- A NEW REDUCTIVE SILYLATION OF p-QUINONES WITH HEXAMETHYLDISILANE CATALYZED BY IODINE
-
In the presence of a catalytic amount of iodine, hexamethyldisilane can reductively silylate p-quinones under mild conditions to afford 1,4-bis(trimethylsiloxy)arenes in high yields.
- Matsumoto, Hideyuki,Koike, Shunji,Matsubara, Ikuya,Nakano, Taichi,Nagai, Yoichiro
-
-
Read Online
- Rice husk: Introduction of a green, cheap and reusable catalyst for the protection of alcohols, phenols, amines and thiols
-
A mild, efficient and eco-friendly protocol for the chemoselective protection of benzylic and primary and less hindered secondary aliphatic alcohols and phenols as trimethylsilyl ethers and different types of amines as N-tert-butylcarbamates is developed using rice husk (RiH) as the catalyst. This reagent is also able to catalyze the acetylation of alcohols, phenols, thiols and amines with acetic anhydride. Easy work-up, relatively short reaction times, excellent yields and low cost, availability and reusability of the catalyst are the striking features of this methodology, which can be considered to be one of the best and general methods for the protection of alcohols, phenols, thiols and amines. In addition, the use of a green reagent in the above-mentioned reactions results in a reduction of environmental pollution and of the cost of the applied methods.
- Shirini, Farhad,Akbari-Dadamahaleh, Somayeh,Mohammad-Khah, Ali,Aliakbar, Ali-Reza
-
p. 164 - 170
(2014/03/21)
-
- Rice husk ash: A new, cheap, efficient, and reusable reagent for the protection of alcohols, phenols, amines, and thiols
-
Amild, efficient, and eco-friendly protocol for the protection of alcohols and phenols as trimethylsilyl ethers has been developed using rice husk ash as a reagent. This reagent is also able to catalyze the acetylation of alcohols, phenols, thiols, and amines with acetic anhydride. All reactions were performed under mild conditions in good to high yields. Copyright
- Shirini,Akbari-Dadamahaleh, Somayeh,Mohammad-Khah, Ali
-
p. 577 - 586
(2014/06/09)
-
- Preparation, characterization and use of 1,3-disulfonic acid imidazolium hydrogen sulfate as an efficient, halogen-free and reusable ionic liquid catalyst for the trimethylsilyl protection of hydroxyl groups and deprotection of the obtained trimethylsilanes
-
Novel 1,3-disulfonic acid imidazolium hydrogen sulfate, a halogen-free ionic liquid, is a recyclable and eco-benign catalyst for the trimethylsilyl protection of hydroxyl groups at room temperature under solvent free conditions to afford trimethylsilanes in excellent yields (92-100%) and in very short reaction times (1-5 min). Deprotection of the resulting trimethylsilanes can also be achieved using the same catalyst in methanol. The catalyst was characterized by IR, 1H NMR, 13C NMR and MS studies. All the products were extensively characterized by IR, 1H NMR, MS, and elemental and melting point analyses. This new method consistently has the advantages of excellent yields and short reaction times. Further, the catalyst can be recovered and reused for several times without loss of activity. The work-up of the reaction consists of a simple separation, followed by concentration of the crude product and purification.
- Shirini, Farhad,Khaligh, Nader Ghaffari,Akbari-Dadamahaleh, Somayeh
-
-
- Highly efficient and chemoselective trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) catalyzed by reusable electron-deficient [TiIV(salophen)(OTf)2]
-
In the present work, highly efficient trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) catalyzed by high-valent [Ti IV(salophen)(OTf)2] is reported. Under these conditions, primary, secondary and tertiary alcohols as well as phenols were silylated in short reaction times and high yields. It is noteworthy that this method can be used for chemoselective silylation of primary alcohols in the presence of secondary and tertiary alcohols and phenols. The catalyst was reused several times without loss of its catalytic activity.
- Yadegari, Maryam,Moghadam, Majid,Tangestaninejad, Shahram,Mirkhani, Valiollah,Mohammadpoor-Baltork, Iraj
-
experimental part
p. 332 - 338
(2012/03/12)
-
- Highly efficient and selective trimethylsilylation of alcohols and phenols with hexamethyldisilazane catalyzed by polystyrene-bound tin(IV) porphyrin
-
In the present work, investigation of the catalytic activity of tetrakis(p-aminophenyl)porphyrinatotin(IV) trifluoromethanesulfonate, [Sn IV(TNH2PP)(OTf)2], supported on chloromethylated polystyrene in the trimethylsilylation of alcohols and phenols with hexamethyldisilazane is reported. The prepared catalyst was characterized by elemental analysis, FT-IR and diffuses reflectance UV-Vis spectroscopic methods. This catalyst was used for selective trimethylsilylation of different alcohols and phenols with HMDS, with short reaction times and high yields. Also the catalyst is of high reusability and stability, in that it was recovered several times without loss of its initial activity.
- Gharaati, Shadab,Moghadam, Majid,Tangestaninejad, Shahram,Mirkhani, Valiollah,Mohammadpoor-Baltork, Iraj
-
experimental part
p. 87 - 95
(2012/05/05)
-
- Preparation, characterization and use of 3-methyl-1-sulfonic acid imidazolium hydrogen sulfate as an eco-benign, efficient and reusable ionic liquid catalyst for the chemoselective trimethylsilyl protection of hydroxyl groups
-
New and novel ionic liquid (3-methyl-1-sulfonic acid imidazolium hydrogen sulfate) is a recyclable and eco-benign catalyst for the chemoselective trimethylsilyl protection of hydroxyl groups under solvent-free conditions to afford trimethylsilanes in excellent yields (92-100%) and in very short reaction times (1-8 min). The catalyst was characterized by FT-IR, 1H NMR and 13C NMR studies. All the products were extensively characterized by 1H NMR, IR, GC-MS and melting point analyses. A mechanism for the catalytic activity is proposed. The catalyst can be recovered and reused without loss of activity. The work-up of the reaction consists of a simple separation, followed by concentration of the crude product and purification.
- Khaligh, Nader Ghaffari
-
experimental part
p. 63 - 70
(2011/12/02)
-
- Succinimide-N-sulfonic acid: A mild, efficient, and reusable catalyst for the chemoselective trimethylsilylation of alcohols and phenols
-
Succinimide-N-sulfonic acid (SuSA) is easily prepared by the reaction of succinimide with chlorosulfonic acid. This reagent is able to efficiently catalyze the chemoselective trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS). All reactions were performed under mild reaction conditions, giving excellent yields. Copyright Taylor & Francis Group, LLC.
- Shirini,Khaligh, Nader Ghaffari
-
experimental part
p. 2156 - 2165
(2012/04/10)
-
- Protection of hydroxyl groups as a trimethylsilyl ether by 1,1,1,3,3,3-hexamethyldisilazane promoted by aspartic acid as an efficient organocatalyst
-
A wide variety of alcohols and phenols were protected as trimethylsilyl ethers using 1,1,1,3,3,3-hexamethyl disilazane catalyzed by aspartic acid as a non-toxic, metal-free, and green organocatalyst at room temperature in acetonitrile under mild and heterogeneous conditions. The procedure is operationally simple and the silylated product was obtained in high yield and purity.
- Ghorbani-Choghamarani, Arash,Norouzi, Masoomeh
-
scheme or table
p. 595 - 598
(2012/01/06)
-
- Nanocrystalline TiO2 as an efficient and reusable catalyst for the chemoselective trimethylsilylation of primary and secondary alcohols and phenols
-
Nanocrystalline TiO2 was used as an efficient and recyclable catalyst for the chemoselective trimethylsilylation of primary and less hindered secondary alcohols and phenols with hexamethyldisilazane (HMDS). All reactions were performed under mild and completely heterogeneous conditions in good to excellent yields.
- Shirini, Farhad,Khoshdel, Meysam Alipour,Abedini, Masoumeh,Atghia, Seyyed Vahid
-
experimental part
p. 1211 - 1214
(2012/01/04)
-
- Electron-deficient vanadium(IV) tetraphenylporphyrin: A new, highly efficient and reusable catalyst for chemoselective trimethylsilylation of alcohols and phenols with hexamethyldisilazane
-
In the present work, the application of electron-deficient tetraphenylporphyrinatovanadium(IV) trifluoromethanesulfonate, [V IV(TPP)(OTf)2], in the trimethylsilylation of alcohols and phenols with hexamethydisilazane (HMDS) is reported. This new V(IV) catalyst was used as an efficient catalyst for silylation of not only primary alcohols but also sterically hindered secondary and tertiary alcohols with HMDS. Trimethylsilylation of phenols with HMDS was also performed to afford the desired Trimethylsilyl ethers (TMS) ethers. The chemoselectivity of this method was also investigated. This catalyst can be reused several times without loss of its activity. Copyright
- Moghadam, Majid,Mohammadpoor-Baltork, Iraj,Tangestaninejad, Shahram,Mirkhani, Valiollah,Khosropour, Ahmad Reza,Taghavi, S. Abdolmanaf
-
experimental part
p. 687 - 694
(2012/01/06)
-
- Partition coefficients of ketones, phenols, aliphatic and aromatic acids, and esters in n-hexane/nitromethane
-
Liquid-liquid partition is used in sample preparation and in countercurrent and liquid-liquid chromatographic separations. Partition coefficients are widely used in toxicology, environmental, and analytical chemistry. The K hn determination procedure for the n-hexane/ nitromethane system was optimized and partition coefficients for 99 ketones, esters and trimethylsilyl derivatives of phenols, aliphatic and aromatic acids were determined. For 130 compounds, Khn values were predicted using mathematical relationships between Khn and other physicochemical and structural parameters. Versita Sp. z o.o.
- Kotowska, Urszula,Isidorov, Valery A.
-
scheme or table
p. 813 - 824
(2012/03/27)
-
- [SnIV(TPP)(BF4)2]: An efficient and reusable catalyst for chemoselective trimethylsilylation of alcohols and phenols with hexamethyldisilazane
-
Tin(IV)tetraphenylporphyrinato tetrafluoroborate, [SnIV(TPP)(BF4)2], was used as an efficient catalyst for trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS). High-valent [SnIV(TPP)(BF4)2] catalyzes trimethylsilylation of primary, secondary and tertiary alcohols as well as phenols, and the corresponding TMS-ethers were obtained in high yields and short reaction times at room temperature. While, under the same reaction conditions [SnIV(TPP)Cl2] is less efficient to catalyze these reactions. One important feature of this catalyst is its ability in the chemoselective silylation of primary alcohols in the presence of secondary and tertiary alcohols and phenols. The catalyst was reused several times without loss of its catalytic activity.
- Moghadam, Majid,Tangestaninejad, Shahram,Mirkhani, Valiollah,Mohammadpoor-Baltork, Iraj,Gharaati, Shadab
-
experimental part
p. 212 - 219
(2010/04/04)
-
- Fe(HSO4)3 promoted trimethylsilylation of alcohols and phenols in solution and under solvent-free conditions
-
Alcohols and phenols are efficiently converted to their corresponding trimethylsilyl ethers with hexamethyldisilazane (HMDS) in the presence of Fe(HSO4)3 in solution and under solvent-free conditions.
- Shirini, Farhad,Zolfigol, Mohammad A.,Abri, Abdol-Reza
-
-
- Rapid and highly efficient trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) catalyzed by reusable zirconyl triflate, [ZrO(OTf)2]
-
In this paper, rapid and efficient trimethylsilylation of alcohols and phenols with hexamethyldisilazane in the presence of catalytic amounts of ZrO(OTf)2 is reported. Primary, secondary and tertiary alcohols as well as phenols were efficiently converted to their corresponding TMS ethers in short reaction times at room temperature. It is noteworthy that this method can be used for chemoselective silylation of primary alcohols in the presence of secondary and tertiary alcohols and phenols.
- Moghadam, Majid,Tangestaninejad, Shahram,Mirkhani, Valiollah,Mohammadpoor-Baltork, Iraj,Chahardahcheric, Shahin,Tavakoli, Ziba
-
p. 2041 - 2046
(2008/09/19)
-
- Sulfuric acid supported on silica gel: An efficient catalyst for silylation of hydroxyl groups with HMDS and their convenient deprotection under non-aqueous condition
-
A mild and efficient silylation of alcohols and phenols with hexamethyl-disilazane(HMDS) and convenient desilylation of the corresponding silyl ethers are achieved using a catalytic amount of H2SO4 SiO2 under non-aqueous condition. In this work chemoselective silylation of hydroxy compounds in the presence of thiols and amines is conducted.
- Lakouraj,Akbari
-
p. 1165 - 1167
(2007/10/03)
-
- Highly efficient and chemoselective reductive bis-silylation of quinones by silyltellurides
-
(matrix presented) Silyltellurides serve as new silicon-based chemoselective reducing agents and reduce quinones to the corresponding bis-silylated hydroquinones. The reaction proceeds under ambient thermal conditions without the need of any additional promoters or catalysts and gives the products in excellent yields. Several control experiments suggest that the reaction is initiated by a single electron transfer from silyltellurides to quinones.
- Yamago, Shigeru,Miyazoe, Hiroshi,Iida, Kazunori,Yoshida, Jun-Ichi
-
p. 3671 - 3673
(2007/10/03)
-
- Structures of Sterically Overcrowded Molecules 39. Single Crystal and Gas Phase Structures of 1,4-Bis(trimethylsiloxy)benzene
-
1,4-Bis(trimethylsiloxy)benzene has been crystallized both by vacuum sublimation and from n-heptane solution, which each yielded colourless plates with identical monoclinic unit cell dimensions (P21/n, Z = 4).The conformation of C1 symmetry shows the two (H3C)3SiO-substituents to be conrotationally twisted around the O-(C6H4)-O axis by dihedral angles of +/- 60 deg.According to the photoelectron spectroscopic ionisation pattern and its Koopmans' assignment, IEVn = -εJAM 1, by AM 1 eigenvalues, the gas phase structure should also be of C1 symmetry.The results of geometry-optimized MNDO, AM 1 or PM 3 calculations for the monosubstituted derivative H5C6-OSi(CH3)3 are compared with respect to the quality of their fit to the measured data. - Keywords: Sterically Overcrowded Organosilicon Molecules, Single Crystal Structure, Photoelectron Spectroscopy, Quantum Chemical Calculations
- Bock, H.,Meuret, J.,Bats, J.W.,Havlas, Z.
-
p. 288 - 296
(2007/10/02)
-
- Alkylation of Quinones by O-Silylated Ketene Acetals in LiClO4/Ether as Reaction Medium
-
O-Silylated ketene acetals (2, 5) undergo 1,4-conjugative addition to α,β-unsaturated carbonyl systems of quinones 1 in the presence of lithium perchlorate in ether to form 2(3H)-benzofuranones 3.Key Words: Quinones / Ketene acetals, O-silylated / Mukaiyama reaction / 2(3H)-Benzofuranone / Homogentisic acid
- Ipaktschi, Junes,Heydari, Akbar
-
p. 1513 - 1516
(2007/10/02)
-
- ORGANIC SONOCHEMISTRY, ULTRASONIC ACCELERATION OF THE REACTION OF DICARBONYLS WITH TRIMETHYLCHLOROSILANE IN THE PRESENCE OF ZINC.
-
Ultrasonic waves increase the rates and the yields of the reactions of some α-dicarbonyls towards zinc and trimethylchlorosilane to give bis(trimethylsiloxy)alkenes.
- Boudjouk, Philip,So, Jeung Ho
-
p. 775 - 778
(2007/10/02)
-
- SYNTHETIC APPLICATIONS OF CHROMIUM(VI) REAGENTS IN COMBINATION WITH CHLOROTRIMETHYLSILANE
-
The synthetic utility of chromium(VI) reagents together with chlorotrimethylsilane, as new oxidizing systems, is described.Pyridinium dichromate (PDC) in combination with chlorotrimethylsilane oxidizes tert-butyldimethylsilyl ethers in good to excellent yields.Trimethylsilyl chlorochromate, a new chromium(VI) reagent, also was found efficient for this oxidative-deprotection method.These reagents were applied to the oxidation of some N-(2-phenyl-2-hydroxyethyl)azetidin-2-ones as well as N-(2-phenyl-2-trialkylsiloxy)azetidin-2-ones into their corresponding carbonyl compounds, key intermediates for N-unsubstituted β-lactams.Oxidation of hydroquinones and protected trialkylsilyl hydroquinones was also described.Protection of hydroquinones by means of the tert-butyldimethylsilyl group was achieved by using the readily available tert-butyldimethylchlorosilane (TBDMCS) and 1,8-diazabicycloundec-7-ene (DBU) as base, which avoids the use of sophisticated and (or) sensitive reagents.
- Cossio, Fernando P.,Aizpurua, Jesus M.,Palomo, Claudio
-
p. 225 - 231
(2007/10/02)
-
- Cyclic Ions in the Mass Spectra of Trimethylsilyl Derivatives of Substituted o-Dihydroxybenzenes
-
The mass spectra of trimethylsilyl (TMS) ethers/methyl esters of phenolic acids containing o-dihydroxybenzene groups have base peaks at (1+) instead of the usual (1+) and (1+) that are characteristic of TMS/methyl esters of monohydroxyphenolic acids.These ions, formed by the loss of 31+88 u from the parent ion, possess a cyclic moiety as proven by substitution of deuterium atoms for hydrogen atoms in the TMS groups of the methyl esters of 3,4,5-trihydroxybenzoic (gallic), 3,4-dihydroxybenzoic (protocatechuic) and β-(3,4-dihydroxyphenyl)propenoic (caffeic) acids.Although these cyclic ions are the base peaks in TMS-derivatized o-dihydroxyphenolic acid esters, similar ions represent intense peaks but not neccessarily the base peak in other derivatized compounds such as 1,2-dihydroxybenzene, 1,2-dihydroxy-3-methyl- and 1,2-dihydroxy-4-methyl-benzenes and flavan-3-ols that possess o-dihydroxybenzene groups.Compounds possessing m- or p-dihydroxybenzene groups do not form these cyclic ions; therefore, this procedure for derivatization and interpretation of mass spectra is valuable for the identification of compounds containing o-dihydroxybenzene groups in complex mixtures of isomeric compounds.
- Horvat, Robert J.,Senter, Samuel D.
-
p. 413 - 417
(2007/10/02)
-
- TRIMETHYLSILYLATED N-ALKYL-SUBSTITUTED CARBAMATES. I. PREPARATION AND SOME REACTIONS
-
Trimethylsilyl N-monoalkyl- and N,N-dialkyl-carbamates have been made in 85-95percent yields by silylation of the corresponding ammonium carbamates with trimethylchlorosilane.Trimethylsilyl N,N-dimethylcarbamate can be used for silylation of alcohols, phenols, and carboxylic acids.The silylcarbamates react with carboxylic acid halides to give the corresponding acid amides.The reaction of trimethylsilyl carbamates with carboxylic anhydrides give the corresponding silyl carboxylate and acid amide, while the reaction with dicarboxylic anhydrides give the trimethylsilyl monoamide of the corresponding dicarboxylic acid, i.e.Me3SiO2CCONR1R2.
- Knausz, Dezsoe,Meszticzky, Aranka,Szakacs, Laszlo,Csakvari, Bela,Ujszaszy, Kalman
-
-
- Pyridinium Chlorochromate Releases Quinones from Hydroquinone Silyl Ethers.
-
The pyridinium chlorochromate oxidation of six bis(trimethylsilyl) and six bis(tert-butyldimethylsilyl) ethers of p-hydroquinones at room temperature in methylene chloride solution gave the corresponding quinones in 60-90percent yield.The bis(trimethylsilyl) ethers were slightly more reactive than the bis(tert-butyldimethylsilyl) ethers.High oxidation efficiency was indicated by a 1:1 molar stoichiometry; however, more convenient reaction times were obtained at a 2:1 molar ratio of pyridinium chlorochromate (PCC) to hydroquinone silyl ether.The mechanism is discussed based upon comparisons of relative reaction rates with electrochemical oxidation potentials.
- Willis, John P.,Gogins, Kitty A.,Miller, Larry L.
-
p. 3215 - 3218
(2007/10/02)
-
- Tetrasubstituted Tetrazenes (Me3E)2N-N=N-N(EMe3)2 (E = Si, Ge, Sn): Reactivity
-
By substitution of the silyl, germyl, or stannyl groups, (Me3Si)2N-N=N-N(SiMe3)2 (1) reacts with variable amounts of trifluoroacetic acid to form (Me3Si)4-nN4Hn, (Me3Ge)2N-N=N-N(GeMe)2 (2) with variable amounts of methanol to form (Me3Ge)4-nN4Hn, and (Me3Sn)2N-N=N-N(SnMe3)2 (3) with variable amounts of trimethylchlorosilane to give (Me3Sn)4-nN4(SiMe3)n (n = 1-4).The reaction of 1 with benzenesulfonyl isocyanate leads by substitution and cyclization to silylated 5-hydroxytetrazole 12.Substitution in connection with thermolysis of the substitution products formed is found in the reaction of 1 with methanol, aluminium chloride, or nitrosyl chloride and in the reaction of 3 with trimethylstannane, acetone, or nitrosobenzene.By oxidation of 1 with chlorine, bromine, or p-benzoquinone and of 3 with p-benzoquinone or oxygen, all tetrazene nitrogen is envolved.The reduction of 1 with hydrogen or alkali metals leads to nitrogen and (Me3Si)2NH or (Me3Si)2NM.
- Wiberg, Nils,Bayer, Heiner,Vasisht, Sham Kumar,Meyers, Rene
-
p. 2916 - 2927
(2007/10/02)
-
- Oxidation of Hydroquinone Silyl Esters to Quinones
-
The electrochemical oxidation of trialkylsiloxybenzene derivatives was investigated using platinum and graphite anodes in either acetonitrile or methylene chloride solvent.Preparative oxidation of the bis(trimethylsilyl) ethers of hydroquinone, chlorohydroquinone, 2,5-di-tert-butylhydroquinone, and 9,10-dihydroxyanthracene gave the corresponding quinones in 80-90percent yield.Oxidation of 1,4-bis(trimethylsiloxy)-2-methoxybenzene in acetonitrile gave 3,6-dihydroxy-2,7-dimethoxydibenzofuran in 65percent yield.Oxidation of 1-methoxy-4-(trimethylsiloxy)benzene in methanolic acetonitrile produced 1,1-dimethoxy-2,5-cyclohexadien-4-one in 99percent yield.The cyclic voltammograms of the trimethylsilyl, triethylsilyl, and tert-butyldimethylsilyl ethers of 2,5-di-tert-butylhydroquinone were recorded using acetonitrile and methylene chloride solvents at 25 and -60 deg C.These compounds were found to react by initial one-electron oxidation to generate a cation radical which decomposes by silicon-oxygen bond cleavage to eventually form quinone.The relative rates for decomposition of the trimethylsilyl, triethylsilyl, and tert-butyldimethylsilyl ether cation radicals at -60 deg C were 10:5:1. tert-Butyldimethylsilyl chloride and tert-butyldimethylsilyl triflate were found to be stable toward cathodic reduction in dry methylene chloride and acetonitrile at potentials as negative as -2.1 vs.Ag/0.1 M AgNO3.Cyclic voltammetry indicated that reduction of 2,5-di-tert-butylbenzoquinone, anthraquinone, and naphthoquinone in the presence of tert-butyldimethylsilyl chloride resulted in reductive silylation.
- Stewart, Ray F.,Miller, Larry L.
-
p. 4999 - 5004
(2007/10/02)
-