- Enolate-Based Regioselective Anti-Beckmann C-C Bond Cleavage of Ketones
-
The Baeyer-Villiger or Beckmann rearrangements are established methods for the cleavage of ketone derivatives under acidic conditions, proceeding for unsymmetrical precursors selectively at the more substituted site. However, the fragmentation regioselectivity cannot be switched and fragmentation at the less-substituted terminus is so far not possible. We report here that the reaction of ketone enolates with commercial alkyl nitrites provides a direct and regioselective way of fragmenting ketones into esters and oximes or ω-hydroxyimino esters, respectively. A comprehensive study of the scope of this reaction with respect to ketone classes and alkyl nitrites is presented. Control over the site of cleavage is gained through regioselective enolate formation by various bases. Oxidation of kinetic enolates of unsymmetrical ketones leads to the otherwise unavailable "anti-Beckmann"cleavage at the less-substituted side chain, while cleavage of thermodynamic enolates of the same ketones represents an alternative to the Baeyer-Villiger oxidation or the Beckmann rearrangement under basic conditions. The method is suited for the transformation of natural products and enables access to orthogonally reactive dicarbonyl compounds.
- Jahn, Ullrich,Ma?ek, Tomá?
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p. 11608 - 11632
(2021/09/02)
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- Silver/manganese dioxide nanorod catalyzed hydrogen-borrowing reactions and tert-butyl ester synthesis
-
Silver/manganese dioxide (Ag@MnO2) nanorods are synthesized and characterized by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray powder diffraction, and X-ray photoelectron spectroscopy. It was discovered that Ag@MnO2 nanorods can realize hydrogen-borrowing reactions in high yields and are also effective for the synthesis of tert-butyl esters from aryl cyanides and tert-butyl hydroperoxide in a short period of time. Mechanistic experiments revealed that this catalytic system acts as a Lewis acid in hydrogen-borrowing reactions, while the synthesis of tert-butyl esters occurs through a radical pathway. This is the first report on the excellent catalytic activity of Ag@MnO2 nanorods as a catalyst.
- Luo, Huanhuan,Yang, Yike,Yang, Bobin,Xu, Zhaojun,Wang, Dawei
-
p. 708 - 715
(2021/03/03)
-
- Quinolin-8-yl Formate: A New Option for Small-Scale Carbonylation Reactions in Microwave Reactors
-
A convenient procedure for conducting small-scale carbonylations of aryl or benzyl halides in a microwave reactor by using quinolin-8-yl formate is described. The resulting 8-acyloxyquinolines were shown to be more reactive than phenyl esters in acyl-tran
- Maddocks, Christopher J.,Aathimanikandan, Sivakumar V.,Richardson, Jeffery,Ruble, J. Craig
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p. 1608 - 1612
(2020/09/09)
-
- Nickel-Catalyzed Esterification of Amides Under Mild Conditions
-
Abstract: The use of ligands to adjust the catalytic activity of the catalyst for esterification of amides is challenge in organic chemistry. In this paper, Nickel(II)-NHC-catalyzed the esterification reaction between N,N-di-Boc amide and alcohols at room temperature have been demonstrated. The imidazolium salt bearing a hydroxyl functionalized side arm showed high effective catalytic activity in the activation of the amide N–C bond in air atmosphere. Graphic Abstract: [Figure not available: see fulltext.].
- Li, Jun-Fei,Wang, Yao-Fang,Wu, Yuan-Yuan,Liu, Wen-Jing,Wang, Jun-Wen
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p. 874 - 880
(2019/11/13)
-
- A Zirconium Indazole Carboxylate Coordination Polymer as an Efficient Catalyst for Dehydrogenation-Cyclization and Oxidative Coupling Reactions
-
Rational ligand design is crucial for achieving widespread applications of coordination polymers. The preparation, structural characterisation, and catalytic applications of zirconium (IV) coordination polymer (Zr-IDA), which was derived from 1-(carboxymethyl)-1H-indazole-5-carboxylic acid are reported. The Zr-IDA catalyst contains porous and highly crystalline particles with a quasi-spherical morphology around 100 nm in size, and Zr was coordinated with both O and N as shown by FT-IR and XPS measurements. Importantly, the Zr-IDA catalyst shows great activity, selectivity and stability in the oxidative coupling of benzyl cyanides with tert-butyl hydroperoxide to afford tert-butyl peresters, and the dehydrogenation cyclization of o-phenylenediamines with aromatic alcohols to afford 1,2-disubstituted benzimidazole derivatives. Mechanistic investigations were carried out to study these reactions and the developed catalytic system in more detail.
- Sang, Xinxin,Hu, Xinyu,Tao, Rong,Zhang, Yilin,Zhu, Haiyan,Wang, Dawei
-
p. 123 - 129
(2020/02/21)
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- A Cyanide-Free Synthesis of Acylcyanides through Ru-Catalyzed C(sp3)-H-Oxidation of Benzylic Nitriles
-
A practical method for generation of acylcyanides devoid of any external cyanide sources is presented that relies on a mild Ru-catalyzed selective C?H-oxidation of benzylic nitriles. The starting materials are smoothly generated through condensation of the corresponding carboxylic acid amides using silanes. The obtained acylcyanides can be employed in a plethora of transformation as exemplified to some larger extend in the sequence of C?H-oxidation-Tischenko-rearrangement for the generation of structurally diverse benzoyloxycyanohydrines.
- Eisele, Pascal,Bauder, Michael,Hsu, Shih-Fan,Plietker, Bernd
-
p. 689 - 691
(2019/05/07)
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- Efficient synthesis of esters through oxone-catalyzed dehydrogenation of carboxylic acids and alcohols
-
Since esters are important organic synthesis intermediates, an environmentally friendly oxone catalyzed-esterification of carboxylic acids with alcohols has been developed. A series of carboxylic acid esters are obtained in high yield. This strategy requires mild reaction conditions, providing an attractive alternative for the construction of valuable carbonyl esters. Electron-rich and electron-deficient groups are compatible with the standard conditions and a variety of substrates are demonstrated. Moreover, the reaction could easily be adapted to typical prodrugs, drugs and gram-scale synthesis.
- Hou, Fei,Wang, Xi-Cun,Quan, Zheng-Jun
-
supporting information
p. 9472 - 9476
(2019/01/03)
-
- Chemoselective and Metal-Free Synthesis of Aryl Esters from the Corresponding Benzylic Alcohols in Aqueous Medium Using TBHP/TBAI as an Efficient Catalytic System
-
A novel and transition-metal-free strategy has been developed for the synthesis of aryl esters starting from corresponding benzylic primary alcohols as the exclusive substrates using tert -butyl hydroperoxide (TBHP) as a terminal oxidant in the presence of catalytic amount of tetrabutylammonium iodide (TBAI) and imidazole, where the aliphatic alcohols remained unaffected. These reactions are highly chemoselective and associated with high yield and wide applicability accommodating a wide range of substituents. Excellent chemoselectivity has also been demonstrated through intramolecular competition experiments. This protocol can be considered as an important analogue of Tishchenko reaction using benzylic alcohols as the substrates instead of benzaldehydes.
- Nandy, Sneha,Ghatak, Avishek,Das, Asit Kumar,Bhar, Sanjay
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p. 2208 - 2212
(2018/10/02)
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- A fast and practical synthesis of tert-butyl esters from 2-tert-butoxypyridine using boron trifluoride·diethyl etherate under mild conditions
-
A practical direct preparation of tert-butyl esters from 2-tert-butoxypyridine has been developed. This system features the use of boron trifluoride·diethyl etherate in toluene solvent to rapidly achieve the reaction at room temperature. Using this reaction protocol, a variety of tert-butyl esters were synthesized from several different carboxylic acids at high yields. This practical procedure provides a promising and effective approach to the protection of carboxylic acids with a tert-butyl group.
- La, Minh Thanh,Kim, Hee-Kwon
-
p. 3748 - 3754
(2018/05/28)
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- Metal-free radical aromatic carbonylations mediated by weak bases
-
We report a new method of metal-free alkoxycarbonylation. This reaction involves the generation of aryl radicals from arenediazonium salts by a very weak base (HCO2Na) under mild conditions. Subsequent radical trapping with carbon monoxide and alcohols gives alkyl benzoates. The conditions (metal-free, 1 equiv. base, MeCN, r.t., 3 h) tolerate various functional groups (I, Br, Cl, CF3, SF5, NO2, ester). Mechanistic studies indicate the operation of a radical aromatic substitution mechanism.
- Koziakov, Denis,Jacobi Von Wangelin, Axel
-
supporting information
p. 6715 - 6719
(2017/08/22)
-
- A larene/ fragrant mixedsurrounds uncle butanol method for preparing ester compounds
-
The invention discloses a preparation method of an aromatic ring/aromatic heterocycle tert-butyl alcohol ester compound. The preparation method of the aromatic ring/aromatic heterocycle tert-butyl alcohol ester compound comprises the following steps of: firstly, under stirring condition, adding aromatic heterocycle borate compound or aromatic ring boric acid compound and di-tert-butyl dicarbonate ester into a solvent, and then adding a palladium catalyst and a ligand, so that a mixture A is obtained; secondly, heating the mixture A for carrying out reaction, and then cooling to room temperature, so that a mixture B is obtained; thirdly, diluting the mixture B with ethyl acetate, then filtering the diluted mixture B with diatomite, collecting filtrate, concentrating, and carrying out spin drying, so that the aromatic ring/aromatic heterocycle tert-butyl alcohol ester compound is obtained. The preparation method of the aromatic ring/aromatic heterocycle tert-butyl alcohol ester compound has the advantages that alkoxycarbonylation reaction on an aromatic heterocycle borate compound or aromatic ring boric acid compound is realized, and the aromatic ring/aromatic heterocycle tert-butyl alcohol ester compound is directly generated; raw materials are non-toxic, inexpensive and available; a catalytic system is low in cost and has good stability and broad applicability; reaction conditions are mild, safety is high, and control is easy; a technology is simple, operation is easy, environmental friendliness is realized, and specificity is strong, so that the preparation method of the aromatic ring/aromatic heterocycle tert-butyl alcohol ester compound is applicable to industrialized production.
- -
-
Paragraph 0188-0195
(2017/02/02)
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- An efficient method for the preparation of: Tert -butyl esters from benzyl cyanide and tert -butyl hydroperoxide under the metal free condition
-
A novel protocol to synthesize tert-butyl esters from benzyl cyanides and tert-butyl hydroperoxide has been successfully achieved. In the presence of tert-butyl hydroperoxide, Csp3-H bond oxidation, C-CN bond cleavage and C-O bond formation proceeded smoothly in one pot under the metal-free condition.
- Chen, Xiuling,Li, Yan,Wu, Minghu,Guo, Haibing,Jiang, Longqiang,Wang, Jian,Sun, Shaofa
-
p. 102023 - 102027
(2016/11/09)
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- A direct and sustainable synthesis of tertiary butyl esters enabled by flow microreactors
-
Tertiary butyl esters find large applications in synthetic organic chemistry. A straightforward method for the direct introduction of the tert-butoxycarbonyl group into a variety of organic compounds has been developed using flow microreactor systems. The resultant flow process was more efficient, versatile and sustainable compared to the batch.
- Degennaro, Leonardo,Maggiulli, Daniela,Carlucci, Claudia,Fanelli, Flavio,Romanazzi, Giuseppe,Luisi, Renzo
-
supporting information
p. 9554 - 9557
(2016/08/01)
-
- Metal-free, room-temperature, radical alkoxycarbonylation of aryldiazonium salts through visible-light photoredox catalysis
-
The first radical alkoxycarboxylation of aryldiazonium salts using CO gas through visible-light-induced photoredox catalysis (16 W blue LEDs) has been developed. This reaction is entirely metal-free, is carried out at room temperature with a low loading of an organic dye as a photocatalyst (0.5 mol%), and provides a wide range of arylcarboxylic acid esters in high yields. Importantly, this photocatalytic system can be successfully extended to other carboxylation reactions.
- Guo, Wei,Lu, Liang-Qiu,Wang, Yue,Wang, Ya-Ni,Chen, Jia-Rong,Xiao, Wen-Jing
-
supporting information
p. 2265 - 2269
(2015/02/19)
-
- Intramolecular rearrangement of α-azidoperoxides: An efficient synthesis of tert-butyl esters
-
An unprecedented intramolecular rearrangement of α-azidoperoxides, promoted by simple organic base to provide tert-butyl esters, has been presented. Further, a one-pot methodology consisting of in situ generation of the α-azidoperoxides from corresponding aldehydes followed by base-promoted rearrangement to obtain the desired ester has also been executed. Relevant mechanistic studies, to provide the proof for intramolecular alkoxy transfer, are investigated.
- Pramanik, Suman,Reddy, Reddy Rajasekhar,Ghorai, Prasanta
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p. 1393 - 1396
(2015/03/30)
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- Metal-free carbonylations by photoredox catalysis
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The synthesis of benzoates from aryl electrophiles and carbon monoxide is a prime example of a transition-metalcatalyzed carbonylation reaction which is widely applied in research and industrial processes. Such reactions proceed in the presence of Pd or Ni catalysts, suitable ligands, and stoichiometric bases. We have developed an alternative procedure that is free of any metal, ligand, and base. The method involves a redox reaction driven by visible light and catalyzed by eosin Y which affords alkyl benzoates from arene diazonium salts, carbon monoxide, and alcohols under mild conditions. Tertiary esters can also be prepared in high yields. DFT calculations and radical trapping experiments support a catalytic photoredox pathway without the requirement for sacrificial redox partners.
- Majek, Michal,Von Wangelin, Axel Jacobi
-
supporting information
p. 2270 - 2274
(2015/02/19)
-
- A mesoporous organosilica grafted Pd catalyst (MOG-Pd) for efficient base free and phosphine free synthesis of tertiary butyl esters via tertiary-butoxycarbonylation of boronic acid derivatives without using carbon monoxide
-
A mesoporous organosilica grafted palladium(ii) catalyst was synthesized and characterized using various spectroscopic techniques. Its catalytic activity was evaluated for the synthesis of tertiary butyl esters via tert-butoxycarbonylation of boronic acid
- Ghosh, Kajari,Molla, Rostam Ali,Iqubal, Md. Asif,Islam
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p. 3540 - 3551
(2015/06/25)
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- Copper-mediated oxidative homocoupling and rearrangement of N-alkoxyamides: An efficient method for the preparation of aromatic esters
-
N-Alkoxyamides are successfully converted into their corresponding esters in a moderate to satisfactory yields via copper-catalyzed oxidative homocoupling and Heron rearrangement. The process tolerates a wide variety of functional groups and allows the synthesis of sterically hindered ester products not readily accessible by traditional acylation chemistry. A radical-mediated pathway has been tentatively proposed for the oxidative process.
- Duan, Xiyan,Yang, Kun,Tian, Shuang,Ma, Junying,Li, Yaning,Zou, Jiao,Zhang, Dongliang,Cui, Huanqing
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p. 4634 - 4637
(2015/07/08)
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- Preparation of tert-butyl esters via Pd-catalyzed tert-butoxycarbonylation of (hetero)aryl boronic acid derivatives
-
A novel protocol to synthesize tert-butyl esters from boronic acids or boronic acid pinacol esters and di-t-butyl dicarbonate has been successfully achieved. The cross-coupling reactions can produce up to 94% yields by using palladium acetate and triphenylphosphine as catalyst system, dioxane as a solvent. Moreover, a wide range of substrates including benzenes, pyridines, and quinolines boronic acids or boronic acid pinacol esters can fit with this system as well.
- Wu, Yusheng,Li, Xinjian,Zou, Dapeng,Zhu, Helong,Wang, Yaping,Li, Jingya,Wu, Yangjie
-
supporting information
p. 1836 - 1839
(2014/05/06)
-
- Direct N-acylation of azoles via a metal-free catalyzed oxidative cross-coupling strategy
-
The KI-catalyzed N-acylation of azoles via direct oxidative coupling of C-H and N-H bonds has been developed. It could be smoothly scaled up to gram synthesis of acyl azoles. The reaction occurred by the coupling of acyl radicals and azoles to form the acyl azole radical anion, followed by its further oxidation. This journal is the Partner Organisations 2014.
- Zhao, Jingjing,Li, Pan,Xia, Chungu,Li, Fuwei
-
supporting information
p. 4751 - 4754
(2014/05/06)
-
- Copper-catalyzed oxidative esterification of aldehydes with dialkyl peroxides: Efficient synthesis of esters of tertiary alcohols
-
Copper-catalyzed oxidative esterification of aldehydes with dialkyl peroxides has been developed. This protocol affords a novel approach for the synthesis of carboxylic esters of tertiary alcohols under mild conditions. Depending on the catalyst system, a variety of tertiary esters were produced in good to excellent yields.
- Zhu, Yefeng,Wei, Yunyang
-
p. 13668 - 13670
(2013/08/23)
-
- Competition of C-H and C-O fragmentation in substituted p-methoxybenzyl ether radical cations generated by photosensitized oxidation
-
Laser and steady-state photolysis, sensitized by 2,4,6-triphenylpyrylium tetrafluoroborate (TPP+BF4-), of 4-methoxybenzyl ethers [4-CH3O-C6H4CH(OR 1)R, 1a: R = H, R1 = CH3; 1b: R = H, R 1 = C(CH3)3; 1c: R = CH3, R 1 = C(CH3)3; 1d: R = 4-CH3O-C 6H4, R1 = CH3] was carried out in CH3CN in the presence of oxygen. In particular, steady-state irradiation of 1a, b and d produced benzylic alcohols (together with a small amount of acetamide for 1a and 1b) and the oxidation carbonyl compounds (esters and ketones); 4-methoxy-α-methylbenzyl alcohol was the only product observed with 1c. Time-resolved investigations of 1c and 1d gave evidence of the intermediate benzylic carbocation, coming from the ether radical cation formed within the laser pulse by an electron transfer process from the ether to the TPP+ excited state. These results suggested that, besides the deprotonation of the benzyl carbon, the cleavage of the C-OR1 bond is also operative in the reaction pathways of the ether radical cation. The comparison of these results with those obtained in the photolysis of 1c with the uncharged 9,10-dicyanoanthracene (DCA) upholds a particular behavior of TPP+BF4-, probably due to the specific electrostatic interactions of BF4- with the radical cation. This is also supported by quantum mechanical calculation results performed at the B3LYP/6-31G(d) level to obtain the charge and spin density distributions of radical cations, free and complexed with BF4 -.
- Carlotti, Benedetta,Del Giacco, Tiziana,Elisei, Fausto
-
p. 489 - 499
(2013/07/11)
-
- Fe3O4 supported Pd(0) nanoparticles catalyzed alkoxycarbonylation of aryl halides
-
This paper describes the simple and efficient method for the alkoxycarbonylation of aryl iodides using magnetically recoverable Pd/Fe 3O4 as the catalyst under atmospheric pressure of carbon monoxide. Various aryl iodides on alkoxycarbonylation with alcohols gave the corresponding products in good to excellent yields. The catalyst is completely recoverable with the simple application of an external magnetic field, and the efficiency of the catalyst remains unaltered even after five cycles.
- Siva Prasad, Aviraboina,Satyanarayana, Bollikonda
-
p. 205 - 209
(2013/04/23)
-
- An efficient method for the preparation of tertiary esters by palladium-catalyzed alkoxycarbonylation of aryl bromides
-
The palladium-catalyzed alkoxycarbonylation of aryl bromides is described for the efficient preparation of tertiary esters. The protocol proved compatible with a wide variety of functionalized (hetero)aromatic bromides, as well as several different sterically hindered tertiary alcohols, affording the alkoxycarbonylated products in high yields. Finally, the formation of aromatic trityl esters is discussed.
- Xin, Zhuo,Gogsig, Thomas M.,Lindhardt, Anders T.,Skrydstrup, Troels
-
supporting information; experimental part
p. 284 - 287
(2012/02/16)
-
- Transition-metal-free alkoxycarbonylation of aryl halides
-
Transitions: The title reaction has been developed for the synthesis of a variety of tert-butyl benzoates by employing 1,10-phenanthroline as an additive. Various functional groups were tolerated and heteroaryl iodides were also suitable substrates. Preli
- Zhang, Hua,Shi, Renyi,Ding, Anxing,Lu, Lijun,Chen, Borui,Lei, Aiwen
-
supporting information
p. 12542 - 12545
(2013/02/23)
-
- Synthesis of tert-butyl peroxyacetals from benzyl, allyl, or propargyl ethers via iron-promoted C-H bond functionalization
-
When benzyl, allyl, and propargyl ethers were treated with tert-butyl hydroperoxide and a catalytic amount of iron(III) acetylacetonate, tert-butyl peroxyacetals were produced in good to excellent yields, via C-H bond functionalization. This method is also applicable to ethylene acetals of unsaturated aldehydes to give peroxyorthoesters.
- Iwata, Satoshi,Hata, Takeshi,Urabe, Hirokazu
-
supporting information
p. 3480 - 3484
(2013/02/22)
-
- Base-induced mechanistic variation in palladium-catalyzed carbonylation of aryl iodides
-
A mechanism, which is distinct from the traditional one when sodium alkoxide was used instead of tertiary amines, was proposed for the alkoxycarbonylation of aryl iodides. The catalytic cycle was composed of oxidative addition, subsequent ArPdOR formation, CO insertion to Pd-OR, and final reductive elimination of ArPdCOOR. The kinetic simultaneity of the formation of deiodinated side product from the aryl iodide and aldehyde from corresponding alcohol provided strong evidence for the existence of ArPdOR species. The observation of thioether, as the other competitive product in palladium catalyzed thiocarbonylation of aryl iodides and sodium alkylthiolate, also indicate the possibility of metathesis between ArPdl and sodium alkylthiolate. Preliminary kinetic studies revealed that neither oxidative addition nor reductive elimination was rate limiting. DFT calculation displayed preference for CO insertion into Pd-OR bond. The advantage of this novel mechanism had been demonstrated in the facile alkoxycarbonylation and thiocarbonylation. The ethoxycarbonylation of aryl iodides under room temperature and balloon pressure of CO in the presence of EtONa were examined, and good to high yields were obtained; the t-butoxycarbonylation reactions in the presence of t-BuONa were achieved, and the alkylthiocarbonylation (including the t-butylthiocarbonylation) of aryl iodides in the presence of sodium alkylthiolate were also investigated.
- Hu, Yanhe,Liu, Jing,Lu, Zhixin,Luo, Xiancai,Zhang, Heng,Lan, Yu,Lei, Aiwen
-
supporting information; experimental part
p. 3153 - 3158
(2010/05/15)
-
- Microwave-assisted carbonylation and cyclocarbonylation of aryl iodides under ligand free heterogeneous catalysis
-
"Chemical Equation Presented" Carbonylation reaction is a very effective transformation for the synthesis of esters, amides, and heterocyclic compounds. Heterogeneous catalyzed carbonylation reactions can be carried out using the association of Pd/C and microwave dielectric heating. Alkoxy carbonylation can be performed, with stoichiometric amounts of different primary and secondary alcohols in DMF in the presence of DBU as the base. Analogously, iodobenzene, CO, and amines can be transformed into the corresponding amides in good yields after a simple filtration to remove the catalyst. Pd/C was also successfully employed in microwave-assisted cyclocarbonylation of o-iodoaniline with acyl chlorides to give benzoxazinones. Pd/ C can be recycled two times without, a considerable difference in the reaction yields.
- Salvadori, Jessica,Balducci, Evita,Zaza, Silvia,Petricci, Elena,Taddei, Maurizio
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experimental part
p. 1841 - 1847
(2010/06/11)
-
- Esters as acylating reagent in a Friedel-Crafts reaction: Indium tribromide catalyzed acylation of arenes using dimethylchlorosilane
-
(Chemical Equation Presented) The Friedel-Crafts acylation of arenes with esters by dimethylchlorosilane and 10 mol % of indium tribromide has been achieved. The key intermediate RCOOSi(Cl)Me2 is generated from alkoxy esters with the evolution of the corresponding alkanes. The scope of the alkoxy ester moiety was wide: tert-butyl, benzyl, allyl, and isopropyl esters were successful. In addition, we demonstrated the direct synthesis of the indanone intermediate 11 of salviasperanol from ester 10.
- Nishimoto, Yoshihiro,Babu, Srinivasarao Arulananda,Yasuda, Makoto,Baba, Akio
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supporting information; experimental part
p. 9465 - 9468
(2009/04/06)
-
- An efficient protocol for the acylation of t-butanol in the presence of samarium diiodide
-
Samarium diiodide (SmI2) promotes the rapid acylation of t-butanol with a variety of acid chlorides under neutral conditions to afford cleanly the corresponding t-butyl esters in excellent yields.
- Jia, Xueshun,Zhu, Li,Li, Qing,Li, Jian,Li, Dafeng,Li, Shaoyu
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p. 203 - 204
(2008/02/11)
-
- Solvent polarity and organic reactivity in mixed solvents: Evidence using a reactive molecular probe to assess the role of preferential solvation in aqueous alcohols
-
(Chemical Equation Presented) Product selectivities [S = ([ester product]/[acid product]) x ([water]/[alcohol solvent])] are reported for solvolyses of p-methoxybenzoyl chloride (2) in aqueous methanol, ethanol, 2,2,2-trifluoroethanol, n-propyl alcohol, isopropyl alcohol, and tert-butyl alcohol at 25, 35, and 45°C. S values are small and depend significantly on the alcohol cosolvent, varying from 1.3 in methanol to 0.1 in tert-butyl alcohol, but S depends only slightly on the solvent composition, and on the temperature. As S adjusts the product ratios for changes in bulk solvent compositions, it is suggested that preferential solvation by either alcohol or water at the reaction site is not a major factor influencing rates or products. Logarithms of rates of solvolyses of 2 correlate well with Kosower Z values (based on solvatochromism). In contrast, another solvatochromic polarity index, ET(30), shows "dispersion" in correlations with the solvent ionizing power parameter, YOTs, probably due to aromatic ring and other solvation effects.
- Bentley, T. William,Ebdon, David N.,Kim, Eun-Ju,In, Sun Koo
-
p. 1647 - 1653
(2007/10/03)
-
- A new reagent for the convenient synthesis of t-butyl esters from t-butanol
-
An alumina-supported reagent has been prepared to synthesize the t-butyl esters from t-butanol. The method requires less time, mild conditions, and involves simplified work-up. Yield of the products is also high.
- Karmakar,Das
-
p. 535 - 537
(2007/10/03)
-
- A mild and selective method for the cleavage of tert-butyl esters
-
A method for the cleavage of t-butyl esters using silica gel in refluxing toluene is reported. Good yields of the corresponding carboxylic acids are obtained, and the reaction is selective for t-butyl esters over t-butyl ethers and trimethylsilylethyl (TMSE) esters.
- Jackson, Randy W
-
p. 5163 - 5165
(2007/10/03)
-
- Direct conversion of acylsilanes to esters mediated by iron (III) and nitrate ions
-
Acylsilanes, RC(O)SiMe3 (R = C6H5, p-MeOC6H4 and C5H11), can be converted into their corresponding carboxylic acids, when water is used as solvent, and esters when alcohol is used as solvent. This oxidation is mediated by iron (III) ions in 20-24 h or nitric acid diluted in alcohol in 2-10 h at room temperature.
- Patrocinio, Amauri F.,Moran, Paulo J. S.
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p. 1419 - 1423
(2007/10/03)
-
- 'New' catalysts for the ester-interchange reaction: The role of alkali-metal alkoxide clusters in achieving unprecedented reaction rates
-
The catalytic effect of alkali-metal tert-butoxide clusters on the rate of ester interchange for several pairs of esters has been determined in nonpolar and weakly polar solvents. Reactivities increase in the order (Li+ + + + +) with the fastest rates reaching 107 catalytic turnovers per hour (TO/h). Ester interchange rates were sensitive to the size of both the transferring OR groups and the ester substituent. Phenyl esters did not exchange with aliphatic esters due to nonstatistical breakdown patterns in the tetrahedral intermediate. A first-order equilibration analysis on the interchange between tert-butyl acetate (tBuAc) and methyl benzoate (MeBz) (5 mol % NaOtBu) indicated enhanced reaction rates as the reaction proceeded. Isolation and quenching (DCl/D2O) of precipitated catalyst points to a mechanism whereby sequential methoxy incorporation into the catalyst cluster increases activity, but eventually precipitates out of solution as a 3:1 OMe:OtBu cluster. The rate law was determined to be k(obs)[MeBz]1[tBuAc]0[NaOtBu](x), where x = 1.2(1), 1.4(1), and 0.85(1) in hexane, ether, and THF, respectively, under conditions where tetrameric catalyst aggregates are expected. Reaction rates were generally observed to be higher in nonpolar solvents (hexane > toluene, ether > THF). Eyring analysis over a 40°C range yielded ΔH(≠) = 10.0(1) kcal mol-1 and ΔS(≠) = -32(3) eu. A Hammett (σ) plot generated with para-substituted methyl benzoates gave ρ +2.35 (R 0.996). These results are interpreted in terms of a catalytic cycle composed of two coupled transesterification reactions with a turnover-limiting addition of a tert-butoxy-containing cluster (tetramer) to methyl benzoate. Catalyst relative reactivities (Cs+ > Rb+ > K+ > Na+ > Li+) are interpreted in terms of competitive electrostatic interactions between the alkali-metal and ground-state and transition-state anions. This analysis predicts the observed linear dependence between log(k(obs)) and l/r(ionic).
- Stanton, Matthew G.
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p. 5981 - 5989
(2007/10/03)
-
- Convenient preparations of t-butyl esters and ethers from t-butanol
-
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)
-
- Oxidation of Benzaldehydes Catalyzed by Methyltrioxorhenium with Hydrogen Peroxide
-
Methyltrioxorhenium-catalyzed oxidation of benzaldehydes with hydrogen peroxide gives corresponding phenols in good yield.Benzaldehydes substituted with methoxy or hydroxyl groups at 2- and/or 4-position are good substrates for this reaction.
- Yamazaki, Shigekazu
-
p. 127 - 128
(2007/10/02)
-
- A NEW METHOD FOR THE PREPARATION OF TERTIARY BUTYL ETHERS AND ESTERS
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T-butyl 2,2,2-trichloroacetimidate (1), readily prepared by addition of t-butanol to trichloroacetonitrile, is an efficient reagent for the preparation of t-butyl ethers and esters in the presence of a catalytic amount of boron trifluoride etherate.
- Armstrong, Alan,Brackenridge, Ian,Jackson, Richard F.W.,Kirk, Joanna M.
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p. 2483 - 2486
(2007/10/02)
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- NOVEL OXIDATIVE CLEAVAGE OF CARBON-CARBON BOND IN HYDRAZONES BY OXYGENATION WITH COBALT SCHIFF BASE COMPLEX
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Oxygenation of aromatic ketone hydrazones with Co(salen) in methanol resulted unexpectedly in oxidative degradation to give methyl benzoate derivatives.A mechanism involving nucleophilic attack by methanol on a diazo intermediate is discussed.
- Nishinaga, Akira,Yamazaki, Shigekazu,Matsuura, Teruo
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p. 2649 - 2652
(2007/10/02)
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- Copper Ion Promoted Esterification of S-2-Pyridyl Thioates and 2-Pyridyl Esters. Efficient Methods for the Preparation of Hindered Esters
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The esterification of the S-2-pyridyl thioates and 2-pyridyl esters with alcohols in acetonitrile is greatly facilitated by the addition of cupric bromide and copper ion is observed to catalyze the reaction.The ester formation is found to be sensitive to solvents, metal salts, and reaction temperatures.The esterification of S-2-pyridyl thioates is much more rapid than the esterification of 2-pyridyl esters under the reaction conditions employed.This method is exceedingly effective in the preparation of sterically hindered esters and has advantages over known methods in many respects such as high yields, the mildness of the reaction, and the rapidity of the reaction.
- Kim, Sunggak,Lee, Jae In
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p. 1712 - 1716
(2007/10/02)
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- An Improved and Convenient Synthesis of Esters Using 1,1'-Carbonyldiimidazole and a Reactive Halide
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The esterification of carboxylic acid proceeded easily in a one-pot reaction with 1,1'-carbonyldiimidazole in the presence of a reactive halide under neutral reaction conditions in high yields. Keywords - esterification: 1,1'-carbonyldiimidazole; formylation; tert-butyl ester; imidazolium salt; one-pot reaction
- Kamijo, Tetsuhide,Harada, Hiromu,Iizuka, Kinji
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p. 5044 - 5047
(2007/10/02)
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- PALLADIUM(0) AND RHODIUM(I) CATALYSIS OF THE CARBONYLATION OF UNACTIVATED BROMIDES
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Alkyl, vinyl, and aromatic bromides react with organoborates and carbon monoxide, in the presence of catalytic quantities of 1,5-hexadienerhodium(I) chloride dimer and tetrakis(triphenylphosphine)palladium(0), to give carboxylic esters in good yields.
- Hashem, Khaled E.,Woell, James B.,Alper, Howard
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p. 4879 - 4880
(2007/10/02)
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