- Reactions of organosilicon-group V compounds with nitrosyl chloride
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The reactions of (CH3)3SiN(CH3)2, (CH3)3SiP(CH3)2, and (CH3)3SiAs(CH3)2 with NOCl have been studied. The products observed are, respectively: (CH3)3SiCl and (CH3)2NNO; (CH3)3SiOSi(CH3)3, N2O, NO, N2, (CH3)3SiCl, (CH3)2P(O)Cl, and a glassy solid; (CH3)3SiOSi(CH3)3, N2O, and (CH3)2AsCl.
- Byrne, Joseph E.,Russ, Charles R.
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- Siloxane derivatives of 2-mercaptobenzothiazole
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First organosilicon captax derivatives were obtained from 2-mercaptobenzothiazole and 1-(iodomethyl)-1,1,3,3,3-pentamethyl-or 1,3-bis(iodomethyl)-1,1,3,3-tetramethyldisiloxanes in the absence or in the presence of bases.
- Zhilitskaya, Larisa V.,Yarosh, Nina O.,Shagun, Lyudmila G.,Dorofeev, Ivan A.,Larina, Lyudmila I.
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- Reactivity of Cyclic Silenolates Revisited
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The stable exocyclic silenolates 2a-c (2a, R = Mes; 2b, R = o-Tol; 2c, R = 1-Ad) were fully characterized by NMR and UV-vis spectroscopy. According to spectroscopic and structural features, 2a-c are best described as acyl silyl anions (tautomeric structure I) in solution. This behavior is also reflected by the reaction of 2a,c with MeI. Both alkylation reactions take place at the corresponding silicon atom and lead to the formation of the methylated structures 4a,b in nearly quantitative yields. Furthermore, the thermal stability of exocyclic silenolates 2a,c was investigated. In the case of 2a, a thermally induced intramolecular sila-Peterson alkenation was observed at 60 °C. This transformation allowed straightforward access to 2-oxahexasilabicyclo[3.2.1]octan-8-ide 5 as a structurally complex, bicyclic silicon framework. In contrast to that, heating of 2c, as an example of an alkyl-substituted silenolate, led to an unexpected degradation to uncharacterized polymers. However, we were able to isolate the 1-adamantyl-substituted, bicyclic compound 8, which is structurally closely related to 5, by the treatment of 1,4-dipotassium-1,4-bis(trimethylsilyl)cyclohexasilane with 1 equiv of 1-adamantoyl chloride. Again an intramolecular sila-Peterson alkenation is responsible for the formation of 8. The mechanism for this highly selective reaction sequence is outlined and supported by density functional theory (DFT) calculations, which highlight the thermodynamic driving force and the low activation barriers of this multistep transformation.
- Haas, Michael,Leypold, Mario,Schuh, Lukas,Fischer, Roland,Torvisco, Ana,Stueger, Harald
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- Ether-like Si-Ge hydrides for applications in synthesis of nanostructured semiconductors and dielectrics
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Hydrolysis reactions of silyl-germyl triflates are used to produce ether-like Si-Ge hydride compounds including H3SiOSiH3 and the previously unknown O(SiH2GeH3)2. The structural, energetic and vibrati
- Tice, Jesse B.,Weng, Change,Tolle, John,D'Costa, Vijay R.,Singh, Rachna,Menendez, Jose,Kouvetakis, John,Chizmeshya, Andrew V. G.
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- Mechanistic insights on azide-nitrile cycloadditions: On the dialkyltin oxide-trimethylsilyl azide route and a new vilsmeier-haack-type organocatalyst
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The mechanism of the azide-nitrile cycloaddition mediated by the known dialkylltin oxide-trimethylsilyl azide catalyst system has been addressed through DFT calculations. The catalytic cycle for this tin/silicon complex-based mechanism has been thoroughly examined, disclosing the most plausible intermediates and the energetics involved in the rate enhancement. In addition, a new catalyst, 5-azido-1-methyl-3,4-dihydro-2H-pyrrolium azide, is presented for the formation of tetrazoles by cycloaddition of sodium azide with organic nitriles under neutral conditions. The efficiency of this organocatalyst, generated in situ from N-methyl-2-pyrrolidone (NMP), sodium azide, and trimethylsilyl chloride under reaction conditions, has been examined by preparation of a series of 5-substituted-1H-tetrazoles. The desired target structures were obtained in high yields within 15-25 min employing controlled microwave heating. An in depth computational analysis of the proposed catalytic cycle has also been addressed to understand the nature of the rate acceleration. The computed energy barriers have been compared to the dialkylltin oxide-trimethylsilyl azide metal-based catalyst system. Both the tin/silicon species and the new organocatalyst accelerate the azide-nitrile coupling by activating the nitrile substrate. As compared to the dialkylltin oxide-trimethylsilyl azide method, the organocatalytic system presented herein has the advantage of higher reactivity, in situ generation from inexpensive materials, and low toxicity.
- Cantillo, David,Gutmann, Bernhard,Kappe, C. Oliver
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- Bonding studies on zinc, cadmium, and mercury alkyls and amides, Zn(CH2EMe3)2 (E = C or Si) and M2 (M = Zn, Cd, or Hg). Heats of hydrolysis, standard heats of formation, and Zn-C and M-N (M = Zn, Cd, or Hg) bond energy terms
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Calorimetric measurements have been carried out on the heats of hydrolysis of the homoleptic zinc alkyls Zn(CH2EMe3)2 (E = C or Si) and bis(trimethylsilyl)amides M2 (M = Zn, Cd, or Hg) at 25 +/- 0.01 deg C in aqueous hydrochloric (1 M; for the
- Guemruekcueoglue, Ismail E.,Jeffery, John,Lappert, Michael F.,Pedley, J. Brian,Rai, Audesh K.
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- 1,2-Migration of the trimethylsilyl group in free radicals
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EPR spectroscopic observations and product studies showed that the trimethylsilyl group undergos 1,2-migration from carbon to nitrogen in aminyl radicals, Me3SiCH2NH -> CH2NHSiMe3, and from carbon to oxygen in alkoxyl radicals, Me3SiCH2O -> CH2OSiMe3.
- Harris, Joanna M.,MacInnes, Iain,Walton, John C.,Maillard, Bernard
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- Generation and Reactivity of a NiIII2(μ-1,2-peroxo) Complex
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High-valent transition metal-oxo, -peroxo, and -superoxo complexes are crucial intermediates in both biological and synthetic oxidation of organic substrates, water oxidation, and oxygen reduction. While high-valent oxygenated complexes of Mn, Fe, Co, and Cu are increasingly well-known, high-valent oxygenated Ni complexes are comparatively rarer. Herein we report the isolation of such an unusual high-valent species in a thermally unstable NiIII2(μ-1,2-peroxo) complex, which has been characterized using single-crystal X-ray diffraction and X-ray absorption, NMR, and UV-vis spectroscopies. Reactivity studies show that this complex is stable toward dissociation of oxygen but reacts with simple nucleophiles and electrophiles.
- Zhao, Norman,Filatov, Alexander S.,Xie, Jiaze,Hill, Ethan A.,Rogachev, Andrey Yu.,Anderson, John S.
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- Laser-powered homogeneous pyrolysis of 1,1-dimethyl-1-silacyclobutane in the presence of some common monomers
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Laser-induced homogeneous pyrolysis of 1,1-dimethyl-1-silacyclobutane yields 1,1,3,3-tetramethyl-1,3-disilacyclobutane and ethene as major products.In the presence of vinyl acetate, allyl methyl ether, acrolein, methyl vinyl ether, methyl acrylate or meth
- Pola, Josef,Cukanova, Dana,Minarik, Milan,Lycka, Antonin,Tlaskal, Jaroslav
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- Catalytic Metal-Free Deoxygenation of Nitrous Oxide with Disilanes
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Because of its high kinetic stability, conditions to reduce the greenhouse gas N2O are limited; therefore, a better understanding of N2O chemistry and N-O bond cleavage is required. In this work, N2O was deoxygenated under metal-free conditions. Using disilanes as reducing agents and a catalytic amount of fluoride anions or alkoxides allowed a mild reduction at ambient pressure and temperature. DFT calculations unveiled the mechanism, which shows a nucleophilic addition of a silyl anion to the central N atom of N2O and release of N2 from a pseudo-Brook rearrangement.
- Anthore-Dalion, Lucile,Nicolas, Emmanuel,Cantat, Thibault
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- GENERATION AND REARRANGEMENT OF A 1-NORBORNENE IN PYROLYSIS OF 1-SILA-OXYNORBORNANES
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Gas phase pyrolysis of 1-sila-2-oxynorbornenes yields a nortricyclene which is proposed to arise from a β-elimination to form a 1-norbornene, which isomerizes to a 2-norbornacylidene which undergoes γ-CH insertion.
- Barton, Thomas J.,Yeh Ming-Hsiung
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- Trimethylethoxysilane Liquid-Phase Hydrolysis Equilibrium and Dimerization Kinetics: Catalyst, Nonideal Mixing, and the Condensation Route
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Although the kinetics of organoethoxysilane hydrolytic (poly)condensation have been studied under kinetically simplified conditions, materials are actually synthesized from nonideal mixtures with high monomer and catalyst concentrations. Using 29Si nuclear magnetic resonance, we study the hydrolysis of trimethylethoxysilane and the dimerization of the resulting silanol in aqueous ethanol at monomer and catalyst concentrations typical of organically modified silicate synthesis. Under acidic conditions, we find that when (and only when) the effects of solvent composition on catalyst activity are considered, it becomes clear that water-producing condensation is the dominant dimerization route. Under basic conditions, the extent of deprotonation of the weakly acidic silanol passes through a minimum during reaction, thereby producing an anomolous trend in reaction rate. This necessitates a kinetic model which is first order in both silanol and deprotonated silanol and which accounts for changing deprotonation.
- Rankin, Stephen E.,Sefcik, Jan,McCormick, Alon V.
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- Stationary and Pulsed Photolysis and Pyrolysis of 1,1-Dimethylsilacyclobutane
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A study of the photolysis of 1,1-dimethylsilacyclobutane at 147 - 214 nm shows that of the four primary processes identified the predominant mode of decomposition is to C2H4 and dimethylsilaethene.Evidence from experiments in the presence of SF6 suggests that the dimethylsilaethene is formed initially in a vibrationally excited state: +hν -> Me2SiCH2v + CH2=CH2.Laser pulsed photolysis experiments at 193 nm have been carried out to measure tha absorption spectrum of Me2SiCH2, its absorption cross section, and the rate constant for Me2SCH2 combination: 2Me2SiCH2 -> (Me2SiCH2)2.The values obtained are ? (240 nm, base e) = (1.0 +/- 0.2)E-17 cm2 and k7 = (3.3 +/- 0.8)E-11 cm3 s-1.The kinetics of the pyrolysis of have also been reexamined, yielding the following rate constant expressions: k1/(s-1) = E(15.46 +/- 0.13) exp(-(31043 +/- 218)/T) and k-1/k71/2/(cm3/2s-1/2) = E(-7.0 +/- 0.3) exp(-(7850 +/- 300)/T).From these results, the heat of formation, ?-bond energy, and entropy of Me2SiCH2, have been deduced: ΔHfθ (g, 298 K) = 36 +/- 7 kJ mol-1, B? = 157 +/- 11 kJ mol-1, and Sθ(g, 298 K) = 332 +/- 8 J mol-1 K-1.
- Brix, Th.,Arthur, N. L.,Potzinger, P.
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- FT-IR study of the gas phase thermolysis of trimethylsilyl acetate
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Thermolysis of neat trimethylsilyl acetate has been investigated in the temperature range 723-818 K under static conditions using Fourier transform infrared spectroscopy. The principal gaseous products formed during the thermal decomposition are methane, hexamethyldisiloxane, cyclohexamethyltrisiloxane, carbon dioxide, and carbon monoxide, the relative amounts of which vary with the temperature. Small amounts of water and ethanoic acid are also formed. Loss of trimethylsilyl acetate is first-order over the whole temperature range; the first-order rate constants vary from 1.66 × 10-5s-1 at 723 K to 15.7 × 10-5s-1 at 818 K, leading to an activation energy Ea of 104(5)kJ mol-1. In the presence of methyl iodide the decomposition is substantially faster and the products are methane, hexamethyldisiloxane and ethanoic acid. Decomposition is also faster in the presence of nitric oxide and oxygen, although complete identification of the product mixtures was not possible in these cases. The mechanisms of the reactions are interpreted in terms of principally radical reactions involving initial homolytic dissociation of the Me3SiO-C(O)CH3 bond.
- Harrison, Philip G.,Torr, Ashley
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- Catalytic Iodination of the Aliphatic C-F Bond by YbI3(THF)3: Mechanistic Insight and Synthetic Utility
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A facile iodination protocol of unactivated alkyl fluorides using catalytic amounts of YbI3(THF)3 in the presence of iodotrimethylsilane as a stoichiometric fluoride trapping agent is presented. 1H NMR spectroscopy demonstrates a two-step catalytic cycle where TMSI regenerates active YbI3(THF)3. Finally, the catalytic reaction is extended into a one-pot procedure to demonstrate a potential application of the method. Overall, the findings present a distinct strategy for C-F bond transformations in the presence of catalytic YbI3(THF)3.
- Janjetovic, Mario,Ekebergh, Andreas,Tr?ff, Annika M.,Hilmersson, G?ran
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- Synthesis and characterization of three homoleptic bismuth silanolates: [Bi(OSiR3)3] (R = Me, Et, iPr)
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The bismuth tris(triorganosilanolates) [Bi(OSiR3)3] (1, R = Me; 2, R = Et; 3, R = iPr) were prepared by reaction of R 3SiOH with [Bi(OtBu)3]. Compound 1 crystallizes in the triclinic space group P1 with Z = 2 and the lattice constants a = 10.323(1) A, b = 13.805(1) A, c = 21.096(1) A and α = 91.871(4)°, β = 94.639(3)°, γ = 110.802(3)°. In the solid state compound 1 is a trimer as result of weak intermolecular bismuth-oxygen interactions with Bi-O distances in the range 2.686(6)-3.227(3) A. The coordination at the bismuth atoms Bi(1) and Bi(3) is best described as 3+2 coordination whereas Bi(2) shows a 3+3 coordination. The intramolecular Bi-O distances fall in the range 2.041(3)-2.119(3) A. Compound 3 crystallizes in the orthorhombic space group Pbcm with Z = 4 and the lattice constants a = 7.201(1) A, b = 23.367(5) A and c = 20.893(1) A, whereas the triethylsilyl-derivative 2 is liquid. In contrast to [Bi(OSiMe3) 3] (1) compound 3 is monomeric in the solid state, but shows similar intramolecular Bi-O distances in the range 1.998(2)-2.065(5) A. The bismuth silanolates are highly soluble in common organic solvents and strongly moisture sensitive. Compound 1 shows the lowest thermal stability.
- Paalasmaa, Sanna,Mansfeld, Dirk,Schuermann, Markus,Mehring, Michael
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- A janus-headed lewis superacid: Simple access to, and first application of Me3Si-F-Al(ORF)3
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Upon reaction of gaseous Me3SiF with the in situ prepared Lewis acid Al(ORF)3, the stable ion-like silylium compound Me3Si-F-Al(ORF)3 1 forms. The Janusheaded 1 is a readily available smart Lewis acid that differentiates between hard and soft nucleophiles, but also polymerizes isobutene effectively. Thus, in reactions of 1 with soft nucleophiles (Nu), such as phosphanes, the silylium side interacts in an orbital-controlled manner, with formation of [Me3Si-Nu]+ and the weakly coordinating [F-Al(ORF)3]-or [(FRO)3Al-F-Al(ORF)3]- anions. If exchanged for hard nucleophiles, such as primary alcohols, the aluminum side reacts in a charge-controlled manner, with release of FSiMe3 gas and formation of the adduct R(H)O-Al(ORF)3. Compound 1 very effectively initiates polymerization of 8 to 21 mL of liquid C4H8 in 50 mL of CH2Cl2 already at temperatures between -57 and -30 8C with initiator loads as low as 10 mg in a few seconds with 100 % yield but broad polydispersities.
- Rohde, Michael,Muller, Lutz O.,Himmel, Daniel,Scherer, Harald,Krossing, Ingo
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- The pentamethylcyclopentadienylsilicon(II) cation as a catalyst for the specific degradation of oligo(ethyleneglycol) diethers
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Catalytic open sandwiches: Oligo(ethyleneglycol) diethers RO(CH 2CH2O)nR are degraded by the unusual catalyst Cp Si+ (see scheme). The open coordination sphere at silicon allows up to four Si-O contacts; crystal structure data of the reactive compounds [Cp Si(dme)]+BR4- and [Cp Si([12]crown-4)] +BR4- (R=C6F5) show weakly bound ether molecules. Copyright
- Leszczynska, Kinga,Mix, Andreas,Berger, Raphael J. F.,Rummel, Britta,Neumann, Beate,Stammler, Hans-Georg,Jutzi, Peter
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- DIRECT PHOTOLYSIS OF TETRAMETHYLSILANE IN THE GAS AND LIQUID PHASES.
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The photolysis of tetramethylsilane at the long wavelength side of the absorption spectrum gives rise to two main primary photochemical processes: a simple Si-C bond-breaking process with a quantum yield of 0. 55 plus or minus 0. 17 and a methane elimination reaction with a quantum yield of 0. 22 plus or minus 0. 07. The radicals disappear by recombination and addition reactions to dimethylsilaethylene. Only an upper limit for the ratio of disproportionation to recombination of 0. 13 for the trimethylsilyl radicals can be given. Beside the radical addition reaction dimethylsilaethylene also dimerizes. A semiquantitative evaluation of the data shows that the radical addition reaction as well as the dimerization reaction proceed with a negligible activation energy.
- Bastian,Potzinger,Ritter,Schuchmann,von Sonntag,Weddle
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- Reactions of trimethyliodosilane with mono-, di-, and trioxacycloalkanes
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The reactions of Me3SiI with mono-, di-, and trioxacycloalkanes have been studied first.Preparative methods for the synthesis of some promising synthones, namely α,ω-diiodoalkanes, α,ω-alkanediols, and iodomethyl ω-iodoalkyl ethers, have been developed based on these reactions.The effect of the cycle size and the nature of the substituent on the course of the reactions is demonstrated.Schemes for the mechanism of the reactions are suggested.
- Voronkov, M. G.,Dubinskaya, E. I.
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- Catalytic Disproportionation of Formic Acid to Methanol by using Recyclable Silylformates
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A novel strategy to prepare methanol from formic acid without an external reductant is presented. The overall process described herein consists of the disproportionation of silyl formates to methoxysilanes, catalyzed by ruthenium complexes, and the production of methanol by simple hydrolysis. Aqueous solutions of MeOH (>1 mL, >70 percent yield) were prepared in this manner. The sustainability of the reaction has been established by recycling of the silicon-containing by-products with inexpensive, readily available, and environmentally benign reagents.
- Cantat, Thibault,Chauvier, Clément,Imberdis, Arnaud,Thuéry, Pierre
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- Reaction of Trimethylsilyl Benzhydryl Ethers with Methyl N-(Trimethylsilyl)pyroglutamate: An Easy and Rapid N-Alkylation
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In the presence of a small amount of catalyst (mainly triflic acid), methyl N-(trimethylsilyl)pyroglutamate quickly reacts with benzhydryl chlorides or preferentially with trimethylsilyl benzhydryl ethers to give methyl N-(benzhydryl)pyroglutamates in nearly quantitative isolated yields.
- Rigo, Beno?t,Gautret, Philippe,Legrand, Anne,Hénichart, Jean-Pierre,Couturier, Daniel
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- Preparation of Thionylimide Complexes of Titanium, Zirconium, and Hafnium. Crystal Structure of
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The compounds , (Zr(cp)(η-C5Me5)2(NSO)2>, , and (Hf(cp)(η-C5Me5)(NSO)2> (cp = η-C5H5) have been prepared from corresponding metal halides and K(NSO).The transition-metal-bonded NSO groups can be transformed into NSNSiMe3 by reaction with Li, giving .A compound containing three NSO ligands has been prepared from the reaction of SnMe3(NSO) and .The X-ray crystal structure of reveals a pseudo-tetrahedral co-ordination of the metal, with two nitrogen-bonded NSO ligands forming a nearly planar Zr(NSO)2 unit.
- Plenio, Herbert,Roesky, Herbert W.,Edelmannn, Frank T.,Noltemeyer, Mathias
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- Metathesis of silicon-containing olefins. X. Metathesis of vinyltrimethylsilane catalyzed by ruthenium complexes
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Self metathesis of vinyltrimethylsilane in the presence of an oxygenated benzene solution of RuCl2(PPh3)3 and RuH2(PPh3)4 follows an unusual course and yields two products, 1,2-bis(silyl)ethene (E) and 1,1-bis(silyl)ethene, with products of dimerization, namely 1,4-bis(silyl)butenes-2 (E + Z) and butenylsilanes as well as hexamethyldisiloxane.Gaseous ethylene and traces of ethane were also detected.It is proposed that vinylsilane is inserted into the Ru-Si bond (via ortho-metallation of the ruthenium triphenylphosphine complex) in competition with pathways involving metal-carbene species.Complexes of ruthenium containing no phenylphosphine give stereoselectively only the (E)-product of metathesis (even in the absence of oxygen and hydrosilane co-catalysts) accompanied by traces of the same by-products. Key words: Silicon; Ruthenium; Metathesis; Olefin
- Marciniec, Bogdan,Pietraszuk, Cezary,Foltynowicz, Zenon
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- Siloxane basicity toward strong acid in nonpolar solution
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The relative basicities of ten siloxanes and an ether were studied in benzene by determining from visible spectroscopic measurements the thermodynamic constants for the competition between the substrate and a reference base (4-chloro-2-nitroaniline) for acid (trifluoromethanesulfonic acid): RB-HA + S ? RB + S·HA. The Keq values were considered as a measure of basicity with the following order established and explained by inductive effects in the protonated species: permethyl linear siloxanes (Me3Si(OSiMe2)nOSiMe3, n = 0-3) > dibutyl ether > HMe2SiOSiMe2H > branched siloxanes ((Me3SiO)3SiMe, (Me3SiO)4Si) > cyclic siloxanes ((Me2SiO)n, n = 3-5). The ΔH and ΔS values were positive and increased with higher basicity; this behavior was attributed to differential solvation of ion pairs.
- Shepherd, Brian D.
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- THE SEARCH FOR THE ETHYNYL CATION: NITROSATION OF N,N-BIS(TRIMETHYLSILYL)YNAMINES
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The reaction of bis-silylated ynamines with different nitrosyl reagents affords products derived from an electrophilic attack at the β-carbon atom and not the expected alkynyldiazonium salts.
- Alvarez, Roberto Martinez,Hanack, Michael,Schmid, Thomas,Subramanian, L. R.
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- Highly Selective Synthesis of Hydrosiloxanes by Au-Catalyzed Dehydrogenative Cross-Coupling Reaction of Silanols with Hydrosilanes
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We report a highly selective synthesis of siloxane building blocks containing SiH2 or SiH functionalities. AuCl(PPh3)/PPh3 or AuCl(PPh3)/PnBu3 system catalyzed the reaction of trihydrosilanes with silanols giving SiH2-containing siloxanes exclusively. On the other hand, a highly selective reaction of dihydrosilanes with silanols to afford SiH-containing siloxanes was achieved by simply changing the phosphine ligand to a bidentate one, xantphos. Usefulness of SiH2-containing siloxanes was demonstrated by the synthesis of a trisiloxane, Et3SiOSi(Ph)(H)OSitBuMe2, and a pentasiloxane, Ph2Si(OSiHPhOSiEt3)2, bearing SiH functionalities.
- Satoh, Yasushi,Igarashi, Masayasu,Sato, Kazuhiko,Shimada, Shigeru
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- A One-Pot Synthesis of Trimethylsilyl Fluoride
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Trimethylsilyl fluoride (2) is prepared in a most simple way from trimethylsilyl chloride and solid potassium fluoride in the presence of a phase-transfer catalyst and a few drops of water.
- Dehmlow, E. V.,Fastabend, U.,Kessler, M.
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- CO2 conversion to isocyanate via multiple N-Si bond cleavage at a bulky uranium(III) complex
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The reaction of the sterically saturated uranium(iii) tetrasilylamido complex [K(18c6)][U(N(SiMe3)2)4] with CO2 leads to CO2 insertion into the U-N bond affording the stable U(iv) isocyanate complex [K(18c6)][U(N(SiMe3)2)3(NCO)2]n that was crystallographically characterized. DFT studies indicate that the reaction involves the [2+2] cyclo-addition of a double bond of OCO to the U-N(SiMe3)2 bond and proceeds to the final product through multiple silyl migration steps.
- Camp, Clément,Chatelain, Lucile,Kefalidis, Christos E.,Pécaut, Jacques,Maron, Laurent,Mazzanti, Marinella
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- Facile Synthesis of the Dicyanophosphide Anion via Electrochemical Activation of White Phosphorus: An Avenue to Organophosphorus Compounds
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Organophosphorus compounds (OPCs) have gained tremendous interest in the past decades due to their wide applications ranging from synthetic chemistry to materials and biological sciences. We describe herein a practical and versatile approach for the trans
- Liu, Liu Leo,Mei, Yanbo,Yan, Zeen
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supporting information
p. 1517 - 1522
(2022/02/01)
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- Alkali Metal Ions Dictate the Structure and Reactivity of an Iron(II) Imido Complex
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The presence of redox innocent metal ions has been proposed to modulate the reactivity of metal ligand multiple bonds; however, insight from structure/function relationships is limited. Here, alkali metal reduction of the Fe(III) imido complex [Ph2B(tBuIm
- Gao, Yafei,Pink, Maren,Smith, Jeremy M.
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supporting information
p. 1786 - 1794
(2022/02/10)
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- Organic Electrochemistry: Expanding the Scope of Paired Reactions
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Paired electrochemical reactions allow the optimization of both atom and energy economy of oxidation and reduction reactions. While many paired electrochemical reactions take advantage of perfectly matched reactions at the anode and cathode, this matching of substrates is not necessary. In constant current electrolysis, the potential at both electrodes adjusts to the substrates in solution. In principle, any oxidation reaction can be paired with any reduction reaction. Various oxidation reactions conducted on the anodic side of the electrolysis were paired with the generation and use of hydrogen gas at the cathode, showing the generality of the anodic process in a paired electrolysis and how the auxiliary reaction required for the oxidation could be used to generate a substrate for a non-electrolysis reaction. This is combined with variations on the cathodic side of the electrolysis to complete the picture and illustrate how oxidation and reduction reactions can be combined.
- Moeller, Kevin D.,Wu, Tiandi
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supporting information
p. 12883 - 12890
(2021/05/07)
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- Dimensional Reduction of Lewis Acidic Metal-Organic Frameworks for Multicomponent Reactions
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Owing to hindered diffusions, the application of porous catalytic materials has been limited to relatively simple organic transformations with small substrates. Herein we report a dimensional reduction strategy to construct a two-dimensional metal-organic framework (MOF), Zr6OTf-BTB, with 96% accessible Lewis acidic sites as probed by the bulky Lewis base pivalonitrile. With nearly free substrate accessibility, Zr6OTf-BTB outperformed two three-dimensional MOF counterparts of similar Lewis acidity (Zr6OTf-BPDC and Zr6OTf-BTC) in catalyzing sterically hindered multicomponent reactions (MCRs) for the construction of tetrahydroquinoline and aziridine carboxylate derivatives with high turnover numbers (TONs). Zr6OTf-BTB was also superior to the homogeneous benchmark Sc(OTf)3 with nearly 14 times higher TON and 9 times longer catalyst lifetime. Furthermore, the topology-activity relationships in these Zr-based Lewis acidic MOFs were rationalized by comparing their Lewis acidity, numbers of Lewis acidic sites, and sterically accessible Lewis acidic sites. Zr6OTf-BTB was successfully used to construct several bioactive molecules via MCRs with excellent efficiency. This dimensional reduction strategy should allow the development of other MOF catalysts for synthetically useful and complicated organic transformations.
- Feng, Xuanyu,Song, Yang,Lin, Wenbin
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supporting information
p. 8184 - 8192
(2021/06/27)
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- Sustainable Catalytic Synthesis of Diethyl Carbonate
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New sustainable approaches should be developed to overcome equilibrium limitation of dialkyl carbonate synthesis from CO2 and alcohols. Using tetraethyl orthosilicate (TEOS) and CO2 with Zr catalysts, we report the first example of sustainable catalytic synthesis of diethyl carbonate (DEC). The disiloxane byproduct can be reverted to TEOS. Under the same conditions, DEC can be synthesized using a wide range of alkoxysilane substrates by investigating the effects of the number of ethoxy substituent in alkoxysilane substrates, alkyl chain, and unsaturated moiety on the fundamental property of this reaction. Mechanistic insights obtained by kinetic studies, labeling experiments, and spectroscopic investigations reveal that DEC is generated via nucleophilic ethoxylation of a CO2-inserted Zr catalyst and catalyst regeneration by TEOS. The unprecedented transformation offers a new approach toward a cleaner route for DEC synthesis using recyclable alkoxysilane.
- Putro, Wahyu S.,Ikeda, Akira,Shigeyasu, Shinji,Hamura, Satoshi,Matsumoto, Seiji,Lee, Vladimir Ya.,Choi, Jun-Chul,Fukaya, Norihisa
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p. 842 - 846
(2020/12/07)
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- PROCESSES FOR SYNTHESIZING UNSYMMETRICAL DISILOXANES
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Described herein are methods for making alkenyl disiloxanes, comprising combining an alkenyl halosilane with an alkyl halosilane and adding the mixture to water, an acidic aqueous solution, or a basic aqueous solution. The ratio of the alkenyl halosilane to the alkyl halosilane is about 10:1 to about 1:10. The alkenyl halosilane and the alkyl halosilane are mixed at about 20 °C to about 45 °C. The reaction product is separated and washed with saturated alkali carbonate solution.
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Paragraph 0049-0051
(2021/06/22)
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- Direct growth of crystalline triazine-based graphdiyne using surface-assisted deprotection-polymerisation
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Graphdiyne polymers have interesting electronic properties due to their π-conjugated structure and modular composition. Most of the known synthetic pathways for graphdiyne polymers yield amorphous solids because the irreversible formation of carbon-carbon bonds proceeds under kinetic control and because of defects introduced by the inherent chemical lability of terminal alkyne bonds in the monomers. Here, we present a one-pot surface-assisted deprotection/polymerisation protocol for the synthesis of crystalline graphdiynes over a copper surface starting with stable trimethylsilylated alkyne monomers. In comparison to conventional polymerisation protocols, our method yields large-area crystalline thin graphdiyne films and, at the same time, minimises detrimental effects on the monomers like oxidation or cyclotrimerisation side reactions typically associated with terminal alkynes. A detailed study of the reaction mechanism reveals that the deprotection and polymerisation of the monomer is promoted by Cu(ii) oxide/hydroxide species on the as-received copper surface. These findings pave the way for the scalable synthesis of crystalline graphdiyne-based materials as cohesive thin films.
- Amsalem, Patrick,Bojdys, Michael J.,Burmeister, David,Huang, Jieyang,Kass, Dustin,Koch, Norbert,Kulkarni, Ranjit,Müller, Johannes,Martin, Andréa,Trunk, Matthias
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p. 12661 - 12666
(2021/10/19)
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- Reactions of 1-Germatranol Hydrate with Dicarboxylic Acids
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Abstract: The reactions of 1-germatranol hydrate with malonic, succinic, maleic, cork, sebacic acids, and bistrimethylsilyl ester of succinic acid, and also of bis(germatran-1-yl)oxane with succinic acid in acetonitrile, water, methanol, and dimethylsulfoxide were studied. In organic solvents, mono- and dicarboxyl-substituted 1-germatranols are formed, which, like 1-germatranol, are reversibly hydrolyzed with water in an acidic medium. Removing water from reaction mixtures due to evaporation and a topochemical reaction increases the yield of esterified 1-germatranol.
- Baryshok, V. P.,Le, G. N. T.
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p. 2430 - 2440
(2022/01/22)
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- Scandium(III) Triflate Catalyzed Direct Synthesis of N-Unprotected Ketimines
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N-Unprotected ketimines are useful substrates and intermediates for synthesizing valuable nitrogen-containing compounds, but their potential applicability is limited by the available synthetic methods. To address this issue, we report a scandium(III) triflate catalyzed direct synthesis of N-unprotected ketimines. Using commercially available reagents and Lewis acid catalysts, ketones were directly transformed into the corresponding N-unprotected ketimines in high yields with broad functional group tolerance, even in multigram scales. The reactions were readily applicable for one-pot synthesis of important compounds such as a glycine Schiff base without isolation of N-unprotected ketimine intermediates. Preliminary mechanistic studies to clarify the reaction mechanism are also described.
- Hirazawa, Yoshinobu,Kadota, Tetsuya,Kondo, Yuta,Morimoto, Hiroyuki,Morisaki, Kazuhiro,Ohshima, Takashi
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p. 120 - 125
(2020/02/20)
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- Novel Si(II)+and Ge(II)+Compounds as Efficient Catalysts in Organosilicon Chemistry: Siloxane Coupling Reaction ?
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Novel catalytically active cationic Si(II) and Ge(II) compounds were synthesized and isolated in pure form. The Ge(II)+-based compounds proved to be stable against air and moisture and therefore can be handled very easily. All compounds efficiently catalyze the oxidative coupling of hydrosil(ox)anes with aldehydes and ketones as oxidation reagents and simultaneously the reductive ether coupling at very low amounts of 0.01 mol %. Because the catalysts also catalyze the reversible cyclotrimerization of aldehydes, paraldehyde can be used as a convenient source for acetaldehyde in siloxane coupling. It is shown that the reaction is especially suitable to make siloxane copolymers. Moreover, a new fluorine-free weakly coordinating boronate anion, B(SiCl3)4-, was successfully combined with the Si(II) and Ge(II) cations to give the stable catalytically active ion pairs Cp*Si:+B(SiCl3)4-, Cp*Ge:+B(SiCl3)4-, and [Cp(SiMe3)3Ge:+]B(SiCl3)4-.
- Fritz-Langhals, Elke,Kneissl, Sotirios,Piroutek, Phillip,Werge, Sven
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- Metal-Organic Framework with Dual Active Sites in Engineered Mesopores for Bioinspired Synergistic Catalysis
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Here we report the design of an enzyme-inspired metal-organic framework (MOF), 1-OTf-Ir, by installing strong Lewis acid and photoredox sites in engineered mesopores. Al-MOF (1), with mixed 2,2′-bipyridyl-5,5-dicarboxylate (dcbpy) and 1,4-benzenediacrylat
- Quan, Yangjian,Song, Yang,Shi, Wenjie,Xu, Ziwan,Chen, Justin S.,Jiang, Xiaomin,Wang, Cheng,Lin, Wenbin
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supporting information
p. 8602 - 8607
(2020/05/13)
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- Direct Conversion of N-Alkylamines to N-Propargylamines through C-H Activation Promoted by Lewis Acid/Organocopper Catalysis: Application to Late-Stage Functionalization of Bioactive Molecules
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An efficient catalytic method to convert an α-C-H bond of N-alkylamines into an α-C-alkynyl bond was developed. In the past, such transformations were carried out under oxidative conditions, and the enantioselective variants were confined to tetrahydroisoquinoline derivatives. Here, we disclose a method for the union of N-alkylamines and trimethylsilyl alkynes, without the presence of an external oxidant and promoted through cooperative actions of two Lewis acids, B(C6F5)3 and a Cu-based complex. A variety of propargylamines can be synthesized in high diastereo-and enantioselectivity. The utility of the approach is demonstrated by the late-stage site-selective modification of bioactive amines. Kinetic investigations that shed light on various mechanistic nuances of the catalytic process are presented.
- Chan, Jessica Z.,Yesilcimen, Ahmet,Cao, Min,Zhang, Yuyang,Zhang, Bochao,Wasa, Masayuki
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supporting information
p. 16493 - 16505
(2020/10/26)
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- Low alkoxy branched siloxane continuous number bath method
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The subject matter of the invention is a continuous method for producing organosiloxanes (O) by reacting silicon compound 1 of general formula 1 RnSiHal4_n (1) and silicon compound 2 which is selected from a silicon compound of general formula 2a or a silicon compound of general formula 2b or mixtures of the silicon compounds of general formulas 2a and 2b R1 3SiHal (2a), R1 3Si-O-SiR1 3 (2b), where R, R1, Hal and n have the meanings described in claim 1, with alcohol and water in the presence of organosiloxane (O) in a reaction unit comprising a distillation column and a vessel (G) which is arranged therebeneath and contains organosiloxane (O), wherein: the content of the vessel is heated to boiling with reflux; silicon compound 1 is introduced into the column above the lower column end; silicon compound 2 is introduced into the vessel (G); the hydrogen halide produced is removed by means of the distillation column; and organosiloxane (O) is continuously withdrawn from the vessel as it is formed, wherein the reaction unit is constantly supplied with silicon compound 1, silicon compound 2, alcohol and water in such quantities that the reaction unit always contains more water than can be consumed by the silicon compound 1 and silicon compound 2 added.
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Paragraph 0090-0101; 0122-0157
(2019/05/15)
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- A six-a base two silicon urea preparation method (by machine translation)
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A six-a base two silicon urea preparation method, the method comprises the following steps: in the presence of an inert gas, in the reactor, adding b [...], then adding six methyl disilazane, adding urea, ammonium chloride or ammonium sulfate and catalyst, heating up to 70 - 90 °C is reacted, the reaction time is 30 - 40 minutes, at the end of the ammonia gas escaping. The reactant is cooled to room temperature, filter, recovery of the precipitation of six a base two silicon urea, then drying under reduced pressure, to obtain the hexa-silicon urea. Collecting the filtrate to apply in the production of the next batch. The method of this invention has a short reaction time, less solvent consumption, the advantage of high stability of the product. (by machine translation)
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Paragraph 0023-0031
(2019/02/06)
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- SYNTHESIS OF ORGANO CHLOROSILANES FROM ORGANOSILANES
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The invention relates to a process for the production of chlorosilanes by subjecting one or more hydndosilanes to the reaction with hydrogen chloride in the presence of at least one ether compound, and a process for the production of such hydndosilanes serving as starting materials.
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Page/Page column 36; 37
(2019/04/16)
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- O-Metalation of silanols and POSS silanols over Amberlyst-15 catalyst: A facile route to unsymmetrical siloxanes, borasiloxanes and germasiloxanes
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A simple and highly practical Amberlyst-catalyzed direct O-metalation of silanols, POSS silanols and alkoxysilanes under mild conditions is proposed. This protocol can be applied to the synthesis of a wide range of important organosilicon derivatives such as siloxanes, germasiloxanes, borasiloxanes and functionalized silsesquioxanes. It is worth noting that Amberlyst-15 can be reused for further experiments and its catalytic activity in this process is well-preserved for several recycling steps.
- Kuciński, Krzysztof,Hreczycho, Grzegorz
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p. 261 - 266
(2019/03/27)
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- Reductive silylation of uranyl mediated by iminosemiquinone ligands
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Stoichiometric silylation of the uranyl species, (dippisq)2UO2THF, which features two reduced iminosemiquinone ligands, is reported. These ligand radicals facilitate the reduction of uranium 6+ to 4+, which is accompanied by silylation of the uranyl moiety with two equivalents of Me3SiBr and release of the oxidized ligand. The intermediate, (Me3SiO)2UBr2(OPPh3)2, is isolated prior to U–O bond cleavage by further addition of Me3SiBr, producing UBr4(OPPh3)2. U–O bond scission can also be performed in a one-pot reaction, by treating (dippisq)2UO2THF with Me2SiCl2, forming UCl4(OPPh3)2 and polymeric silyl products, (O[dbnd]SiMe2)n, with concomitant loss of oxidized ligand. In each case, isotopic 18O labeling experiments highlight the incorporation of the uranyl oxygen atoms into the resulting siloxanes released in the reactions.
- Coughlin, Ezra,Bart, Suzanne C.
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p. 783 - 787
(2019/07/19)
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- Enantioselective Conjugate Azidation of α,β-Unsaturated Ketones under Bifunctional Organocatalysis by Direct Activation of TMSN3
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An enantioselective organocatalytic conjugate azidation of α,β-unsaturated ketones is presented. A bifunctional organocatalyst activates TMSN3, triggering the nucleophilic addition of the azido group to enones in absence of external promoters and avoiding the direct use or the pre-formation of highly toxic and explosive hydrazoic acid. This protocol proceeds with excellent enantiocontrol under mild conditions. DFT calculations and mechanistic trials have been performed in order to demonstrate the direct activation performed by the bifunctional organocatalyst. (Figure presented.).
- Humbrías-Martín, Jorge,Pérez-Aguilar, M. Carmen,Mas-Ballesté, Rubén,Dentoni Litta, Antonella,Lattanzi, Alessandra,Della Sala, Giorgio,Fernández-Salas, Jose A.,Alemán, José
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supporting information
p. 4790 - 4796
(2019/09/16)
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- Metal-Free Catalytic Reductive Cleavage of Enol Ethers
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In contrast to the well-known reductive cleavage of the alkyl-O bond, the cleavage of the alkenyl-O bond is much more challenging especially using metal-free approaches. Unexpectedly, alkenyl-O bonds were reductively cleaved when enol ethers were reacted with Et3SiH and a catalytic amount of B(C6F5)3. Supposedly, this reaction is the result of a B(C6F5)3-catalyzed tandem hydrosilylation reaction and a silicon-assisted β-elimination. A mechanism for this cleavage reaction is proposed based on experiments and density functional theory (DFT) calculations.
- Chulsky, Karina,Dobrovetsky, Roman
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supporting information
p. 6804 - 6807
(2018/11/02)
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- Lewis Base Catalyzed Selective Chlorination of Monosilanes
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A preparatively facile, highly selective synthesis of bifunctional monosilanes R2SiHCl, RSiHCl2 and RSiH2Cl is reported. By chlorination of R2SiH2 and RSiH3 with concentrated HCl/ether solutions, the stepwise introduction of Si?Cl bonds is readily controlled by temperature and reaction time for a broad range of substrates. In a combined experimental and computational study, we establish a new mode of Si?H bond activation assisted by Lewis bases such as ethers, amines, phosphines, and chloride ions. Elucidation of the underlying reaction mechanisms shows that alcohol assistance through hydrogen-bond networks is equally efficient and selective. Remarkably, formation of alkoxysilanes or siloxanes is not observed under moderate reaction conditions.
- Sturm, Alexander G.,Schweizer, Julia I.,Meyer, Lioba,Santowski, Tobias,Auner, Norbert,Holthausen, Max C.
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supporting information
p. 17796 - 17801
(2018/11/23)
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- Preparation method of 1-vinyl-1,1,3,3,3-pentamethyldisiloxane
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The invention relates to a preparation method of 1-vinyl-1,1,3,3,3-pentamethyldisiloxane, prepared by: using 1,3-divinyl-1,1,3,3,-tetramethyldisiloxane ad 1,1,1,3,3,3-hexamethyldisiloxane as materials, carrying out rearrangement reaction under the catalytic action of a complexing catalyst KOH/18-crown ether-6; neutralizing the catalyst, filtering, and distilling filtrate. The macromolecular ring compound 18-crown ether-6 and KOH form the complexing agent; the compound reaction helps improve catalyst activity and efficiently catalyzes for rearrangement reaction. The macromolecular ring compound18-crown ether-6 and KOH form a complexing catalyst; complexing reaction is performed to obtain improved catalyst activity, and rearranging reaction is efficiently catalyzed. In addition, the preparation method is simple, the reacting is fast and stable, and the preparation method has the advantages of high yield, good safety, good environmental friendliness and the like.
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Paragraph 0039-0041
(2018/09/11)
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- meso-tetraaryl(porphyrinato)cobalt(III)-catalyzed oxygenation of disilanes under aerobic conditions
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Cobalt(III) porphyrin-catalyzed oxygenation of disilanes is investigated. Five- and six-membered cyclic disilanes are readily oxygenated, providing the corresponding cyclic disiloxanes in 75%-quant yield. We propose a reaction mechanism involving intermediates with a Co(III)Si bond based on spectroscopic analysis of the reaction mixtures.
- Ohshita, Joji,Matsumura, Yohei,Nakayama, Takahiro,Yoshida, Hiroto,Kunai, Atsutaka,Hisaeda, Yoshio,Hayashi, Takashi
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supporting information
p. 1807 - 1809
(2017/11/23)
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- Synthetic method of hexamethyldisiloxane
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The invention relates to a synthetic method of hexamethyldisiloxane. The method includes the steps that 150 mL of water and 0.3-0.35 moL of sodium hydroxide solid are added into a three-necked flask of 500 mL, the reaction temperature is controlled to be 25-30 DEG C through water bath, the rotating speed of a magnetic stirrer is adjusted to be 1200-1500 rpm, 50 mL of trimethylchlorosilane is slowly added through an injector, reaction solution is taken out after reaction is carried out for 20-25 min, and hexamethyldisiloxane is obtained through cooling, washing, separating and reduced pressure distillation. The synthetic method has the advantages of shortening the reaction time, reducing the reaction temperature, reducing the number of times of washing, omitting the distillation process, simplifying the posttreatment process and increasing the reaction yield to reduce MM production cost.
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Paragraph 0006; 0007; 0008
(2017/02/17)
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- Regiochemistry of Diels-Alder reaction of hexafluorothioacetone and dienes
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The reaction of 2,2,4,4-tetrakis(trifluoromethyl)-dithiethane-1,3 (1) with various hydrocarbon dienes is not regioselective and results in the formation of two isomeric Diels-Alder cycloadducts with the ortho isomer predominating. The reaction of non-conjugated dienes involves ene-insertion of hexafluorothioacetone (HFTA), followed by Diels-Alder reaction of the product of the ene- reaction with a second mole of HFTA, while the reaction of 1,1,4,4-tetramethylbutadiene-1,3 and 2,5-dimethylhexadiene-1,5 results exclusively in HFTA insertion into the allylic C[sbnd]H bond.
- Petrov, Viacheslav A.,Marchione, Alexander A.,Dooley, Rebecca,Marshall, Will
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- DMF-activated chlorosilane chemistry: Molybdenum-catalyzed reactions of R3SiH, DMF and R′3SiCl to initially form R′3SiOSiR′3 and R3SiCl
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The room temperature reactions between R3SiH (R3?=?Et3, PhMe2, Ph2Me) and R′3SiCl (R′3?=?Me3, PhMe2, Ph2Me), with an excess of dimethylformamide (DMF) in the presence of (Me3N)Mo(CO)5 as a catalyst, result in the initial formation of R3SiCl, R′3SiOSiR′3 and Me3N as detected by 29Si, 13C, 1H NMR spectroscopy and GC/MS. As the reaction proceeds, the more so if the reaction temperature is raised, mixed disiloxanes R3SiOSiR′3 and ultimately lesser amounts of R3SiOSiR3 may be detected. A mechanism involving the activation of chlorosilanes by the nucleophilic DMF is proposed to produce transient imminium siloxy ion pairs, [Me2N[dbnd]CHCl]+[R′3SiO]? ? [Me2N[dbnd]CH(OSiR′3)]+Cl? which react with R3SiH to form Me2NCH2OSiR′3 and R3SiCl. A secondary reaction of Me2NCH2OSiR′3 with R′3SiCl produces the symmetrical disiloxane R′3SiOSiR′3 and ClCH2NMe2. The final stage of the reaction is the reduction of ClCH2NMe2 by R3SiH, a reaction which is reported for the first time. The newly created chlorosilane R3SiCl can become involved in the initial DMF activation chemistry thereby forming the other disiloxanes observed as the reaction proceeds.
- Gonzalez, Paulina E.,Sharma, Hemant K.,Pannell, Keith H.
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supporting information
p. 376 - 381
(2017/06/30)
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- Recyclable Trifluoromethylation Reagents from Fluoroform
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We present a strategy to rationally prepare CF3- transfer reagents at ambient temperature from HCF3. We demonstrate that a highly reactive CF3- adduct can be synthesized from alkali metal hydride, HCF3, and borazine Lewis acids in quantitative yield at room temperature. These nucleophilic reagents transfer CF3- to substrates without additional chemical activation, and after CF3 transfer, the free borazine is quantitatively regenerated. These features enable syntheses of popular nucleophilic, radical, and electrophilic trifluoromethylation reagents with complete recycling of the borazine Lewis acid.
- Geri, Jacob B.,Szymczak, Nathaniel K.
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supporting information
p. 9811 - 9814
(2017/08/03)
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- One-Step Synthesis of Siloxanes from the Direct Process Disilane Residue
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The well-established Müller–Rochow Direct Process for the chloromethylsilane synthesis produces a disilane residue (DPR) consisting of compounds MenSi2Cl6?n(n=1–6) in thousands of tons annually. Technologically, much effort is made to retransfer the disilanes into monosilanes suitable for introduction into the siloxane production chain for increase in economic value. Here, we report on a single step reaction to directly form cyclic, linear, and cage-like siloxanes upon treatment of the DPR with a 5 m HCl in Et2O solution at about 120 °C for 60 h. For simplification of the Si?Si bond cleavage and aiming on product selectivity the grade of methylation at the silicon backbone is increased to n≥4. Moreover, the HCl/Et2O reagent is also suitable to produce siloxanes from the corresponding monosilanes under comparable conditions.
- Neumeyer, Felix,Auner, Norbert
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supporting information
p. 17165 - 17168
(2016/11/23)
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- A Palladium(II) Peroxido Complex Supported by the Smallest Steric N-Heterocyclic Carbene, IMe = 1,3-Dimethylimidazole-2-ylidene, and Its Reactivity by Oxygen-Atom Transfer
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Stabilized with an N-heterocyclic carbene ligand of the smallest steric profile, PdII(η2-O2)(IMe)2(IMe = 1,3-dimethylimidazole-2-ylidene) was synthesized by the direct addition of dioxygen to Pd0(IMe)2. The peroxidopalladium complex with IMe, which was previously available only by computation, was characterized by IR spectroscopy and X-ray crystallography. Moreover, its oxygen-atom-transfer reactivity was elucidated by studying its thermolysis in pyridine at 60 °C to yield 1,3-dimethylimidazol-2-one (IMeO) and its reaction with oxygen-atom-transfer acceptors such as PPh3and (Me3Si)2.
- Lee, Eunsung,Bae, Dae Young,Park, Sungho,Oliver, Allen G.,Kim, Yonghwi,Yandulov, Dmitry V.
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supporting information
p. 4561 - 4564
(2016/10/11)
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- Trimethyliodosilane preparation method
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The present invention discloses a trimethyliodosilane preparation method comprising the steps of: 1) in the presence of a protective gas, anion exchange resin and water are added into a reaction vessel, then stirring is started, the reaction vessel is heated to 45 DEG C, trimethyl chlorosilane is added, after the trimethylchlorosilane is added, the reaction vessel is heated to 65-75 DEG C and stirred for 1.5-3 hours for reaction, atmospheric distillation is performed, 99-100 DEG C distillate is collected, dried with anhydrous sodium sulfate, and filtered to obtain hexamethyldisiloxane; 2) in the presence of a protective gas, the hexamethyldisiloxane and aluminum powder are added into another reaction vessel, stirring is started, the reaction vessel is heated to 55 DEG C, elemental iodine is added, after completion of the addition of the elemental iodine, the bath temperature is raised to 120-140 DEG C for reaction and refluxing for 2-3 hours, the device is changed into a distillation apparatus for atmospheric distillation, and 106-107 DEG C distillate is collected to obtain the trimethyliodosilane. The method can improve the yield of the trimethyliodosilane, and is simple in operation, mild in conditions, and suitable for mass production and marketing.
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Paragraph 0023
(2016/11/17)
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- A high-purity high-quality hexamethyl silicone preparation method
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The invention discloses a method for preparing high-purity high-quality hexamethyldisiloxane. The preparation method comprises the following steps: (1) dropwise adding trimethylsilyl chloride to a hydrolysis reaction kettle to which water and a condensation catalyst are added in advance, and carrying out heating reflux; (2) layering the product into a demixer after hydrolysis reaction is finished, wherein the condensation catalyst is at the lowest layer and can be separated and recycled; concentrated acid water is at the middle layer, chlorine hydride can be recovered by a hydrochloric acid analysis technology; a hydrolysate at the upper layer is washed with water and neutralized to neutral by using a carbonate solution, an oil phase is separated out of the hydrolysate at the upper layer after the hydrolysate at the upper layer is washed with water for a plurality of times; (3) removing water from the oil phase separated in the step (2) by using a water removal agent, stirring and filtering; (4) fractionating and collecting fraction with the temperature of 99-102 DEG C, so as to obtain the hexamethyldisiloxane of which the purity is greater than 99.9% (mass fraction). The preparation method disclosed by the invention has the advantages that the reaction speed is high, the utilization rate of trimethylsilyl chloride is high and the yield and quanlity of hexamethyldisiloxane are high.
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Paragraph 0025-0029
(2017/03/08)
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- Reductive silylation of Cp?UO2(MesPDIMe) promoted by Lewis bases
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Functionalization of the uranyl moiety (UO22+) in Cp?UO2(MesPDIMe) (1-PDI) (MesPDIMe = 2,6-((Mes)NCMe)2C5H3N; Mes = 2,4,6-triphenylmethyl), which bears a reduced, monoanionic pyridine(diimine) ligand, is reported. Silylating reagents, R3Si-X (R = Me, X = Cl, I, OTf, SPh; R = Ph, X = Cl), effectively add across the strong OUO bonds in the presence of the Lewis base, OPPh3, generating products of the form (R3SiO)2UX2(OPPh3)2 (R = Me, X = I (2-OPPh3), Cl (3-OPPh3), SPh (5-OPPh3), OTf (6-OPPh3); R = Ph, X = Cl (4-OPPh3)). During this transformation, reduction to uranium(iv) occurs with loss of (Cp?)2 and MesPDIMe, each of which acts as a one-electron source. In the reaction, the Lewis base serves to activate the silyl halide, generating a more electrophilic silyl group, as determined by 29Si NMR spectroscopy, that undergoes facile transfer to the oxo groups. Complete U-O bond scission was accomplished by treating the uranium(iv) disiloxide compounds with additional silylating reagent, forming the family (Ph3PO)2UX4. All compounds were characterized by 1H NMR, infrared, and electronic absorption spectroscopies. X-ray crystallographic characterization was used to elucidate the structures of 2-OPPh3, 4-OPPh3, 5-OPPh3, and 6-OPPh3.
- Kiernicki,Harwood,Fanwick,Bart
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p. 3111 - 3119
(2016/02/20)
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- Method of manufacturing polyimidesiloxane compd. (by machine translation)
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PROBLEM TO BE SOLVED: rhodium, platinum, and palladium complex or the like instead of the catalyst is found, to provide a new method for manufacturing polyimidesiloxane compd. ~~~ a SOLUTION: and in the condensation reaction silanolated hydrosilane, nickel compound represented by the following eq. (C) is used as a catalyst, siloxane compound can be produced. [And 1] ( In the formula, R 3 are each independently a hydrogen atom, or a nitrogen atom, an oxygen atom, a sulfur atom, a silicon atom, phosphorus atom, and a halogen atom is selected from the group consisting of at least 1 may also include a kind of carbon number 1-20 hydrocarbon group. ) Selected drawing: no (by machine translation)
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Paragraph 0027; 0028
(2016/11/17)
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- Glycosylation intermediates studied using low temperature 1H- and 19F-DOSY NMR: New insight into the activation of trichloroacetimidates
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Low temperature 1H- and 19F-DOSY have been used for analyzing reactive intermediates in glycosylation reactions, where a glycosyl trichloroacetimidate donor has been activated using different catalysts. The DOSY protocols have been optimized for low temperature experiments and provided new insight into acid catalyzed glycosylation chemistry. From the study a new glycosylation intermediate was characterized.
- Qiao, Yan,Ge, Wenzhi,Jia, Lingyu,Hou, Xianglin,Wang, Yingxiong,Pedersen, Christian M.
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p. 11418 - 11421
(2016/09/23)
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- Mechanism of Molybdenum-Mediated Carbon Monoxide Deoxygenation and Coupling: Mono- and Dicarbyne Complexes Precede C-O Bond Cleavage and C-C Bond Formation
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Deoxygenative coupling of CO to value-added C≥2 products is challenging and mechanistically poorly understood. Herein, we report a mechanistic investigation into the reductive coupling of CO, which provides new fundamental insights into a multielectron bond-breaking and bond-making transformation. In our studies, the formation of a bis(siloxycarbyne) complex precedes C-O bond cleavage. At -78 °C, over days, C-C coupling occurs without C-O cleavage. However, upon warming to 0 °C, C-O cleavage is observed from this bis(siloxycarbyne) complex. A siloxycarbyne/CO species undergoes C-O bond cleavage at lower temperatures, indicating that monosilylation, and a more electron-rich Mo center, favors deoxygenative pathways. From the bis(siloxycarbyne), isotopic labeling experiments and kinetics are consistent with a mechanism involving unimolecular silyl loss or C-O cleavage as rate-determining steps toward carbide formation. Reduction of Mo(IV) CO adducts of carbide and silylcarbyne species allowed for the spectroscopic detection of reduced silylcarbyne/CO and mixed silylcarbyne/siloxycarbyne complexes, respectively. Upon warming, both of these silylcarbynes undergo C-C bond formation, releasing silylated C2O1 fragments and demonstrating that the multiple bonded terminal Mo≡C moiety is an intermediate on the path to deoxygenated, C-C coupled products. The electronic structures of Mo carbide and carbyne species were investigated quantum mechanically. Overall, the present studies establish the elementary reactions steps by which CO is cleaved and coupled at a single metal site.
- Buss, Joshua A.,Agapie, Theodor
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supporting information
p. 16466 - 16477
(2016/12/27)
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- Metal-Mediated Production of Isocyanates, R3EN=C=O from Dinitrogen, Carbon Dioxide, and R3ECl
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A highly efficient and versatile chemical cycle has been developed for the production of isocyanates through the molecular fixation of N2, CO2 and R3ECl (E=C, Si, and Ge). Key steps include a 'one-pot' photolytic N-N bond cleavage of a Group6 dinuclear dinitrogen complex with insitu trapping by R3ECl to provide a metal terminal imido complex that can engage in simultaneous nitrene-group transfer and oxygen-atom transfer to generate an intermediate metal terminal oxo complex with release of the isocyanate product. Reaction of the oxo complex with additional equivalents of R3ECl regenerates a metal dichloride that is the precursor for dinuclear dinitrogen starting material.
- Keane, Andrew J.,Farrell, Wesley S.,Yonke, Brendan L.,Zavalij, Peter Y.,Sita, Lawrence R.
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supporting information
p. 10220 - 10224
(2015/09/01)
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- Synthesis of an [(NHC)2Pd(SiMe3)2] complex and catalytic cis-bis(silyl)ations of alkynes with unactivated disilanes
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The novel complex cis-[(ITMe)2Pd(SiMe3)2 (ITMe=1,3,4,5-tetramethylimidazol-2-ylidene) has been synthesized by mild oxidative cleavage of Me3SiSiMe3 using [(ITMe)2Pd0]. The use of this complex as precatalyst for the cis-bis(silyl)ation of alkynes using unactivated disilanes is reported. Double the Si: The novel complex cis-[(ITMe)2Pd(SiMe3)2] (1, ITMe=1,3,4,5-tetramethylimidazol-2-ylidene) has been synthesized by mild oxidative cleavage of Me3SiSiMe3 using [(ITMe)2Pd0]. The synthesized complex was used as a precatalyst for the cis-bis(silyl)ation of alkynes using unactivated disilanes.
- Ansell, Melvyn B.,Roberts, Debbie E.,Cloke, F. Geoffrey N.,Navarro, Oscar,Spencer, John
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supporting information
p. 5579 - 5582
(2015/09/21)
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- Combined effect of ether and siloxane substituents on imidazolium ionic liquids
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Ionic liquids (ILs) in combination with ether and siloxane substituents on the imidazolium cation, comprising of bis(trifluoromethylsulfonyl)imide (NTf2) anions, have been synthesized due to their low viscosities, high thermal stabilities and low melting or glass transition temperatures(Tg). The structural flexibility of the ether and siloxane substituents on the imidazolium center overcomes the effect of van der Waals forces and gives them desirable and unique physical properties. These novel ILs show low viscosities (～72 mPa s at 25 °C), high thermal stabilities up to 430°C, and a wide liquid range over 500°C. In addition, these ILs exhibit only an amorphous glassy state on cooling at Tg below -74°C and cannot order properly to afford crystallization. The detailed thermal stability, phase transitions and heat capacity were studied by TGA, DSC and temperature-modulated DSC analysis. More importantly, we have also reported the large-scale (one kilogram) microwave-assisted synthesis of ILs [BMIM]Br and [1O2O2-Im-2O1]I as efficient and greener processes.
- Chavan, Santosh N.,Mandal, Debaprasad
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p. 64821 - 64831
(2015/08/18)
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- Reactions of hydroxyl-containing compounds with tert-butyl hydroperoxide in the presence of chromium tetra-tert-butoxide
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Primary and secondary aliphatic, alkylaromatic, cyclic, and organoelement alcohols are efficiently oxidized by tert-butyl hydroperoxide in the presence of both equimolar and catalytic quantities of chromium tetra-tert-butoxide (C6H6, 20°C). α-Diols containing tertiary hydroxyl groups interact with this system via oxidative splitting of the carbon scaffold. The oxidation includes the stages of formation and decomposition of chromium-containing peroxy compounds. Further transformations of the carbonyl compounds depend on the structure of radicals in the molecules.
- Stepovik,Zaburdaeva,Fukin,Karaghiosoff
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p. 2547 - 2559
(2015/12/30)
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- An efficient method for the preparation of silyl esters of diphosphoric, phosphoric, and phosphorous acid
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Tetrakis(trialkylsilyl) diphosphate (alkyl = Me, Et, iPr, tBu) can be obtained in quantitative yield by reacting commercial disodium dihydrogen diphosphate with the respective trialkyl chlorosilane in a triphasic system with formamide. The alkylsilane residues of the diphosphate silyl esters can be either partially or completely hydrolyzed without concurrent cleavage of the P-O-P bond of the diphosphate moiety. The method can be expanded to efficiently produce other persilylated or partially silylated phosphates and phosphites.
- Wessjohann, Ludger A.,Dessoy, Marco A.
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p. 133 - 137
(2014/02/14)
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- Efficient fluoride-catalyzed conversion of CO2 to CO at room temperature
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A protocol for the efficient and selective reduction of carbon dioxide to carbon monoxide has been developed. Remarkably, this oxygen abstraction step can be performed with only the presence of catalytic cesium fluoride and a stoichiometric amount of a disilane in DMSO at room temperature. Rapid reduction of CO2 to CO could be achieved in only 2 h, which was observed by pressure measurements. To quantify the amount of CO produced, the reduction was coupled to an aminocarbonylation reaction using the two-chamber system, COware. The reduction was not limited to a specific disilane, since (Ph 2MeSi)2 as well as (PhMe2Si)2 and (Me3Si)3SiH exhibited similar reactivity. Moreover, at a slightly elevated temperature, other fluoride salts were able to efficiently catalyze the CO2 to CO reduction. Employing a nonhygroscopic fluoride source, KHF2, omitted the need for an inert atmosphere. Substituting the disilane with silylborane, (pinacolato)BSiMe2Ph, maintained the high activity of the system, whereas the structurally related bis(pinacolato)diboron could not be activated with this fluoride methodology. Furthermore, this chemistry could be adapted to 13C-isotope labeling of six pharmaceutically relevant compounds starting from Ba13CO 3 in a newly developed three-chamber system.
- Lescot, Camille,Nielsen, Dennis U.,Makarov, Ilya S.,Lindhardt, Anders T.,Daasbjerg, Kim,Skrydstrup, Troels
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supporting information
p. 6142 - 6147
(2014/05/20)
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- Synthetic methods and intermediates for the preparation of xenicanes
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The invention provides novel synthetic intermediates and synthetic methods that are useful for preparing compounds of the xenicane family. Certain compounds of the invention may also possess anti-cancer properties.
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Page/Page column
(2014/09/03)
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