphites, dialkyldithioacylphosphonates.
- Al'fonsov, V. A.,Trusenev, A. G.,Gainullin, R. M.,Batyeva, E. S.,Pudovik, A. N.
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p. 799 - 803
(2007/10/02)
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- REACTIONS OF N-SILYLATED LACTAMS WITH α-BROMO CARBOXYLATES
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The reactions of N-trimethylsilyl lactams with α-bromo carboxylates proceeds in two directions: the N-alkylation of the lactams, and elimination with the formation of α,β-unsaturated carboxylic esters.The proportion between the two processes depends on the structure of the initial compounds.
- Orlova, N. A.,Shipov, A. G.,Baukov, Yu. I.
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p. 1877 - 1880
(2007/10/02)
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- INTRA- AND INTER-MOLECULAR REACTIONS OF ALKYL THIOCYANATES WITH DERIVATIVES OF P(III) ACIDS IN PRESENCE OF CHLORIDE ION DONORS
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By the reaction of 2-(trimethylsiloxy) thiocyanate with phosphorus trichloride we synthesized 2-thiocyanatoethyl phosphorodichloridite, which under the action of dialkylamines or (dialkylamino)trimethylsilanes is converted into S-(2-chloroethyl) tetraalkylphosphorodiamidothioates.The reactions of ethyl thiocyanate with tributyl phosphite and butyl tetraethylphosphorodiamidite in presence of chlorotrimethylsilane give O,O-dibutyl S-ethyl phosphorothioite or S-ethyl tetraethylphosphorodiamidite, cyanotrimethylsilane, and butyl chloride.In the reaction of ethyl thiocyanate with hexaethylphosphorous triamide and chlorotrimethylsilane hexaethylphosphorothioic triamide, cyanotrimethylsilane, and ethyl chloride are formed.
- Kamalov, R. M.,Stepanov, G. S.,Ryzhikov, D. V.,Pudovik, M. A.,Pudovik, A. N.
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p. 1614 - 1619
(2007/10/02)
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- Standard Enthalpy of Formation of Hexamethyldisilane
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The standard (p0 = 0.1 MPa) enthalpy of formation at 298.15 K of liquid hexamethyldisilane was determined by measuring the enthalpy of its reaction with bromine to produce trimethylsilicon bromide.The required ΔfH0m/kJ mol-1 = -330.4 +/- 2.7 was determined from its enthalpy of hydrolysis in aqueous hydrobromic acid.The final result, ΔfH0m/kJ mol-1 = -341.1 +/- 5.5 differs considerably from previous determinations and the consequences for the thermochemistry of silicon-methyl species are discussed.In particular the enthalpies of formation of the silylenes, SiH2, SiHMe and SiMe2, were derived as 266, 201 and 140 kJ mol-1, respectively, with uncertainties -1.
- Pilcher, Geoffrey,Leitao, M. Luisa P.,Meng-Yan, Yang,Walsh, Robin
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p. 841 - 845
(2007/10/02)
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- An improved preparation of enamines of acylsilanes, a new synthesis of acylsilanes
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The use as solvent of hexamethylphosphortriamide instead of the previously used tetrahydrofuran has allowed the synthesis in high yield of enamines of acylsilanes (2) from cyanohydrins (1) by reductive silylation with Me3SiCl/Li.Protodesilylation of 2a (R = R' = Me) by HCl has in dry diethyl ether or by trimethylchlorosilane in methanol gave, after neutralization, a quantitative yield of the enamine Me2C=C(SiMe3)NH2, which was surprisingly stable.Its ready hydrolysis to the corresponding acylsilane provided a new route to this type of compound.Reaction of bromine with 2a gave α-bromoisobutyronitrile.
- Picard, J. P.,Aizpurua, J. M.,Elyusufi, A.,Kowalski, P.
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- Synthesis and characterization of four-membered gallium-arsenic ring compounds containing a bridging As(SiMe3)2 group: crystal structures of and
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The first organogallium four-membered ring compounds with arsenic, halogen mixed bridging to be characterized completely, Ph2(X = Cl (1) and X = Br (2) were prepared by the reaction of (Me3Si)3As (3) with Ph2GaCl and Ph2GaBr, respectively.X-ray crystallographic analyses show the compounds to be isostructural with each containing a non-planar Ga-As-Ga-X four membered ring.Isomorphous crystals of 1 and 2 belong to the monoclinic system, space group P21/c (C52h), with four molecules in unit cells of dimensions: a 10.560(3), b 15.797(3), c 20.591(4) Angstroem, β 92.17(2) deg, V 3433(2) Angstroem3 for 1, and a 10.653(1), b 15.777(2), c 20.517(2) Angstroem, β 91.97(1) deg, V 3446(1) Angstroem3 for 2.The non-planarity of the rings is manifested in the halogen atom displacements of 0.256 Angstroem in 1 and 0.293 Angstroem in 2 from the respective Ga-As-Ga' planes.Deviations from overall C2y symmetry serve to relieve unfavorable intramolecular bulky ring substituent interaction present in such a symmetric form.The dimer 2 (4), obtained from the reaction of Ph2GaCl and LiAs(SiMe3)2, has been characterized by partial elemental analysis, NMR spectroscopy and cryoscopic molecular weight determination.An alternative route to the synthesis of 1 by reaction of 4 and Ph2GaCl was investigated via NMR spectroscopy.
- Holley, William K.,Wells, Richard L.,Shafieezad, Soheila,McPhail, Andrew T.,Pitt, Colin G.
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- Triazaboles and related triazole derivatives of boron
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The reaction of trimethylamine-borane, Me3N·BH3, with 1,2,4-triazole (=Hst) results in the formation of an oligomer mixture of the composition [H2B(st)]n; species with n up to 6 could be identified by mass spectrometry. Dimeric species = sym-triazaboles, R2B(μ-st)2BR2 (2, R = hydrocarbon group), can be obtained in low yield from the condensation of R3B with Hst, from the interaction of halodiorganylboranes, R2BX (X = Cl, Br), with N-(trimethylsilyl)-1,2,4-triazole, Me3Si(st), and also by a transamination of a (dimethylamino)diorganylborane, Me2NBR2, with Hst. However, the major products are generally oligomeric materials [R2B(st)]n. The interaction of 3-amino-1,2,4-triazole (=Hat) with excess of R3B ultimately gives a reasonable yield of a mixture of two isomeric triazaboles of type 2 with the amino groups in either the 1,5- or 1,7-positions, whereas transamination of Me2NBR2 with Hat preferentially gives the 1,5-diamino isomer but in low yield. Several boron derivatives of 1,2,3-triazoles have been isolated and characterized; these include tetrameric species (derived from 1,2,3-triazole = Hut or benzotriazole = Hbt) with a cyclic structure (6) resembling that of porphine, but also oligomeric materials [R2B(ut)]n and [R2B(bt)]n.
- Niedenzu,Woodrum
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p. 4022 - 4026
(2008/10/08)
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- Aminoiminoboranes as Synthons for the Preparation of Three- and Four-Membered Rings with the Ring-Atom Sequence BNE, BNBE, BNSiE, and NBNE (E = P, Partly also B, Si, Ge, As)
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Dihalides AHal2 add to the iminoborane iPr2NBNtBu (1a) to give diaminoboranes iPr2NB(Hal)N(tBu)-AHal (2a-i) and the triaminoborane (iPr2N)2BN(tBu)-AsBr2 (2j); by the substitution of Hal by NiPr2 or Me in 2e, f, j the derivatives 2k-m are formed.With the aid of alkali metal, the diaminoboranes 2a, c, d, m are dehalogenated to the three-membered ring compounds N(tBu)-A-> with A = B(NiPr2) (3), SiR2 (4a, b), P(NiPr)2 (5), whereas the dechlorination of 2a, c with Li2EPh (E = P, As) yields the four-membered ring products N(tBu)-A-E(Ph)-> with A = B(NiPr2) (6, 7), SiMe2 (8, 9).Dichlorides ACl2 are added to the iminoborane Me3Si(tBu)NBNtBu (1b) to give either the diaminoboranes Me3Si(tBu)NB(Cl)N(tBu)-ACl (2n-w) or the four-membered rings B(Cl)N(tBu)-A-> with A = GeMe2 (12), PX (13a-e), AsCl (14a), Me3SiCl being a second product.The same type of ring compound with A = BX (10a-d), SiX2 (11a, b) is formed from 2n-s during the elimination of Me3SiCl by the action of the solvent chloroform at room temperature.The Cl atom in these ring compounds can be substituted by alkyl, amino, or alkoxy groups to give 10e, f, 13f-h, 14b-j.The configuration and conformation of the products in solution and the structure of 3, 6, 7, 12, 14b in the solid state are discussed on the basis of NMR and X-ray data, respectively.
- Bonn, Karl-Heinz van,Schreyer, Peter,Paetzold, Peter,Boese, Roland
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p. 1045 - 1058
(2007/10/02)
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- (C5Me5)SiMe3 as a mild and effective reagent for transfer of the C5Me5 ring: an improved route to monopentamethylcyclopentadienyl trihalides of the group 4 elements
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The reaction between (C5Me5)SiMe3 and group 4 element tetrahalides MX4 (M=Ti, X=Cl, Br, I; M=Zr and Hf, X=Cl) gives the corresponding (η5-C5Me5)MX3 derivatives in nearly quantitative yields in a one-step procedure without the need for further purification.
- Llinas, Gerardo Hidalgo,Mena, Miguel,Palacios, Federico,Royo, Pascual,Serrano, Ricardo
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- NEW SYNTHESIS OF DIALKOXYTHIOXAPHOSPHORANESULFENYL BROMIDES AND CHLORIDES
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The synthesis of new pseudohalogen thioxaphosphoranesulfenyl bromides by simple bromination of bis(dialkoxythiophosphoryl)disulfides is presented.The new bromides turned out to be excellent thiophosphorylating agents, as well as substrates for a novel, highly efficient preparation of dialkoxythioxaphosphoranesulfenyl chlorides 4.
- Lopusinski, Andrzej,Potrzebowski, Marek
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- BEITRAG ZUR SYNTHESE VON ORGANYL-TRIMETHYLSILYL-SELENIDEN, R-Se-Si(CH3)3
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Phenyl-trimethyl-selenide and 2,4,6-trimethylphenyl-selenide have been synthesized and characterized from the organobromide, magnesium, selenium and trimethylchlorosilane.A better method has been found for the synthesis of organyl-trimethylsilyl-selenides.It starts from sodium-trimethylsilylselanolate, the synthesis of which is described.Its reactions with methylbromide, benzylbromide and n-pentylbromide result in the formation of the compounds R-Se-Si(CH3)3 with the corresponding groups R.Secundary as well as tertiary bromides do not react in the expected manner.
- Schmidt, Max,Kiewert, Eva,Lux, Horst,Sametschek, Cordula
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p. 163 - 168
(2007/10/02)
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- SILYL-NITROGEN COMPOUNDS I. REACTIONS OF DILITHIUM BIS(TRIMETHYLSILYLL)HYDRAZINE WITH GROUP IV HALIDES
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Dilithium 1,2-bis(trimethylsilyl)hydrazine (1) reacts with CCl4, Me3SiCCl3 and CBr4 to form predominantly bis(trimethylsilyl)aminocarbonimidic dichloride, bis(trimethylsilyl)aminoisocyanide and bis(trimethylsilyl)diazene, whereas similar reactions with HCCl3, HCI3, H2CCl2, H2CI2, C2H4Cl2 or C2H2Cl4 lead to increasing amounts of bis(trimethylsilyl)hydrazine.In addition to the hydrazone, (Me3Si)2N-N=CH(Cl), the reaction of 1 with CHCl3 forms a small amount of triazasilacyclopentane,.............. .In contrast, Me2SnCl2 reacts with 1 to give tetraazadistannacyclohexane (Me2Sn(NSiMe3)2)2, whereas SnCl4, SnCl2 and PbCl2 act mainly as oxidants and Me2SiCl2 forms polymers.Another product of the reaction of 1 with SnCl2 or PbCl2 is LiN(SiMe3)2 originating perhaps from LiNH(SiMe3) or (LiNN(SiMe3)2)2.
- Vasisht, Sham Kumar,Sood, Mohini,Sood, Nirupma,Singh, Gursharan
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- The Synthesis of α-Fluoroalkylphosphonates
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A general synthesis of functionalized α-fluoroalkylphosphonates is provided by reaction of the dialkyl fluoromethylphosphonate carbanion with aldehydes, ketones, alkyl halides, silyl halides, and acyl halides.Further transformation of the primary products expands the scope of the synthetic method.
- Blackburn, G. Michael,Parratt, Martin J.
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p. 1425 - 1430
(2007/10/02)
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- A NEW CONVENIENT LABORATORY SYNTHESIS OF TRIMETHYLSILYL BROMIDE
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Trimethylsilyl bromide is prepared in a laboratory scale from trimethylsilyl 4-bromo 2-alkenoates in almost quantitative yield.
- Bellassoued, M.,Borgi, A. El,Gaudemar, M.
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p. 973 - 976
(2007/10/02)
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- Halophosphanes
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The phosphane 2, Me3SiO(CF3)2CPX1X2 (X1=X2=H), is converted in good yields by N-chloro- or N-bromosuccinimide into the phosphanes 3b (X1=H, X2=Cl), 3c (X1=H, X2=Br), 4b (X1=X2=Cl), and 4c (X1=X2=Br).Antimony trifluoride fluorinates 3c and 4c to give 3a (X1=H, X2=F) and 4a (X1=X1=F).The monobromophosphane 3c reacts with dimethylamine to yield the secondary aminophosphane 3e, with trimethylamine dehydrobromination takes place with formation of the diphosphene 5, characterized by its NMR spectra, and the cycloptriphosphane 6.The NMR spectra of the halophosphanes are discussed including the thermically labile iodophosphanes 3d (X1=H, X2=I) and 4d (X1=X2=I).
- Kischkel, Helmut,Roeschenthaler, Gerd-Volker
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p. 4842 - 4848
(2007/10/02)
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- SYNTHESIS OF α-HALO AND α-DEUTERIO β-LACTAMS
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A convenient synthesis of 3,3-dibromo-2-azetidinones involves the reaction of an imine with the trimethylsilyl ester of tribromoacetic acid and triphenylphosphine; reduction with n-Bu3SnH and n-Bu3SnD can be controlled to lead to cis-3-bromo-2-azetidinones, and cis or trans 3-deuterio-2-azetidinones.
- Manhas, M.S.,Khajavi, M.S.,Bari, S.S.,Bose, Ajay K.
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p. 2323 - 2326
(2007/10/02)
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- Transition Metal Substituted Phosphanes, Arsanes, and Stibanes, XXXIII. (Bromomethyl)bisarsane: Synthesis and Metalation to Complexes with η1- or η2-Coordinated Arsinomethyl Ligand
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The pyrolysis of the trialkyldibromoarsorane (Me3SiCH2)3AsBr2 (1) under reduced pressure yields the (bromomethyl)arsane (Me3SiCH2)2AsCH2Br (2) with Me3SiBr elimination via the intermediate formation of the bromodialkylmethylenearsorane Br(Me3SiCH2)2As=CH2. 2 reacts with Na (M = Mo, W) to give the transition metal substituted arsanes Cp(CO)3M-CH2As(CH2SiMe3)2 (3a,b).These undergo cyclisation with loss of CO and formation of Cp(CO)2M2-CH2As(CH2SiMe3)2> (4a,b), the first complexes with an η2-bound arsinomethyl unit, either spontaneously (3a) or upon ultraviolet irradiation or prolonged standing at room temperature (3b).MeI quaternizes the arsane 3b to give the metalated arsonium salt I (5).The NMR spectra indicate fluxional behaviour for the chiral metallacycles 4a,b.It is caused by a rapid change of the configuration at the metal centre, for which a mechanism, involving a rotation of the dihapto-coordinated ligand about an axis defined by the metal and the centre of the As-C(M) bond, is suggested.
- Meyer, Angelika,Hartl, Anna,Malisch, Wolfgang
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p. 348 - 359
(2007/10/02)
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- The Mechanism of the Reaction of Molecular Bromine with Organosilicon Hydrides
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The kinetics of the bromination of 7 triarylsilanes and 14 other organosilicon hydrides by molecular bromine in CCl4 have been determined by the stopped flow method.For triethylsilane, Arrhenius parameters have been measured in octane and CCl4, and solvent effects determined in other solvents of different polarity.The results accord with a molecular mechanism involving one molecule of bromine and one of the organosilicon hydride, with partial positive charge build-up on silicon in the transition state.
- El-Durini, Nabil M. K.,Jackson, Richard A.
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p. 1275 - 1278
(2007/10/02)
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- Interhalogen-Catalyzed Cleavages of Ethers and Esters with Trimethylsilyl Bromide or Chloride
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The cleavages of various dialkyl ethers, trimethylsilyl alkyl ethers, and alkyl esters by trimethylsilyl bromide are strongly catalyzed by iodine monobromide.This catalyzed cleavage procedure using iodine monobromide makes possible synthetic applications for trimethylsilyl bromide which were previously ruled out by problems with its low reactivity.Cleavages of benzylic and tertiary alkyl ethers and esters by trimethylsilyl chloride are feasible when catalyzed by iodine monochloride.However, other systems are essentially unreactive toward trimethylsilyl chloride even in the presence of iodine monochloride.
- Friedrich, Edwin C.,DeLucca, George
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p. 1678 - 1682
(2007/10/02)
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- REACTION OF TRIMETHYLSILYL AZIDE WITH ORGANIC HALIDES
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Trimethylsilyl azide reacted readily with benzyl, allyl, and aliphatic halides to give the corresponding azides in good to excellent yields.
- Nishiyama, Kozaburo,Karigomi, Hiroshi
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p. 1477 - 1478
(2007/10/02)
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