16286-54-7Relevant academic research and scientific papers
Silylation of Alcohols, Phenols, and Silanols with Alkynylsilanes – an Efficient Route to Silyl Ethers and Unsymmetrical Siloxanes
Kuciński, Krzysztof,Stachowiak, Hanna,Hreczycho, Grzegorz
, p. 4042 - 4049 (2020/07/04)
The formation of several silyl ethers (alkoxysilanes, R3Si-OR') and unsymmetrical siloxanes (R3Si-O-SiR'3) can be catalyzed by the commercially available potassium bis(trimethylsilyl)amide (KHMDS). The reaction proceeds via direct dealkynative coupling between various alcohols or silanols and alkynylsilanes, with a simultaneous formation of gaseous acetylene as the sole by-product. The dehydrogenative and dealkenative coupling of alcohols or silanols are well-investigated, whilst the utilization of alkynylsilanes as silylating agents has never been comprehensively studied in this context. Overall, the presented system allows the synthesis of various attractive organosilicon compounds under mild conditions, making this approach an atom-efficient, environmentally benign, and sustainable alternative to existing synthetic solutions.
Differentiation of isomeric cresols by silylation in combination with gas chromatography/mass spectrometry analysis
Xu, Jiaxiang,Zhu, Guohua,Zhang, Huarong,Liu, Jinsong,Jiang, Kezhi
, (2020/01/21)
Rationale: m-Cresol is listed as a priority controlled contaminant in many countries, but it is very difficult to accurately determine isomeric cresols due to their incomplete chromatographic separation on commercially available chromatographic columns and their nearly identical mass spectra. Methods: Silylation of isomeric cresols was carried out by treatment with N-methyl-N-(trimethylsilyl)trifluoroacetamide. The formed trimethyl(tolyloxy)silanes were analyzed by gas chromatography/mass spectrometry (GC/MS). Theoretical calculations were carried out with the Gaussian 03 program using the density functional theory (DFT) method at the B3LYP/6-311 + G(2d,p) level. Results: The derivatives of three isomeric cresols and six isomeric xylenols have been completely separated on an HP-5MS capillary column within a GC run of only 10 minutes. In addition, the derivative o-cresol can be very easily differentiated from its isomers due to its characteristic base peak ion at m/z 91 in electron ionization (EI)-MS. DFT calculation results indicated that the formation of the abundant fragment ion at m/z 91 is attributed to a facile dissociation pathway involving the shift of a neighboring phenylmethyl hydrogen atom in EI-MS of trimethyl(o-tolyloxy)silane. Conclusions: Silylation provides a promising solution for simultaneous determination of isomeric cresols and isomeric xylenols.
Regioselectivity of Hydroxyl Radical Reactions with Arenes in Nonaqueous Solutions
Moores, Lee C.,Kaur, Devinder,Smith, Mathew D.,Poole, James S.
, p. 3260 - 3269 (2019/03/11)
The regioselectivity of hydroxyl radical addition to arenes was studied using a novel analytical method capable of trapping radicals formed after the first elementary step of reaction, without alteration of the product distributions by secondary oxidation processes. Product analyses of these reactions indicate a preference for o- over p-substitution for electron donating groups, with both favored over m-addition. The observed distributions are qualitatively similar to those observed for the addition of other carbon-centered radicals, although the magnitude of the regioselectivity observed is greater for hydroxyl. The data, reproduced by high accuracy CBS-QB3 computational methods, indicate that both polar and radical stabilization effects play a role in the observed regioselectivities. The application and potential limitations of the analytical method used are discussed.
Insertion of CO2 and COS into Bi-C bonds: Reactivity of a bismuth NCN pincer complex of an oxyaryl dianionic ligand, [2,6-(Me 2NCH2)2C6H3]Bi(C 6H2tBu2O)
Kindra, Douglas R.,Casely, Ian J.,Fieser, Megan E.,Ziller, Joseph W.,Furche, Filipp,Evans, William J.
, p. 7777 - 7787 (2013/07/19)
The reactivity of the unusual oxyaryl dianionic ligand, (C 6H2tBu2-3,5-O-4)2-, in the Bi3+ NCN pincer complex Ar′Bi(C6H 2tBu2-3,5-O-4), 1, [Ar′ = 2,6-(Me 2NCH2)2C6H3] has been explored with small molecule substrates and electrophiles. The first insertion reactions of CO2 and COS into Bi-C bonds are observed with this oxyaryl dianionic ligand complex. These reactions generate new dianions that have quinoidal character similar to the oxyaryl dianionic ligand in 1. The oxyarylcarboxy and oxyarylthiocarboxy dianionic ligands were identified by X-ray crystallography in Ar′Bi[O2C(C6H2 tBu2-3-5-O-4)-κ2O,O′], 2, and Ar′Bi[OSC(C6H2tBu2-3-5-O-4)- κ2O,S], 3, respectively. Silyl halides and pseudohalides, R3SiX (X = Cl, CN, N3; R = Me, Ph), react with 1 by attaching X to bismuth and R3Si to the oxyaryl oxygen to form Ar′Bi(X)(C6H2tBu2-3,5- OSiR3-4) complexes, a formal addition across five bonds. These react with additional R3SiX to generate Ar′BiX2 complexes and R3SiOC6H3tBu2-2,6. The reaction of 1 with I2 forms Ar′BiI2 and the coupled quinone, 3,3′,5,5′-tetra-tert-butyl-4,4′- diphenoquinone, by oxidative coupling.
Lanthanum trichloride: An efficient catalyst for the silylation of hydroxyl groups by activating hexamethyldisilazane (HMDS)
Narsaiah, Akkirala Venkat
, p. 3614 - 3618 (2008/02/08)
A variety of hydroxy functional groups was protected as their corresponding trimethylsilyl ethers using HMDS in the presence of lanthanum trichloride. The catalyst LaCl3 activates the HMDS and accelerates the reaction under mild reaction conditions at room temperature to afford the corresponding silylated products in excellent yields.
Simple and practical protocol for the silylation of phenol derivatives using reusable NaHSO4 dispread on silica gel under neutral conditions
Khalili, Mahideh S.,Ghafuri, Hossein,Mojahedi-Jahromi, Samaneh,Hashemi, Mohammed M.
, p. 175 - 179 (2007/10/03)
A simple and mild procedure for the trimethylsilylation of a wide variety of phenols with hexamethyldisilazane (HMDS) on the surface of silica gel dispersed with NaHSO4 at r.t. in a few minutes with excellent yields under neutral conditions is
Silica sulfuric acid as a reusable catalyst for efficient and simple silylation of hydroxyl groups using hexamethyldisilazane (HMDS)
Ghafuri, Hossein,Eftekhari-Sis, Bagher,Hashemi, Mohammed M.
, p. 1645 - 1651 (2008/02/08)
At room temperature, alcohols and phenols are efficiently protected with hexamethyldisilazane (HMDS) in the presence of silica sulfuric acid in good to excellent yields. The catalyst can be recycled for subsequent reactions without any appreciable loss of efficiency. Copyright Taylor and Francis Group, LLC.
Indium tribromide: An efficient catalyst for the silylation of hydroxy groups by the activation of hexamethyldisilazane
Yadav,Reddy,Basak,Baishya,Venkat Narsaiah
, p. 3831 - 3834 (2008/02/10)
A variety of substrates containing hydroxy groups have been protected as their corresponding trimethylsilyl ethers using 1,1,1,3,3,3-hexamethyldisilazane in the presence of indium tribromide. The catalyst indium tribromide activates the 1,1,1,3,3,3-hexamethyldisilazane and accelerates the reaction under mild reaction conditions at room temperature. Georg Thieme Verlag Stuttgart.
Reaction courses for formation of early transition metal phenoxides
Yasuda, Hajime,Nakayama, Yuushou,Takei, Kazuo,Nakamura, Akira,Kai, Yasushi,Kanehisa, Nobuko
, p. 105 - 116 (2007/10/02)
The 1 : 1 and 1 : 2 reactions of TiCl4 with Me3SiO-2,6-(CH3)2C6H3 produced TiCl32(THF)2 (1) and TiCl22(THF)2 (2), respectively, bearing six-coordinated geometry around Ti.The compound 2 assumes the cis-geometry regarding the two phenoxy groups and THF is coordinated in the trans position of the phenoxy groups.Similarly, the 1 : 1 and 1 : 2 reactions of NbCl5 with the trimethylsilylphenyl ether provided NbCl42(THF) (7) and NbCl32(THF) (8), respectively, with octahedron structure.The THF molecule again locates in the trans position of a phenoxy group in both cases and the two phenoxy groups of 8 locate in the cis position.Tungsten mono-phenoxide, WCl52 (12), also has octahedron structure.In cases of tungsten bis-phenoxides, WCl42 (13) and WCl42 (14), the former has trans structure while the latter has cis structure regarding the phenoxy groups.A unique square pyramidal geometry has been observed in the tetrakis(phenoxy) tungsten, WCl4 (16).Key words: Titanium; Niobium; Tungsten; Zirconium; Tantalum
Unique Molecular Structures of Tungsten Phenoxides
Kanehisa, Nobuko,Kai, Yasushi,Kasai, Nobutami,Yasuda, Hajime,Nakayama, Yuushou,Nakamura, Akira
, p. 1197 - 1201 (2007/10/02)
As a series of structural chemistry of early transition metal-phenoxides, the molecular structures of WCl5 (1) and WCl42 (2) have been determined by an X-ray diffraction method.Crystal data: 1; orthorombic, space group Cm
