- A Noncoordinating Acid-Base Catalyst for the Mild and Nonreversible tert-Butylation of Alcohols and Phenols
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A mild and nonreversible tert-butylation of alcohols and phenols can be achieved in high yields using the noncoordinating acid-base catalyst [bis(trifluoromethane)sulfonimide and 2,6-lutidine] with a tert-butylation reagent, tert-butyl 2,2,2-trichloroacetimidate. This method allows the use of substrates containing acid sensitive groups such as ketal, Boc, and boronate esters.
- Fandrick, Keith R.,Patel, Nitinchandra D.,Radomkit, Suttipol,Chatterjee, Arindom,Braith, Stefan,Fandrick, Daniel R.,Busacca, Carl A.,Senanayake, Chris H.
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- Zn- And Cu-catalyzed coupling of tertiary alkyl bromides and oxalates to forge challenging C?O, C?S, and C?N bonds
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We describe here the facile construction of sterically hindered tertiary alkyl ethers and thioethers via the Zn(OTf)2catalyzed coupling of alcohols/phenols with unactivated tertiary alkyl bromides and the Cu(OTf)2-catalyzed thiolation of unactivated tertiary alkyl oxalates with thiols. The present protocol represents one of the most effective unactivated tertiary C(sp3)? heteroatom bond-forming conditions via readily accessible Lewis acid catalysis that is surprisingly less developed.
- Gong, Yuxin,Zhu, Zhaodong,Qian, Qun,Tong, Weiqi,Gong, Hegui
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supporting information
p. 1005 - 1010
(2021/02/01)
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- A study of diketopiperazines as electron-donor initiators in transition metal-free haloarene-arene coupling
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Several diketopiperazines have been shown to promote carbon-carbon coupling between benzene and aryl halides in the presence of potassium tert-butoxide and without the assistance of a transition metal catalyst. The structure of the diketopiperazine has an influence on its reductive potential and can help to promote the coupling of the more challenging aryl bromides with benzene.
- Cumine, Florimond,Zhou, Shengze,Tuttle, Tell,Murphy, John A.
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p. 3324 - 3336
(2017/04/21)
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- Iron-mediated direct arylation of unactivated arenes in air
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Biaryls are a common motif in both natural and synthetic chemicals. Several methods have recently been reported for the preparation of these compounds using direct arylation catalyzed by iron, other base metals, or transition-metal-free systems. To date, these methods have all required inert and/or forcing conditions, which limited their application in routine organic synthesis. In this article we report a protocol for direct arylation using a convenient FeCl3/1,10-phenanthroline system as precatalyst. The reaction proceeds under mild conditions (100 °C), under air, and with non-distilled solvent. A simple, environmentally benign catalytic system based on iron trichloride and phenanthroline has been developed for the direct arylation of unactivated arenes with aryl halides under air. Copyright
- Huang, Yuxing,Moret, Marc-Etienne,Klein Gebbink, Robertus J. M.
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supporting information
p. 3788 - 3793
(2014/06/24)
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- An eco-sustainable erbium(III) triflate catalyzed formation and cleavage of tert -butyl ethers
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An eco-compatible method, which permits the formation or cleavage of tert-butyl ethers of alcohols and phenols, is proposed. The protection step is performed in solvent-free conditions at room temperature using catalytic amount of Er(OTf)3. The catalyst is easily- recovered from the aqueous phase and reused several times without significant loss of activity. The deprotection step developed is also highly eco-friendly since the tert-butyl group is removed very quickly from alcohols and phenols in methanol using MW irradiation-. Georg Thieme Verlag Stuttgart · New York.
- Procopio, Antonio,Costanzo, Paola,Curini, Massimo,Nardi, Monica,Oliverio, Manuela,Paonessa, Rosina
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supporting information; experimental part
p. 73 - 78
(2011/03/19)
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- An eco-sustainable erbium(iii)-catalyzed method for formation/cleavage of O-tert-butoxy carbonates
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A new simple and effective method for the formation/cleavage of O-tert-butoxy carbonates of alcohols and phenols is proposed. Mesoporous silica-supported Er(iii) (ErIII-MCM-41) was used as an efficient and reusable solid catalyst in the solvent-free ultrasound-assisted synthesis of Boc-carbonate derivatives of a wide range of alcohols and phenols. The fast, selective deprotection of Boc-derivatives is achieved with a very low amount of Er(OTf)3 in ethanol under microwave irradiation. Therefore, the entire protection/de-protection process is very attractive, from the point of view of sustainability.
- Procopio, Antonio,Cravotto, Giancarlo,Oliverio, Manuela,Costanzo, Paola,Nardi, Monica,Paonessa, Rosina
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p. 436 - 443
(2011/04/17)
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- A convenient synthesis of tert-butyl ethers under microwave condition
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Synthesis of tert-butyl ethers from various alcohols and substituted phenols can be achieved using tert-butyl bromide in the presence of basic lead carbonate as a catalyst under microwave irradiation in absence of solvent. The catalyst is easily recovered via filtration and reused up to three times without appreciable loss of activity.
- Mahammed,Keshava Murthy,Mohana Raju
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p. 575 - 578
(2008/09/20)
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- Efficient synthesis of tert-butyl ethers under solvent-free conditions
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A simple and efficient synthesis of tert-butyl ethers from various alcohols and substituted phenols using tert-butyl bromide in the presence of basic lead carbonate as a catalyst. The catalyst is easily recovered via filtration and can be reused up to three times without appreciable loss of activity. Copyright Taylor & Francis Group, LLC.
- Rai, Neithnadka Premsai,Arunachalam, Pirama Nayagam
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p. 2891 - 2896
(2008/02/13)
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- Alcohols and di-tert-butyl dicarbonate: How the nature of the Lewis acid catalyst may address the reaction to the synthesis of tert-butyl ethers
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The reaction between alcohols and Boc2O leads to the formation of ferf-butyl ethers and/or Boc-alcohols, depending on the nature of the Lewis acid catalyst. Product distribution is mainly tuned by the anionic part of the salt. Perchlorates and Inflates, anions with highly delocalized negative charge, give prevalent or exclusive ether formation. On the other hand, Boc alcohols are the main or exclusive products with un-delocalized isopropoxide or low-delocalized acetate ions. The metal ion influences only the reaction rate, roughly following standard parameters for calculating Lewis acidity. A reaction mechanism is supposed, and a series of experimental evidences is reported to support it. These studies allowed us to conclude that, to synthesize tert-butyl ethers, in reactions involving aliphatic alcohols, Mg(ClO4) 2 or Al(ClO4)3 represents the best compromise between costs and efficiency of the reaction, while, in reactions involving phenols, Sc(OTf)3 is the best choice, since aromatic tert-butyl ethers are not stable in the presence of perchlorates.
- Bartoli, Giuseppe,Bosco, Marcella,Carlone, Armando,Dalpozzo, Renato,Locatelli, Manuela,Melchiorre, Paolo,Sambri, Letizia
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p. 9580 - 9588
(2007/10/03)
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- Unusual and unexpected reactivity of t-butyl dicarbonate (Boc2O) with alcohols in the presence of magnesium perchlorate. A new and general route to t-butyl ethers
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(Chemical Equation Presented) A new mild method for protecting alcohols as t-butyl ethers is reported. The reaction proceeds with Mg(ClO4) 2 and Boc2O and shows general applicability. The deprotection of t-butyl ethers has also been revisited. Preliminary results indicate the CeCl3·7H2O/Nal system is a very suitable catalyst for their removal.
- Bartoli, Giuseppe,Bosco, Marcella,Locatelli, Manuela,Marcantoni, Enrico,Melchiorre, Paolo,Sambri, Letizia
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p. 427 - 430
(2007/10/03)
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- Catalyst for aromatic C—O, C—N, and C—C bond formation
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The present invention is directed to a transition metal catalyst, comprising a Group 8 metal and a ligand having the structure wherein R, R′ and R″ are organic groups having 1-15 carbon atoms, n=1-5, and m=0-4. The present invention is also directed to a method of forming a compound having an aromatic or vinylic carbon-oxygen, carbon-nitrogen, or carbon-carbon bond using the above catalyst. The catalyst and the method of using the catalyst are advantageous in preparation of compounds under mild conditions of approximately room temperature and pressure.
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- Air stable, sterically hindered ferrocenyl dialkylphosphines for palladium-catalyzed C-C, C-N, and C-O bond-forming cross-couplings
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Pentaphenylferrocenyl di-tert-butylphosphine has been prepared in high yield from a two-step synthetic procedure, and the scope of various cross-coupling processes catalyzed by complexes bearing this ligand has been investigated. This ligand creates a remarkably general palladium catalyst for aryl halide amination and for Suzuki coupling. Turnovers of roughly 1000 were observed for aminations with unactivated aryl bromides or chlorides. In addition, complexes of this ligand catalyzed the formation of selected aryl ethers under mild conditions. The reactions encompassed electron-rich and electron-poor aryl bromides and chlorides. In the presence of catalysts containing this ligand, these aryl halides coupled with acyclic or cyclic secondary alkyl- and arylamines, with primary alkyl- and arylamines, and with aryl- and primary alkylboronic acids. These last couplings provide the first general procedure for reaction of terminal alkylboronic acids with aryl halides without toxic or expensive bases. The ligand not only generates highly active palladium catalysts, but it is air stable in solution and in the solid state. Palladium(0) complexes of this ligand are also air stable as a solid and react only slowly with oxygen in solution.
- Kataoka, Noriyasu,Shelby, Quinetta,Stambuli, James P.,Hartwig, John F.
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p. 5553 - 5566
(2007/10/03)
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- Palladium/P(t-Bu)3-catalyzed synthesis of aryl t-butyl ethers and application to the first synthesis of 4-chlorobenzofuran
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Pd/P(t-Bu)3 catalyzed reaction of aryl halides with sodium t-butoxide effectively to give aryl t-butyl ethers. The high catalytic activity realized the formation of aryl t-butyl ethers from not only electron-deficient aryl halides but also electron-rich aryl halides. Moreover, the first synthesis of 4-chlorobenzofuran was attained utilizing the selective mono-t-butoxylation of aryl dihalide.
- Watanabe, Makoto,Nishiyama, Masakazu,Koie, Yasuyuki
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p. 8837 - 8840
(2007/10/03)
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- Norrish Type I Photoreaction in the Presence of Phenols; an Intermolecular Photo-Fries Rearrangement
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Pinacolone photolysis in the presence of phenols leads to phenyl acetates and hydroxy acetophenones; Norrish type I cleavage and subsequent hydrogen abstraction from the phenol by the tert-butyl radical gives rise to acyl-aryloxy radical pairs which recombined constituting an intermolecular photo-Fries rearrangement.
- Jimenez, M. Consuelo,Leal, Pablo,Miranda, Miguel A.,Tormos, Rosa
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p. 2009 - 2010
(2007/10/02)
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- Arylation with 1,3-Dinitroarenes and Copper(I) t-Butoxide. Scope and Limitations
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The reaction of 1,3-dinitrobenzene with copper(I) t-butoxide and an iodoarene, which produces a 2,6-dinitrobiphenyl, has been stidied in detail with a variety of substrates.Iodoarenes containing ester, aldehyde, or other halogen functions were effective, but replacement of the iodoarene with a bromoarene, iodoalkyne, or iodoalkene resulted in less efficient coupling, promoting side-reactions.On replacing the second nitro group on the dinitrobenezene with nitrile, ester, amide, or trifluoromethyl groups, little or no coupling was observed.Limiting side-reactions usually involved the decomposition of substrates by t-butoxide via nucleophilic substitution, elimination, or deprotonation.A mechanism based on reversible cupration of the dinitroarene is proposed.
- Carter, Stephen D.,Wallace, Timothy W.
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p. 1601 - 1633
(2007/10/02)
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- Preparation of 2-t-butyl-4-alkoxy- and 4-hydroxyphenols
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Tertiary alkyl phenyl ethers may be induced to undergo thermal rearrangement on an alumina catalyst to afford the isomeric ortho-t-alkylphenol. Such rearrangement generally occurs under milder conditions than does the alkylation of a phenol with an olefin using the same alumina as an alkylating catalyst. The rearrangement remains regioselective even when the phenyl ring bears an alkoxy group, hence affords a good preparative route to such materials as 2-t-butyl-4-methoxyphenol.
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