- CONVENIENT ONE-STEP SYNTHESES OF TRI-n-BUTYLTIN BROMIDE OR IODIDE AND DI-n-BUTYLTIN DIBROMIDE OR DIIODIDE FROM THE CORRESPONDING ORGANOTIN CHLORIDES
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Tri-n-butyltin bromide or iodide and di-n-butyltin dibromide or diiodide may be conveniently prepared from the corresponding organotin chlorides by tetra-n-butylammonium halide-catalyzed halogen redistribution reactions with suitable alkyl bromides or iod
- Friedrich, Edwin C.,Abma, Charles B.,Delucca, George
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- The Tris(pentafluoroethyl)stannate(II) Anion, [Sn(C2F5)3]?—Synthesis and Reactivity
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Syntheses of salts containing the tris(pentafluoroethyl)stannate(II) ion, [Sn(C2F5)3]?, were achieved through deprotonation of the corresponding stannane, HSn(C2F5)3, as well as
- Wiesemann, Markus,Kl?sener, Johannes,Niemann, Mark,Neumann, Beate,Stammler, Hans-Georg,Hoge, Berthold
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- Stannylation of Aryl Halides, Stille Cross-Coupling, and One-Pot, Two-Step Stannylation/Stille Cross-Coupling Reactions under Solvent-Free Conditions
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Solvent-free protocols for palladium-catalyzed stannylation of aryl halides, Stille cross-coupling, and one-pot, two-step stannylation/Stille cross-coupling (SSC) are reported for the first time. (Het)aryl halides bearing acceptor, donor, as well as sterically demanding substituents are stannylated and/or coupled in high yields. The reactions are catalyzed by conventional palladium(II) acetate/PCy3 [Pd(OAc)2/PCy3] under air, using available base CsF, and without the use of high purity reagents. The developed synthetic procedures are versatile, robust, and easily scalable. The absence of solvent, and the elimination of isolation procedures of aryl stannanes makes the SSC protocol simple, step economical, and highly efficient for the synthesis of biaryls in a one-pot two-step procedure.
- Gribanov, Pavel S.,Golenko, Yulia D.,Topchiy, Maxim A.,Minaeva, Lidiya I.,Asachenko, Andrey F.,Nechaev, Mikhail S.
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supporting information
p. 120 - 125
(2018/01/17)
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- GaBr3-catalyzed Coupling between α-Iodo Esters with Alkynylstannanes under UV Irradiation
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A coupling between various alkynylstannanes with α-iodo esters was catalyzed by GaBr3 under UV irradiation conditions, for which a catalytic amount of GaBr3 was essential, and a radical coupling with the generated alkynylgallium species was involved. The desired α-alkynyl esters were selectively obtained even in the presence of an aryl-I bond, which is a reactive site in a conventional palladium-catalyzed system.
- Suzuki, Itaru,Esumi, Naoto,Yasuda, Makoto,Baba, Akio
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- Sonochemical synthesis of bis(tri-n-butylstannyl) aromatic compounds via Barbier-like reactions
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This paper reports a study of the synthesis of aryltri-n-butylstannanes via a sonochemical Barbier reaction of aryl- and heteroaryl bromides with bis(tri-n-butyltin) oxide (2) in THF. Our results demonstrate that, despite previous reports on contrary, the aryltributylstannanes can also be obtained under the same reaction conditions via sonicated reactions between aryl monobromides and tri-nbutyltin chloride (2). A comparative study of the reactions of electrophiles 2 and 3 with bromobenzene, 2-bromopyridin, o- and m-bromoanisole, m-bromotoluene, 9-bromophenthrene, and 9-bromoanthracene, indicates that the corresponding aryl- and heteroaryl-tri-n-butylstannyl derivatives are obtained in about the sameyields. Best reaction conditions and the results obtained in the investigation of the sonicated reactions between several aromatic and heteroaromatic dibromides are also reported. It was found that the reactions using 1,2-, 1,3-, and 1,4-dibromobenzenes, 4,40-dibromobiphenyl, 1,4-dibromonaphthalene, 2,5-and 3,5-dibromopyridines, and 2,5-dibromothiophene lead to the corresponding bis(tri-n-butylstannylated) derivatives in many cases in very high yields. Also the excellent results obtained in the sonicated reactions of 1,3,5-tribromobenzene with 2 and 3 are reported.
- Gerbino, Darío C.,Fidelibus, Pablo M.,Mandolesi, Sandra D.,Ocampo, Romina A.,Scoccia, Jimena,Podestá, Julio C.
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- Stereoselective hydrostannation of substituted alkynes initiated by triethylborane and reactivity of bulky triorganotin hydrides
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This paper reports the results obtained in a study on the radical hydrostannation of mono- and disubstituted alkynes with bulky triorganotin hydrides using triethylborane as initiator. The addition of trineophyl- (1), tris[(phenyldimethylsilyl)methyl]- (2), and 9-tripticyldimethyltin (3) hydride to eight alkynes was carried out at room temperature leading to vinylstannanes in good to excellent yields and, mostly, with complete stereoselectivity. The results obtained in a study on the relative reactivity of trineophyl- (1), tris[(phenyldimethylsilyl)methyl]- (2), 9-triptycyldimethyltin (3) hydrides, and tri-n-butyltin hydride (29) using the radical reactions between these hydrides and 6-bromo-1-hexene (28) are also reported. Full 1H-, 13C-, and 119Sn NMR characteristics are included.
- Faraoni, María B.,Dodero, Verónica I.,Koll, Liliana C.,Zú?iga, Adriana E.,Mitchell, Terence N.,Podestá, Julio C.
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p. 1085 - 1091
(2007/10/03)
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- Weaker lewis acid, better catalytic activity: Dual mechanisms in perfluoroarylborane-catalyzed allylstannation reactions
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(Matrix is presented) PhB(C6F5)2 exhibits much higher activity as a Lewis acid catalyst for the allylstannation of aromatic aldehydes than the stronger Lewis acid B(C6F 5)3. This anomalous enhancement of catalytic activity for the weaker LA is shown to be partly due to decreased thermodynamic stability of ion pair 2b relative to 2a in the product-forming step of the reaction. A mechanistic path where the borane serves as the true LA catalyst is more important for the weakly Lewis acidic borane.
- Morrison, Darryl J.,Piers, Warren E.
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p. 2857 - 2860
(2007/10/03)
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- Synthesis, structure and catalytic application of palladium(II) complexes bearing N-heterocyclic carbenes and phosphines
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A variety of mixed palladium(II) complexes bearing N-heterocyclic carbenes (NHCs) and triaryl- and trialkylphosphines [NHC(R2)]Pd(PR′3)I2 (R=Me, t-Bu, (R)-1-phenylethyl; R′=Ph, o-tolyl, cyclohexyl, t-Bu) have been prepared. Crystal structure details of trans-diiodo(1,3-di-tert-butylimidazolin-2-ylidene)(triphenylphosphino) palladium(II) are presented. The complexes were tested as catalysts in the Mizoroki-Heck, Suzuki-Miyaura and Stille reactions as well as in the dimerization of phenylacetylene. In catalytic studies of the Suzuki-Miyaura cross-coupling reaction, the performance of these novel complexes was compared to the results obtained by the corresponding bis(NHC) and bis(phosphine) complexes.
- Herrmann, Wolfgang A.,B?hm, Volker P.W.,Gst?ttmayr, Christian W.K.,Grosche, Manja,Reisinger, Claus-Peter,Weskamp, Thomas
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p. 616 - 628
(2007/10/03)
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- Palladium complex-catalyzed germylation of allylic halides using (germyl)stannanes
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(Triethylgermyl)tributylstannane reacts metal-selectively with allylic halides at room temperature (r.t.) in the presence of tris(dibenzylideneacetone)dipalladium, Pd2(dba)3CHCl3, to provide an alternative route to allylge
- Nakano, Taichi,Ono, Kazuyoshi,Senda, Yoshiya,Migita, Toshihiko
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p. 313 - 317
(2007/10/03)
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- Easy general method for interhalide conversions in organotin compounds
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The halides in organotin halides are easily interconverted in excellent yields using aqueous ammonium halide solutions and various organic solvents.
- Zobel, Bernhard,Lim, Allan E. K.,Dunn, Kerri,Dakternieks, Dainis
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p. 4889 - 4890
(2008/10/08)
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- Diverging effects of steric congestion on the reaction of tributylstannyl radicals with areneselenols and aryl bromides and their mechanistic implications
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The effects of bulky ortho,ortho' groups on the reactions of aryl bromides and areneselenols with tributylstannane have been studied. Bulky ortho,ortho' groups accelerate the reaction of the bromides with the stannane but retard the reactions of the selenols. On the other hand, ab initio and force field calculations show that introducing bulky ortho substituents into selenols causes a greater increase in strain than in the corresponding bromides. Two possible explanations for the divergent reactivity patterns are advanced. On one hand, it is possible that bromine abstraction by stannyl radicals from aryl bromides proceeds in a single step through a linear transition state whereas the abstraction of sell from the selenols involves a T-shaped, hypervalent intermediate. Alternatively, it may be that both reactions are concerted with the bromine abstraction having a late transition state and the sell abstraction an early one. Approximate second-order rate constants for the reaction of tributylstannane with a range of hindered aryl bromides are derived from competition reactions. 2,4,6-Tri-tert- butylbenzeneselenol is able to function moderately well as a catalyst for the stannane-mediated reactions of vinyl bromides. The X-ray crystal structure of bis(2,4,6-triisopropylphenyl) diselenide is presented.
- Crich, David,Hwang, Jae-Taeg,Gastaldi, Stephane,Recupero, Francesco,Wink, Donald J.
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p. 2877 - 2882
(2007/10/03)
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- Mechanism of the Stille reaction. 1. The transmetalation step. Coupling of R1I and R2SnBu3 catalyzed by trans-[PdR1IL2] (R1 = C6Cl2F3; R2 = vinyl, 4-methoxyphenyl; L = AsPh3)
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The so far accepted mechanism of the Stille reaction (palladium- catalyzed cross-coupling of organotin reagents with organic electrophiles) is criticized. Based on kinetic studies on catalytic reactions, and on reactions with isolated intermediates, a corrected mechanism is proposed. The couplings between R1I (1) (R1 = C6-Cl2F3 = 3,5-dichlorotrifluorophenyl) and R2SnBu3 (R2 = CH=CH2, 2a; C6H4-4-OCH3, 2b), catalyzed by trans- [PdR1I(AsPh3)2] (3a), give R1-R2 and obey a first-order law, r(obs) = a[3a][2a]/(b + [AsPh3]), with a = (2.31 ± 0.09) x 10-5 s-1 and b = (6.9 ± 0.3) x 10-4 mol L-1, for [1] = [2a] = 0-0.2 mol L-1, [3a] = 0-0.02 mol L-1, and [AsPh3] = 0-0.07 mol L-1, at 322.6 K in THF. The only organopalladium(II) intermediate detected under catalytic conditions is 3a. The apparent activation parameters found for the coupling of 1 with 2a support an associative transmetalation step (ΔH((±))(obs) = 50 ± 2 kJ mol-1, ΔS((±))(obs) = -155 ± 7 J K-1 mol-1 in THF; and ΔH((±))(obs) = 70.0 ± 1.7 kJ mol-1, ΔS((±))(obs) = -104 ± 6 J K-1 mol-1 in chlorobenzene, with [1]0 = [2]0 = 0.2 mol L-1, [3a] = 0.01 mol L-1). The reactions of 2a with isolated trans-[PdR1X(AsPh3)2 (X = halide) show rates Cl > Br > I. From these observations, the following mechanism is proposed: Oxidative addition of R1X to PdL(n) gives cis- [PdR1XL2], which isomerizes rapidly to trans[PdR1XL2]. This trans complex reacts with the organotin compound following a S(E)2 (cyclic) mechanism, with release of AsPh3 (which explains the retarding effect of the addition of L), to give a bridge intermediate [PdR1L(μ-X)(μ-R2)SnBu3]. In other words, an L-for-R2 substitution on the palladium leads R2 and R1 to mutually cis positions. From there the elimination of XXnBu3 yields a three- coordinate species cis-[PdR1R2L], which readily gives the coupling product R1-R2.
- Casado, Arturo L.,Espinet, Pablo
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p. 8978 - 8985
(2007/10/03)
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- Preparation of oligosilanes containing perhalogenated silyl groups (-SiX3, -SiX2-, >SiX-, X = Cl, Br) and their hydrogenation by stannanes
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Starting from methylphenylsubstituted oligosilanes the disilanes SiX3-SiXi,Me3-i (i = 0, 1, 2; X = Cl, Br), trisilanes SiX2(SiXiMe3-i) (i = 0, 1) and branched tetrasilanes SiX(SiXMe2)3 were synthesized and their behavior towards the Lewis-base catalyzed hydrogenation by stannanes was investigated. In the case of methylchlorodisilanes SiCl3-SiCliMe3-i Si-Si bond cleavage competes with the hydrogenation reaction.
- Herzog,Roewer
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p. 217 - 223
(2007/10/03)
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- Isothiazoles. Part VII. An efficient palladinm-catalyzed functionalization of 3-amino-4-aryl-isothiazole 1,1-dioxides with organostannanes
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The palladium-catalyzed reaction of 5-bromo-3-diethylamino-4-(4-methoxyphenyl)-isothiazole 1,1-dioxide (3) with a variety of vinyl-, aryl-, heteroaryl- and alkynylstannanes 4 provides a general and efficient method for the synthesis of 5-substituted isothiazole 1,1-dioxides 5. Different reaction conditions (catalyst, solvent, temperature) were tested for the coupling. The best results were obtained using toluene at reflux and benzylchlorobis(triphenylphosphine)palladium as catalyst. When organostannanes appeared to be less reactive, prolonged heating resulted in the formation of variable amounts of the reduction product-3-diethyiamino-4-(4-methoxyphenyl)-isothiazole 1,1-dioxide (1).
- Clerici, Francesca,Erba, Emanuela,Gelmi, Maria Luisa,Valle, Marinella
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p. 15859 - 15866
(2007/10/03)
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- 1-Allylgermatrane. Synthesis, Structure and Reaction with Diazomethane
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Reaction of allyltribromogermarie (2), readily available from dibromo(1,4-dioxane)germanium(II) (1) and allylbromide, with tris(2-tributylstannoxyethyl)-amine (4) gives 1-allylgermatrane (3) in almost quantitative yield. 3 crystallizes from n-pentane as a colourless crystalline solid which was characterized by 1H and 13C NMR spectroscopy and by an X-ray crystal structure study. The atrane skeleton shows a strong conformational disorder; the GeN distance of 2.208(3) A suggests the presence of a coordinative Ge-N bond. Treatment of 1-allylgermatrane (3) with CH2N2 in the presence of catalytic amounts of Pd(OAc)2 affords 1-cyclopropylmethylgermatrane (5) in high yield.
- Zaitseva, Galina S.,Karlov, Sergey S.,Alekseyeva, Elena S.,Aslanov, Leonid A.,Avtomonov, Evgeni V.,Lorberth, Joerg
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- New Observations Concerning the Reactivity of Triorganotin Fluorides
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Me3SnF (1) reacts with many hydrolyzable chlorides to give Me3SnCl and the corresponding fluoride.The formation of PhPF2, (ClCH2)MeSiF2, F2PCH2PF2 and PF5 is described.The reaction of triorganotin fluorides (Ph3SnF, Bu3SnF) with CaBr2 yields pure triorganotin bromides. 1 was found to act either as a fluoride-acceptor or, towards PF5, as a fluoride-donor. - Keywords: Trimethylfluorostannane; Triorganohalo-Stannanes; Phosphorus-Fluorine Compounds; NMR Spectra
- Lambertsen, Thomas,Schmutzler, Reinhard
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p. 1583 - 1586
(2007/10/03)
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- C-, N- and C,N-Organostannyl Tetrazoles: Synthesis, Characterisation and Reactivity
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Open-chain C,N-organostannyl tetrazoles, R2R'Sn(CH2)nCN4SnBu3 (n = 2 or 3, R2R' = Ph3; n = 2, R2R' = Bu2Ph), have been synthesized by a cycloaddition reaction between R3Sn(CH2)nCN and SnBu3(N3).Prolonged heating of the reaction mixture yields the novel bicyclic species C,N-R2Sn(CH2)nCN4 (n = 2 or 3, R = Ph; n = 2, R = Bu).The reaction chemistry of both classes of compound has been studied, along with a reinvestigation of the parent 5-organo(N-triorganostannyl)tetrazoles RCN4SnR'3, by 13C and 119Sn NMR spectroscopy.The crystal structure of 2,2-diphenyl-1,7,8,9-tetraaza-2-stannabicyclonona-6,8-diene has also been determined.
- Blunden, Stephen J.,Mahon, Mary F.,Molloy, Kieran C.,Waterfield, Philip C.
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p. 2135 - 2144
(2007/10/02)
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- Haloalkylation process
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A process for the haloalkylation of certain tin, phosphorus and germanium halides is disclosed. The process is carried out typically in a halocarbon solvent at temperatures of less than 0° C. using as the haloalkylating reagent an admixture of a haloalkyl halide and tris(lower alkylamino)phosphine.
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- Simple procedure for conversion of a trialkyltin fluoride into the corresponding chloride or bromide
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Trialkyltin fluorides are converted into the chlorides or bromides on treatment with an excess of the corresponding sodium halide in tetrahydrofuran.
- Mitchell, Terence N.,Kwetkat, Klaus,Godry, Bernd
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p. 1633 - 1634
(2008/10/08)
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- PALLADIUM-CATALYZED REACTION OF ORGANIC HALIDES WITH ORGANOTIN COMPOUNDS INVOLVING OLEFIN INSERTION: SYNTHESIS OF 2,3-DISUBSTITUED NORBORNANES
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2,3-Disubstituted norbornanes were prepared by the palladium-catalyzed reaction of a ternary system composed of organic halide, organotin compound, and norbornene.The scope and limitations of this reaction are described.
- Kosugi, Masanori,Tamura, Hiroyuki,Sano, Hiroshi,Migita, Toshihiko
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p. 961 - 968
(2007/10/02)
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- Bromodestannylation reactions of some functionally substituted organotin compounds
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Bromodestannylation reactions are reported for several functional substituted organotin compounds in carbon tetrachloride and acetonitrile as solvents.The reactions in carbon tetrachloride proceed with a high degree of retention of configuration at the carbon involved in the electrophilic substitution, while in a polar solvent there is an increase in the amount of inversion product formed.The electrophilic cleavage in the β-trialkylstannyl esters takes place with a complete reversal of the normal sequence of Sn-C bond cleavage by halogens; this is explained by tin assistance.The configuration of some 3-trialkylstannylpropanenitriles, β-bromonitriles and β-bromoesters are assigned.Full, 1H, 13C and 119Sn NMR data are given.
- Chopa, A. B.,Koll, L. C.,Podesta, J. C.,Mitchell, T. N.
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p. 283 - 296
(2007/10/02)
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- Organotin biocides. XIV. Synthesis of new organotin heterocycles from thermal cyclisation of organotin tetrazoles. Crystal structure of 2,3,4,5-tetraaza-6-diphenylstannylbicyclonona-1,3-diene
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2-(Tributylstannyl)-5-(3'-triphenylstannylpropyl)tetrazole undergoes a thermal cyclisation to yield 2,3,4,5-tetraaza-6-diphenylstannnylbicyclonona-1,3-diene, the first of a new class of bicyclic organotin heterocycles.
- Mahon, Mary F.,Molloy, Kieran C.,Waterfield, Philip C.
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- Substituent effects upon the kinetics of hydrogen transfer from triorganotin hydrides to the 5-hexen-1-yl radical
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Steric and electronic substituent effects were probed for the hydrogen atom transfer reaction of a series of triorganotin hydrides with the 5-hexen-1-yl radical. Rate data were obtained for tributyltin hydride (1), triisopropyltin hydride (2), tri-tert-butyltin hydride (3), trineopentyltin hydride (4), trimesityltin hydride (5), and dibutylethoxytin hydride (6). Arrhenius parameters are reported for the reactions of 1-4 and 6; the reaction of 5 was studied only at 50°C. For compounds 1-4, the activation energy, Ea, decreased monotonically with increasing alkyl size from 3.9 ± 0.1 to 3.1 ± 0.1 kcal mol-1. The preexponential factor, expressed as log A, decreased monotonically from 9.4 ± 0.1 to 8.8 ± 0.1. The effect of the ethoxy substituent, 6, relative to an n-butyl substituent, 1, upon the activation energy was negligible (4.2 ± 0.2 versus 3.9 ± 0.1 kcal mol-1, respectively), but the preexponential factor, log A, increased from 9.4 ± 0.1 to 10.0 ± 0.1. The activation data for 1-4 are interpreted in terms of the steric requirements of the alkyl groups appended to tin. The lack of a significant substituent effect upon Ea by the ethoxy group is reflective of a nonpolarized transition state for the hydrogen atom transfer reaction.
- Pike, Philip W.,Gilliatt, Vernon,Ridenour, Michael,Hershberger, James W.
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p. 2220 - 2223
(2008/10/08)
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- A highly selective synthesis of R2SnX2 (R = alkyl, X = Br, Cl) species directly from tin and alkyl halides
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The reaction : Sn + 2RX -> SnR2X2 (X = Cl, Br) occurs at relatively low temperature (80 - 120 degC) and with selectives as high as 95 - 99percent in the presence of catalytic system fored by a crown ether and potassium iodide.The reaction is favoured by aprotic dipolar solvents such as dimethylformamide; the presence of an alkyl iodide as cocatalyst has a positive effect, the selectivity remaining unchanged.
- Ugo, R.,Chiesa, A.,Fusi, A.
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- Palladium Catalyzed Coupling Reaction of α-Bromo Ketones with Hexabutylditin
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Palladium-catalyzed reaction of α-bromo ketones with hexabutylditin in the presence of trimethylsilyl chloride gave enol trimethylsilyl ether in moderate to good yields.
- Kosugi, Masanori,Koshiba, Mamoru,Sano, Hiroshi,Migita, Toshihiko
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p. 1075 - 1076
(2007/10/02)
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- Production of organotin halides
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A process is disclosed for the direct production of organotin halides, particularly triorganotin halides by the reaction of elemental tin and an organotin halide in the presence of a reagent amount of an `onium compound of the general formula Cat+ X-. Cat+ X- may represent a quaternary ammonium or phosphonium group or a ternary sulphonium group, or may also represent a complex of an alkali metal or alkaline earth metal with a polyoxygen compound. High yields of triorganotin halide product are obtained in contrast to results of reactions wherein Cat+ X- is present in only catalytic amounts.
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- PALLADIUM CATALYZED REACTION OF ARYL BROMIDES WITH CYANOMETHYLTRIBUTYLTIN. AROMATIC CYANOMETHYLATION
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Palladium catalyzed reaction of aryl bromides with cyanomethyltributyltin gave arylacetonitriles in moderate yields.Aryl bromides having strong electron-withdrawing groups (such as acyl, cyano, nitro, etc.) cannot be applied to the reaction.
- Kosugi, Masanori,Ishiguro, Masahiro,Negishi, Yoshikazu,Sano, Hiroshi,Migita, Toshihiko
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p. 1511 - 1512
(2007/10/02)
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- Preparation of Some Silyl Esters and Study of Their Vibration Spectra in Gas and Condensed Phases
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A new preparative route for silyl esters is described, involving reaction of silyl bromide and trisalkyltin esters.The far infrared spectrum of some simple esters are reported; an investigation of the shifts in the carbonyl stretching band on condensation shows no significant differences in behaviour between methyl and silyl esters. - Keywords: Silyl esters, preparation; Vibration spectra
- Bett, William,Cradock, Stephen
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p. 193 - 198
(2007/10/02)
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- Electron Donor-Acceptor Complexes. 1. Linear Free Energy Correletion of the Charge-Transfer Transition Energy with the Kinetics of Halogenolysis of Alkylmetals
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Mulliken charge-transfer theory is used to relate the properties of transient donor-acceptor complexes between alkylmetals and halogens with the kinetics of the accompanying cleavage reaction (halogenolysis).The formulation derives from the charge-transfer transition energy hνCT which is proportional to the second-order rate constant for halogenolysis of a variety of tetraalkyltin compounds in hexane or carbon tetrachloride solutions.The description of the activation process for halogenolysis as an electron transfer in the CT complex, e.g., --> , leads to a linear free energy relationship in which the activation free energy is equal to the driving force for ion pair formation.The latter is equated to the charge-transfer transition energy plus a contribution from the solvation energy, by employing a comparative procedure for the evaluation of alkylmetals.An independent measure of the solvation energy obtained from the gas-phase ionization potentials of alkylmetals and their free energy changes in solution supports the electron-transfer formulation of the activation process.The charge-transfer mechanism is generalized for the halogenolysis of alkylmetals.
- Fukuzumi, S.,Kochl, J.K.
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p. 2246 - 2254
(2007/10/02)
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- Electron-Transfer Activation in Electrophilic Mechanisms. Cleavage of Alkylmetals by Mercury(II) Complexes
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The disappearance of the transient charge-transfer (CT) absorption bands coincides with the electrophilic (SE2) cleavage of homologous series of alkyltin compounds by various mercury(II) halides, cyanide, and carboxylates.The second-order kinetics for HgCl2 cleavage afford rate constants which vary in a rather unaccountable way with the structure of the alkyltin compound and with the polarity of the solvent.Furthermore, the relative reactivities of these alkyltin compounds in the analogous electrophilic cleavage by I2 or Br2 show poor correlations with HgCl2 cleavages, in different solvents.However, the description of the activation process as an electron transfer in the precursor complex, e.g., -> +HgCl2->, stems from the CT transition energy and leads to a linear free energy relationship in which the activation free energy is equal to the driving force for the formation of the ion pair.The latter is readily dissected by eq 18 into separate changes in electronic, steric and solvation energies.With this mechanistic formulation, the reactivities of various alkyltin compounds follow a remarkably simple linear correlation with the ionization potentials and the solvent effects, in the comparison with I2 and Br2 cleavages.Moreover, the reactivities of the various mercury(II) derivatives relate directly to differences in their electron affinities.
- Fukuzumi, S.,Kochi, J. K.
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p. 7290 - 7297
(2007/10/02)
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- METAL-HALOGEN BONDING STUDIES WITH GROUP IV A TRIALKYLMETAL HALIDES
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Halogen redistribution reactions have been found to take place between benzyl bromide or benzyl iodide and the Group IV A silicon, germanium, tin, and lead containing trialkylmetal chlorides.However, for the reactions of the Si, Ge and Sn compounds, a quaternary ammonium halide catalyst was necessary to enable the equilibria to be established at reasonably rapid rates.The equilibrium constants at 50 deg C have been measured for each of these halogen redistributions.They have been found to increase gradually on going down in Group IV A from silicon to lead, being conside rably less than unity in the case of silicon and somewhat greater than unity in the case of lead for both the R3MCl + BzBr and R3MCl + BzI reactions.The ΔG0 values for these equilibria have been calculated, and it is suggested that their differences may be explained in terms of the relative importance of p?-d? contributions to the halogen-metal bonding in the various Group IV A trialkylmetal halide systems.
- Friedrich, Edwin C.,Abma, Charles B.,Vartanian, Paul F.
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p. 203 - 212
(2007/10/02)
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2-Halogenoalkoxytributyltin compounds have been prepared from tributylethoxytin and 1,2-halohydrins. The thermal degradation and its mechanism are investigated. These reactions offer a convenient way to prepare epoxides.
- Delmond, Bernard,Pommier, Jean-Claude,Valade, Jacques
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- Mechanisms of the rupture of the carbon-tin bond by halogens II. Free-radical substitution in solution
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The experiments describes in this paper show that the light-induced bromodemetallation of tetraalkyltins in chlorobenzene is a free radical substitution on tin, followed by a propagation step: {A figure is presented}. The stabilisation of R? by hyperconjugation seems to be an important factor for the reaction, but there is evidence for the influence of the other three substituents of tin and of the nature of the attacking radical on the reaction mechanism. The relation between the strucutre and the reactivity of tetraalkyltins suggests that the carbon-tin bond is only slightly loosened in the transition state; this agrees with the great reactivity of the Br atom.
- Boue, S,Gielen, M,Nasielski, J
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p. 461 - 479
(2008/10/08)
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- Mechanisms of the rupture of the carbon-tin bond by halogens I. Electrophilic substitution at a saturated carbon atom
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In chlorobenzene, some tetraalkyltins are able to alter the reactivity of bromine towards their homologues and this is no more true in solvents of high nucleophilicity. This perturbating power, which is linked to the nature of the substituents bound to the metal, is best explained by the formation of a complex R4Sn(-)-X(+)2 which acts as a modified halogen towards another alkyltin molecule. This mixing-effect changes sometimes considerably the kinetics and the mechanism of the reactions and suggests that the accessibility of empty 5d orbitals of the metal plays an important part in the reactivity of tetraalkyltins, as well in SE2 as in radical substitutions.
- Boue, S,Gielen, M,Nasielski, J
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p. 481 - 494
(2008/10/08)
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