- Efficient and selective protection of alcohols and phenols with triisopropylsilyl chloride/imidazole using microwave irradiation
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A very simple and efficient method is described for silylation of alcohols and phenols using triisopropylsilyl chloride and imidazole under microwave irradiation. High selectivity was observed for silylation of primary and secondary alcohols and also for structurally different phenols. (C) 2000 Published by Elsevier Science Ltd.
- Khalafi-Nezhad, Ali,Fareghi Alamdari, Reza,Zekri, Negar
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- Spatial anion control on palladium for mild C-H arylation of arenes
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C-H arylation of arenes without the use of directing groups is a challenge, even for simple molecules, such as benzene. We describe spatial anion control as a concept for the design of catalytic sites for C-H bond activation, thereby enabling nondirected C-H arylation of arenes at ambient temperature. The mild conditions enable late-stage structural diversification of biologically relevant small molecules, and site-selectivity complementary to that obtained with other methods of arene functionalization can be achieved. These results reveal the potential of spatial anion control in transition-metal catalysis for the functionalization of C-H bonds under mild conditions.
- Dhankhar, Jyoti,González-Fernández, Elisa,Dong, Chao-Chen,Mukhopadhyay, Tufan K.,Linden, Anthony,?ori?, Ilija
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supporting information
p. 19040 - 19046
(2020/11/13)
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- Ligand-Promoted Non-Directed C?H Cyanation of Arenes
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This article reports the first example of a 2-pyridone accelerated non-directed C?H cyanation with an arene as the limiting reagent. This protocol is compatible with a broad scope of arenes, including advanced intermediates, drug molecules, and natural products. A kinetic isotope experiment (kH/kD=4.40) indicates that the C?H bond cleavage is the rate-limiting step. Also, the reaction is readily scalable, further showcasing the synthetic utility of this method.
- Liu, Luo-Yan,Yeung, Kap-Sun,Yu, Jin-Quan
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supporting information
p. 2199 - 2202
(2019/01/24)
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- Mild synthesis of silyl ethers: Via potassium carbonate catalyzed reactions between alcohols and hydrosilanes
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A method has been developed for the silanolysis of alcohols using an abundant and non-corrosive base K2CO3 as a catalyst. Reactions between a variety of alcohols and hydrosilanes generate silyl ethers under mild conditions. The use of hydrosilanes leads to the formation of H2 as the only byproduct thus avoiding the formation of stoichiometric strong acids. The mild conditions lead to a wide scope of possible alcohol substrates and good functional group tolerance. Selective alcohol silanolysis is also observed in the presence of reactive C-H bonds, lending this method for extensive use in protection group chemistry.
- Delucia, Nicholas A.,Das, Nivedita,Vannucci, Aaron K.
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p. 3415 - 3418
(2018/05/23)
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- Direct C-H Cyanation of Arenes via Organic Photoredox Catalysis
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Methods for the direct C-H functionalization of aromatic compounds are in demand for a variety of applications, including the synthesis of agrochemicals, pharmaceuticals, and materials. Herein, we disclose the construction of aromatic nitriles via direct C-H functionalization using an acridinium photoredox catalyst and trimethylsilyl cyanide under an aerobic atmosphere. The reaction proceeds at room temperature under mild conditions and has proven to be compatible with a variety of electron-donating and -withdrawing groups, halogens, and nitrogen- and oxygen-containing heterocycles, as well as aromatic-containing pharmaceutical agents.
- McManus, Joshua B.,Nicewicz, David A.
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supporting information
p. 2880 - 2883
(2017/03/11)
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- An efficient synthesis of silyl ethers of primary alcohols, secondary alcohols, phenols and oximes with a hydrosilane using InBr3 as a catalyst
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An efficient method for the preparation of silyl ethers by InBr3 catalyzed silylation of primary alcohols, secondary alcohols, phenols and oxime with a hydrosilane is described.
- Sridhar, Madabhushi,Raveendra, Jillella,China Ramanaiah, Beeram,Narsaiah, Chinthala
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experimental part
p. 5980 - 5982
(2011/12/02)
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- CATALYTIC DISPROPORTIONATION AND CATALYTIC REDUCTION OF CARBON-CARBON AND CARBON-OXYGEN BONDS OF LIGNIN AND OTHER ORGANIC SUBSTRATES
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The present invention provides methods and catalyst compositions for the catalytic reduction of carbon-oxygen bonds of organic substrates and the catalytic disproportionation of carbon-oxygen or carbon-carbon bonds of organic substrates. These methods and catalyst compositions may be used to depolymerize lignin. The disproportionation of carbon-oxygen or carbon-carbon bonds of organic substrates or lignin is carried out by cleaving a carbon-oxygen bond or a carbon-carbon bond in a catalytic disproportionation reaction. The catalysts may be formed from a metal precursor such as ruthenium or vanadium and a bidentate ligand The catalytic reduction of carbon-oxygen bonds of organic substrates such as lignin is carried out by cleaving a carbon-oxygen bond in the presence of a hydrogen atom source. Lignin fragments produced following depolymerization by such methods may be further processed into fuels.
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- Effective silylation of carboxylic acids under solvent-free conditions with tert-butyldimethylsilyl chloride (TBDMSCL) and triisopropylsilyl chloride (TIPSCL)
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Varions types of carboxylic acids can be converted effectively to their corresponding TBDMS and TIPS esters using TBDMSCI and TIPSCI in the presence of imidazole under solvent-free conditions. The advantage of this modified method in comparison with that reported by Corey is the elimination of DMF, which eliminates aqueous work-up. The method is not a time-consuming process and the reactions proceed spontaneously. By this method, absolute chemoselectivity for the protection of carboxylic acid functions in the presence of 2°, 3° hydroxyl groups are observed.
- Firouzabadi, Habib,Iranpoor, Naser,Shaterian, Hamid Reza
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- Kinetics and Thermodynamics of Phenolate Silylation and Alkylation
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A kinetic and thermodynamic investigation of the silylation reactions of alkali phenolates with several trisubstituted silyl chlorides was performed in tetrahydrofuran, acetonitrile, and dimethyl sulfoxide.Heats and rates of reaction were determined by titration calorimetry and stopped-flow techniques and found to be strongly dependent upon solvent polarity, ion pairing of the alkali phenolate, and steric and electronic influences.Reaction rates were considerably faster in acetonitrile and dimethyl sulfoxide than in tetrahydrofuran where ion-pairing effects were significant.Rates were accelerated by the addition of crown ethers.In most cases, potassium phenolates were more reactive than the corresponding sodium phenolates.The order of reactivity observed for the silyl chlorides increased as follows: i-Pr3 a's of the parent phenols, and the appropriate Hammett ? constants.Hammett plots for the silylation reactions of substituted potassium phenolates with triphenylsilyl fluoride gave values of ρ = 1.24 and 2.40 for the reaction in acetonitrile and dimethyl sulfoxide, respectively.
- Ellington, Joe Carey,Arnett, E. M.
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p. 7778 - 7785
(2007/10/02)
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