- Hydrosilane-Promoted Facile Deprotection of tert-Butyl Groups in Esters, Ethers, Carbonates, and Carbamates
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Combination of PdCl2 with 1,1,3,3-tetramethyldisiloxane in the presence of activated carbon was found to be an effective catalyst system for the cleavage reaction of C?O bond of O?t-Bu moieties. The present catalytic reaction offers a practical method for the deprotection of tert-butyl esters, tert-butyl ethers, O-Boc, and N-Boc derivatives under mild conditions. The addition of activated carbon in the reaction mixture was proved to be crucial for not only sustaining the catalytic activity but also trapping the palladium species after the reaction. (Figure presented.).
- Ikeda, Takuya,Zhang, Zhenzhong,Motoyama, Yukihiro
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p. 673 - 677
(2019/01/04)
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- Remarkably high catalyst efficiency of a disilaruthenacyclic complex for hydrosilane reduction of carbonyl compounds
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A disilaruthenacyclic complex (1) showed extremely high catalytic activity for hydrosilane reduction of aldehydes and ketones to silyl ethers and secondary and tertiary amides to the corresponding amines. An σ-CAM mechanism was proposed to explain the activity.
- Tahara, Atsushi,Sunada, Yusuke,Takeshita, Takashi,Inoue, Ryoko,Nagashima, Hideo
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supporting information
p. 11192 - 11195
(2018/10/24)
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- An efficient method for the reductive conversion of acyclic esters to ethers via a TMS-protected acetal
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We report an efficient two step process for the reduction of non-aromatic esters to the corresponding ethers via the intermediate TMS-protected acetal. The acetal formed after the first step can be carried on directly to the subsequent reduction to the ether without purification. The ester reduction step was monitored using in-situ ReactIR for disappearance of the C[dbnd]O peak, allowing for the exact determination of time and equivalents of the reducing agent. Furthermore, use of TMS-imidazole to form the acetal has allowed us to dramatically reduce the overall reaction time required for the two step procedure.
- Hart, Alison,Kelley, Sarah A.,Harless, Tyler,Hood, John A.,Tagert, Michael,Pigza, Julie A.
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supporting information
p. 3024 - 3027
(2017/07/17)
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- Development of a Triazine-Based tert-Butylating Reagent, TriAT-tBu
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A new tert-butylating reagent, 2,4,6-tris(tert-butoxy)-1,3,5-triazine (TriAT-tBu) has been developed for the acid-catalyzed tert-butylation of alcohols and carboxylic acids. The reaction of various alcohols and carboxylic acids with TriAT-tBu in the presence of a catalytic amount of an acid provided the corresponding tert-butyl ethers and esters in good to high yields. TriAT-tBu is an air-stable solid synthesized in good yield from inexpensive starting materials, namely, cyanuric chloride, tBuOH, and sodium hydride.
- Yamada, Kohei,Hayakawa, Naoko,Fujita, Hikaru,Kitamura, Masanori,Kunishima, Munetaka
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p. 4093 - 4098
(2016/08/24)
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- HYDROXY GROUP PROTECTING AGENT AND HYDROXY GROUP PROTECTION METHOD
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To provide: a hydroxy group protecting agent which is stable and easy to use, does not have carcinogenicity, a tearing property or the like, and is inexpensive; and a hydroxy group protection method which enables the protection of a hydroxy group under acidic conditions. [Solution] A hydroxy group protecting agent in which at least one protecting group is bound to a nitrogen-containing electron-withdrawing heterocyclic ring through any one of an oxygen atom, a sulfur atom and a nitrogen atom. The heterocyclic ring is a triazine ring or the like, and the protecting group is a benzyl group or the like. Specifically, the hydroxy group protecting agent is 2,4,6-tribenzyloxy-1,3,5-triazine, 2,4,6-tris(4-methoxybenzyloxy)-1,3,5-triazine or the like. In addition, 2,4,6-tris(t-butoxy)-1,3,5-triazine or the like can also be used. For protecting a hydroxy group, a compound of interest which has a hydroxy group is reacted with the hydroxy group protecting agent under acidic conditions.
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Paragraph 0059; 0060; 0061
(2015/01/07)
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- The efficiency of the metal catalysts in the nucleophilic substitution of alcohols is dependent on the nucleophile and not on the electrophile
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In this study, we investigate the effect of the electrophiles and the nucleophiles for eight catalysts in the catalytic SN1 type substitution of alcohols with different degree of activation by sulfur-, carbon-, oxygen-, and nitrogen-centered nucleophiles. The catalysts do not show any general variance in efficiency or selectivity with respect to the alcohols and follow the trend of alcohol reactivity. However, when it comes to the nucleophile, the eight catalysts show general and specific variances in the efficiency and selectivity to perform the desired substitution. Interestingly, the selectivity of the alcohols to produce the desired substitution products was found to be independent of the electrophilicity of the generated carbocations but highly dependent on the ease of formation of the cation. Catalysts based on iron(III), bismuth(III), and gold(III) show higher conversions for S-, C-, and N-centered nucleophiles, and BiIII was the most efficient catalyst in all combinations. Catalysts based on rhenium(I) or rhenium(VII), palladium(II), and lanthanum(III) were the most efficient in performing the nucleophilic substitution on the various alcohols with the O-centered nucleophiles. These catalysts generate the symmetrical ether as a by-product from the reactions of S-, C-, and N-centered nucleophiles as well, resulting in lower chemoselectivity. Who's the boss? In a comprehensive study of catalytic S N1 type direct substitution of alcohols, the catalysts do not show any general variance in efficiency or selectivity with respect to the alcohols but are highly variable with respect to the nucleophiles. The reactivity of the alcohols is independent of the electrophilicity of the generated carbocations but highly dependent on the ease of formation of the cation.
- Biswas, Srijit,Samec, Joseph S. M.
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supporting information
p. 974 - 981
(2013/08/25)
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- Direct synthesis of unsymmetrical ethers from alcohols catalyzed by titanium cation-exchanged montmorillonite
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Titanium-exchanged montmorillonite (Ti4+-mont) was found to act as an efficient heterogeneous catalyst for the etherification of a wide range of alcohols under mild reaction conditions. Ti4+-mont was reusable with retention of high efficiency and applicable to scale-up reaction conditions. The Royal Society of Chemistry 2012.
- Mitsudome, Takato,Matsuno, Tsuyoshi,Sueoka, Shoichiro,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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supporting information; experimental part
p. 610 - 613
(2012/04/23)
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- TiCl4-activated selective nucleophilic substitutions of tert-butyl alcohol and benzyl alcohols with π-donating substituents
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TiCl4-activated selective nucleophilic substitution reactions of tert-butyl alcohol and benzyl alcohols with π-donating substituents in the presence of primary and secondary alcohols can be carried out with various oxygen, nitrogen and carbon nucleophiles in good yields.
- Tsai, Chen-Yu,Sung, Robert,Zhuang, Bo-Ren,Sung, Kuangsen
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experimental part
p. 6869 - 6872
(2010/09/18)
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- Water compatible gold(III)-catalysed synthesis of unsymmetrical ethers from alcohols
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An efficient and broad-scoped method for the preparation of unsymmetrical ethers from alcohols catalysed by the simplest and least expensive gold catalyst, NaAuCl4, is described for the first time. The procedure enables the etherification of benzylic and tertiary alcohols with moderate to good yields under mild conditions with low catalyst loading. Symmetrical ethers, the usual side products in the etherification of alcohols, were not detected in this case. The formation of the racemic ether from a chiral benzyl alcohol suggests the intermediacy of a carbocation, which has not previously been postulated for gold-catalysed reactions involving alcohols.
- Cuenca, Ana B.,Mancha, Gisela,Asensio, Gregorio,Medio-Simon, Mercedes
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experimental part
p. 1518 - 1523
(2009/04/04)
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- A highly efficient method for the reductive etherification of carbonyl compounds with triethylsilane and alkoxytrimethylsilane catalyzed by iron(III) chloride
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Facile reductive etherification of carbonyl compounds can be conveniently performed by reaction with triethylsilane and alkoxytrimethylsilane catalyzed by iron(III) chloride. The corresponding alkyl ethers, including benzyl and allyl ethers, of the reduced alcohols were obtained in good to excellent yields under mild reaction conditions.
- Iwanami, Katsuyuki,Seo, Hana,Tobita, Yuki,Oriyama, Takeshi
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p. 183 - 186
(2007/10/03)
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- A triruthenium carbonyl cluster bearing a bridging acenaphthylene ligand: An efficient catalyst for reduction of esters, carboxylic acids, and amides by trialkylsilanes
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An efficient reduction of carboxylic acids, esters, and amides with trialkylsilanes is accomplished using a triruthenium carbonyl cluster bearing a bridging acenaphthylene ligand, (μ3,η2:η3:η5 -acenaphthylene)Ru3(CO)7, as the catalyst. Preactivation of the catalyst by hydrosilanes accelerates the reactions. Sterically small trialkylsilanes are effective in these reactions. Reduction of carboxylic acids and amides efficiently produces the corresponding silyl ethers and amines, respectively. Reduction of esters gives a mixture of silyl and alkyl ethers, but can be controlled by changing the silanes and solvents.
- Matsubara, Kouki,Iura, Takafumi,Maki, Tomoyuki,Nagashima, Hideo
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p. 4985 - 4988
(2007/10/03)
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- Improved procedure for the reductive acetylation of acyclic esters and a new synthesis of ethers
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An optimized protocol for the DIBALH reductive acetylation of acyclic esters and diesters is described. This reductive acetylation procedure allows a wide variety of esters to be converted into the corresponding α-acetoxy ethers in good to excellent yields. It was found that, under mild acidic conditions, many α-acetoxy ethers can be further reduced to the corresponding ethers. This net two-step ester deoxygenation is an attractive alternative to the classical Williamson synthesis for certain ethers.
- Kopecky, David J.,Rychnovsky, Scott D.
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p. 191 - 198
(2007/10/03)
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- Convenient preparations of t-butyl esters and ethers from t-butanol
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A one-pot preparation of t-butyl esters and ethers is described that proceeds from the carboxylic acid or alcohol and t-butanol using only anhydrous magnesium sulfate and catalytic sulfuric acid as additional reagents. The method affords t-butyl esters and ethers in good yields and is applicable to a variety of substrates.
- Wright, Stephen W.,Hageman, David L.,Wright, Ann S.,McClure, Lester D.
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p. 7345 - 7348
(2007/10/03)
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- PHOTOINDUCED OXIDATIVE CLEAVAGE OF ARYLCYCLOPROPANES IN THE PRESENCE OF ORGANIC ELECTRON-ACCEPTOR
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The cyclopropane ring of arylcyclopropanes is oxidatively cleaved by irradiation in polar solvents containing nucleophiles such as alcohols, water, and sodium cyanide in the presence of electron-acceptor such as 1,4-dicyanobenzene and 1-cyanonaphthalene, giving nucleophile-incorporated products.This photoreaction proceeds via an electron-transfer from the cyclopropanes to the excited electron-acceptors, and the cation radicals of arylcyclopropanes are involved as key intermediates.
- Mizuno, Kazuhiko,Ogawa, Jun,Otsuji, Yoshio
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p. 741 - 744
(2007/10/02)
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