- Gold-Catalyzed [3+2]-Annulations of α-Aryl Diazoketones with the Tetrasubstituted Alkenes of Cyclopentadienes: High Stereoselectivity and Enantioselectivity
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This work reports gold-catalyzed [3+2]-annulations of α-diazo ketones with highly substituted cyclopentadienes, affording bicyclic 2,3-dihydrofurans with high regio- and stereoselectivity. The reactions highlights the first success of tetrasubstituted alkenes to undergo [3+2]-annulations with α-diazo carbonyls. The enantioselective annulations are also achieved with high enantioselectivity using chiral forms of gold and phosphoric acid. Our mechanistic analysis supports that cyclopentadienes serve as nucleophiles to attack gold carbenes at the more substituted alkenes, yielding gold enolates that complex with chiral phosphoric acid to enhance the enantioselectivity.
- Chen, Ching-Nung,Cheng, Wei-Min,Wang, Jian-Kai,Chao, Tzu-Hsuan,Cheng, Mu-Jeng,Liu, Rai-Shung
-
supporting information
p. 4479 - 4484
(2021/01/21)
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- Aryl C-F bond functionalization preparation method
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The invention relates to the technical field of organic compound synthesis, in particular to an aryl C-F bond functionalization preparation method. A fluorobenzene compound and a nucleophilic reagent react under the action of a composite catalyst, wherein the composite catalyst is formed by mixing a visible light catalyst and a metal catalyst. The photocatalyst is adopted, the reaction process is safe and controllable, and operation in the preparation and production process is simplified; a purple LED is used as a reaction energy source and is green and environment-friendly, the energy utilization rate is high, and conversion from light energy to chemical energy can be efficiently realized; in the reaction, a simple nucleophilic reagent is used for attacking free radical cation species generated under a visible light catalysis condition, so that a target product with an extremely wide range is efficiently and greenly prepared; the operation steps are simplified, and the reaction route is shortened; and moreover, the forward reaction rate is high, and the production efficiency is remarkably improved.
- -
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Paragraph 0052; 0089-0093; 0117-0121
(2021/09/29)
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- Asymmetric Catalytic Epoxidation of Terminal Enones for the Synthesis of Triazole Antifungal Agents
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An enantioselective epoxidation of α-substituted vinyl ketones was realized to construct the key epoxide intermediates for the synthesis of various triazole antifungal agents. The reaction proceeded efficiently in high yields with good enantioselectivities by employing a chiral N,N′-dioxide/ScIII complex as the chiral catalyst and 35% aq. H2O2 as the oxidant. It enabled the facile transformation for optically active isavuconazole, efinaconazole, and other potential antifungal agents.
- Feng, Xiaoming,He, Qianwen,Liu, Xiaohua,Zhang, Dong,Zhang, Fengcai
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supporting information
p. 6961 - 6966
(2021/09/11)
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- Bromomethyl Silicate: A Robust Methylene Transfer Reagent for Radical-Polar Crossover Cyclopropanation of Alkenes
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A general protocol for visible-light-induced cyclopropanation of alkenes was developed with bromomethyl silicate as a methylene transfer reagent, offering a robust tool for accessing highly valuable cyclopropanes. In addition to α-aryl or methyl-substituted Michael acceptors and styrene derivatives, the unactivated 1,1-dialkyl ethylenes were also shown to be viable substrates. Apart from realizing the cyclopropanation of terminal alkenes, the methyl transfer reaction has been further demonstrated to be amenable to the internal olefins. The photocatalytic cyclopropanation of 1,3-bis(1-arylethenyl)benzenes was also achieved, giving polycyclopropane derivatives in excellent yields. With late-stage cyclopropanation as the key strategy, the synthetic utility of this transformation was also demonstrated by the total synthesis of LG100268.
- Luo, Wenping,Fang, Yewen,Zhang, Li,Xu, Tianhang,Liu, Yongjun,Li, Yan,Jin, Xiaoping,Bao, Jiakan,Wu, Xiaodong,Zhang, Zongyong
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supporting information
p. 1778 - 1781
(2020/03/11)
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- Direct Synthesis of Propen-2-yl Sulfones through Cascade Reactions Using Calcium Carbide as an Alkyne Source
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A simple method for the construction of propen-2-yl sulfones through cascade reactions of calcium carbide with arylsulfonylhydrazones using copper as a mediator is described. The salient features of this protocol are the use of readily available and easy-to-handle alkyne source, broad substrate scope, open-air condition, and simple operation procedure.
- Gao, Lei,Liu, Zhenrong,Ma, Xiaolong,Li, Zheng
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supporting information
p. 5246 - 5250
(2020/07/04)
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- Iron powder and tin/tin chloride as new reducing agents of Meerwein arylation reaction with unexpected recycling to anilines
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Simple and rapid route for Meerwein arylation reaction using iron powder or a mixture of tin/tin chloride has been developed. In the presence of iron powder, different aryl diazonium salts reacted with methyl vinyl ketone, acrylates, and isopropenyl acetate. Production of oximes was detected as the main product with acrylates or in a mixture with β-aryl methyl ketones in the case of methyl vinyl ketone. The in situ produced HNO2 from an excess of NaNO2/HCl was trapped by alkyl aryl radical to form oximes in the E configuration form. The presence of tin/tin chloride mixture in the reaction of the aryl diazonium salts with methyl vinyl ketone produced Michael products along with β-aryl methyl ketones. The predicted α-aryl methyl ketones from the reaction of isopropenyl acetate with the diazotized anilines were obtained using iron or tin/tin chloride mixture.
- Abdelwahab, Ahmed B.,El-Sawy, Eslam R.,Kirsch, Gilbert
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supporting information
p. 526 - 538
(2020/01/08)
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- Porphyrins as Photoredox Catalysts in Csp2-H Arylations: Batch and Continuous Flow Approaches
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We have investigated both batch and continuous flow photoarylations of enol-acetates to yield different α-arylated aldehyde and ketone building blocks by using diazonium salts as the aryl-radical source. Different porphyrins were used as SET photocatalysts, and photophysical as well as electrochemical studies were performed to rationalize the photoredox properties and suggest mechanistic insights. Notably, the most electron-deficient porphyrin (meso-tetra(pentafluorophenyl)porphyrin) shows the best photoactivity as an electron donor in the triplet excited state, which was rationalized by the redox potentials of excited states and the turnover of the porphyrins in the photocatalytic cycle. A two-step continuous protocol and multigram-scale reactions are also presented revealing a robust, cost-competitive, and easy methodology, highlighting the significant potential of porphyrins as SET photocatalysts.
- De Souza, Aline A. N.,Silva, Nathalia S.,Müller, Andressa V.,Polo, André S.,Brocksom, Timothy J.,De Oliveira, Kleber T.
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p. 15077 - 15086
(2019/01/03)
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- A method of preparing fluorine zuozuo fungus acid radical hydroxylamine (by machine translation)
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The present invention provides a method for preparing fluorine zuozuo fungus acid radical of hydroxylamine, which belongs to the field of the preparation of the original pharmaceutical compound. The invention relates to a method for the preparation of hydroxylamine fluorine zuozuo fungus acid radical, (1) will be to P-chloroaniline with isopropenyl acetate reaction, to obtain the 4 '- chlorophenyl acetone; (2) then benzene ring chlorination reaction, to obtain 2', 4 ', 6' - trichlorobenzene acetone; (3) to carry out the reduction reaction of carbonyl, to obtain 1 - (2 ', 4', 6 '- three-chlorophenyl) - 2 - propanol; (4) to hydroxy halogenated reaction to obtain 1 - (2', 4 ', 6' - three-chlorophenyl) - 2 - chloro propane; (5) with methoxamine amination reaction, to obtain the O - methyl N - [1 - methyl - 2 - (2, 4, 6 - tri-chlorophenyl) - ethyl] - hydroxylamine; (6) under the effect of the bonding agent in the step (5) with the product of 3 - difluoromethyl - 1 - methyl - 1 H - pyrazole - 4 - formyl chloride undergo the substitution reaction, to obtain the fluorine zuozuo fungus acid radical hydroxylamine. By improving the process for preparing fluorine zuozuo fungus acid radical hydroxylamine, change the intermediate synthetic route, avoid the traditional [...] cyano sodium borohydride reduction process, the production cost is reduced. (by machine translation)
- -
-
Paragraph 0020; 0028
(2018/10/19)
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- Salicylic Acid-Catalyzed Arylation of Enol Acetates with Anilines
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α-Aryl ketones are both structure moieties commonly found in bioactive compounds and versatile synthetic intermediates for the preparation of drug-like molecules. An operationally simple and scalable protocol has been developed to prepare α-aryl ketones from readily available aromatic amines and enol acetates (or silyl enol ethers). This metal-free methodology features the use of salicylic acid as a convenient catalyst to promote the formation of aryl radicals from in-situ generated aryl diazonium salts, without demanding thermal or photochemical activation. The mild reaction conditions used are compatible with anilines substituted with diverse functionalities. Structural elaboration of some prepared α-aryl ketones was accomplished to illustrate their usefulness as building blocks. (Figure presented.).
- Felipe-Blanco, Diego,Gonzalez-Gomez, Jose C.
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supporting information
p. 2773 - 2778
(2018/07/29)
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- Application of piperidine-containing thiazole compound and preparation method thereof
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The invention discloses application of a piperidine-containing thiazole compound as a bactericide in controlling cucumber downy mildew and rice sheath blight, and a preparation method of the piperidine-containing thiazole compound. The invention provides a novel application of the piperidine-containing thiazole compound. The compound is a new compound with bactericidal activity and provides a foundation for the research and development of piperidine thiazole pesticides. The preparation method of the invention provides a raw material foundation for the preparation of a bactericide.
- -
-
Paragraph 0006; 0014
(2018/04/02)
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- A convenient and efficient one-pot synthesis of arylacetones from (E)-3-aryl-2-methylacrylic acids by curtius rearrangement
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A convenient and efficient method was developed for the synthesis of arylacetones from (E)-3-aryl-2-methylacrylic acids through a Curtius rearrangement. The Curtius rearrangement of (E)-3-aryl-2-methylacryloyl azides and subsequent hydrolysis proceeded at mild temperatures in a two-phase medium of carbon tetrachloride and water containing a catalytic amount of tetrabutylammonium bromide to give the corresponding derivatives in 82-93% yield.
- He, Xin,Cao, Chong,Liang, Jingwei,Li, Xinyang,Zhang, Tingjian,Meng, Fanhao
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p. 386 - 390
(2017/02/10)
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- Enantioselective synthesis of β-substituted chiral allylic amines: Via Rh-catalyzed asymmetric hydrogenation
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An asymmetric mono-hydrogenation of 2-acetamido-1,3-dienes catalyzed by a Rh-DuanPhos complex has been developed. This approach provides easy access to chiral allylic amines with excellent enantioselectivities and high regioselectivities. The products are valuable chiral building blocks for pharmaceuticals.
- Wang, Qingli,Gao, Wenchao,Lv, Hui,Zhang, Xumu
-
supporting information
p. 11850 - 11853
(2016/10/07)
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- Metal-free, catalytic regioselective oxidative conversion of vinylarenes: A mild approach to phenylacetic acid derivatives
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A new synthetic approach towards the synthesis of phenylacetic acids from aromatic alkenes has been developed for the first time under mild conditions by employing non-toxic reagents such as molecular iodine and oxone. This metal-free catalytic regioselective oxygenation of vinylarenes proceeds via tandem iodofunctionalization/de-iodination induced rearrangement.
- Kodumuri, Srujana,Peraka, Swamy,Mameda, Naresh,Chevella, Durgaiah,Banothu, Rammurthy,Nama, Narender
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p. 6719 - 6723
(2016/02/03)
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- Anti-Markovnikov Oxidation of β-Alkyl Styrenes with H2O as the Terminal Oxidant
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Oxygenation of alkenes is one of the most straightforward routes for the construction of carbonyl compounds. Wacker oxidation provides a broadly useful strategy to convert the mineral oil into higher value-added carbonyl chemicals. However, the conventional Wacker chemistry remains problematic, such as the poor activity for internal alkenes, the lack of anti-Markovnikov regioselectivity, and the high cost and chemical waste resulted from noble metal catalysts and stoichiometric oxidant. Here, we describe an unprecedented dehydrogenative oxygenation of β-alkyl styrenes and their derivatives with water under external-oxidant-free conditions by utilizing the synergistic effect of photocatalysis and proton-reduction catalysis that can address these challenges. This dual catalytic system possesses the single anti-Markovnikov selectivity due to the property of the visible-light-induced alkene radical cation intermediate.
- Zhang, Guoting,Hu, Xia,Chiang, Chien-Wei,Yi, Hong,Pei, Pengkun,Singh, Atul K.,Lei, Aiwen
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supporting information
p. 12037 - 12040
(2016/09/28)
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- Hypoiodite-catalyzed regioselective oxidation of alkenes: An expeditious access to aldehydes in aqueous micellar media
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A highly anti-Markovnikov selective oxidation of alkenes based on in situ generated hypoiodite catalysis in aqueous micellar media under mild conditions has been described. This novel catalytic system realizes an efficient synthesis of aldehydes from alkenes in an economically viable and environmentally safe fashion. The preliminary mechanistic studies suggest that the reaction proceeds via tandem iodofunctionalization/1,2-aryl or alkyl migration. The scope and limitations of this tandem process are demonstrated with various mono- and disubstituted (terminal and internal) olefins.
- Swamy, Peraka,Reddy, Marri Mahender,Naresh, Mameda,Kumar, Macharla Arun,Srujana, Kodumuri,Durgaiah, Chevella,Narender, Nama
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p. 1125 - 1130
(2015/04/22)
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- A convenient catalytic oxidative 1,2-shift of arylalkenes for preparation of α-aryl ketones mediated by NaI
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Using a catalytic amount of NaI and a stoichiometric oxidant Oxone@, a convenient procedure has been developed for the catalytic oxidative 1,2-shift of arylalkenes in CH3CN/H2O at room temperature, which provides the corresponding α-aryl ketones in moderate to good yields. In this protocol, sodium iodide is first oxidized into hypoiodous acid, which reacts with arylalkene to afford iodohydrin. Then, the iodohydrin is transformed into the α-aryl ketone via an oxidative 1,2-shift rearrangement.
- Zhu, Min,Zhao, Yang
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p. 248 - 250
(2015/03/30)
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- Expedient Access to 2,3-Dihydropyridines from Unsaturated Oximes by Rh(III)-Catalyzed C-H Activation
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α,β-Unsaturated oxime pivalates are proposed to undergo reversible C(sp2)-H insertion with cationic Rh(III) complexes to furnish five-membered metallacycles. In the presence of 1,1-disubstituted olefins, these species participate in irreversible migratory insertion to give, after reductive elimination, 2,3-dihydropyridine products in good yields. Catalytic hydrogenation can then be used to convert these molecules into piperidines, which are important structural components of numerous pharmaceuticals.
- Romanov-Michailidis, Fedor,Sedillo, Kassandra F.,Neely, Jamie M.,Rovis, Tomislav
-
supporting information
p. 8892 - 8895
(2015/08/03)
-
- Pinacolatoboron fluoride (pinBF) is an efficient fluoride transfer agent for diastereoselective synthesis of benzylic fluorides
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The incorporation of alkoxy ligands within a range of alkoxyfluoroboranes and dialkoxyfluoroboranes results in fluoroborane reagents with attenuated Lewis acidity and increased ability to donate fluoride ion(s) when compared to boron trifluoride itself. Pinacolatoboron fluoride (pinBF), prepared in situ from BF3·OEt2 and bis(O-trimethylsilyl)pinacol, has been identified as an efficient fluoride donor which allows highly stereoselective SN1-type epoxide ring-opening (with retention of configuration) of a range of trans-β-methyl-substituted aryl epoxides to give the corresponding syn-fluorohydrins. The substrate scope of this transformation is more broad than the analogous protocol using boron trifluoride alone.
- Cresswell, Alexander J.,Davies, Stephen G.,Figuccia, Aude L.A.,Fletcher, Ai M.,Heijnen, Dorus,Lee, James A.,Morris, Melloney J.,Kennett, Alice M.R.,Roberts, Paul M.,Thomson, James E.
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p. 3373 - 3377
(2015/06/02)
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- Copper-catalyzed coupling of aryl iodides and tert-butyl keto esters: Efficient access to α-aryl ketones and α-arylacetic acid tert-butyl esters
-
CuI/trans-4-hydroxy-l-proline catalyzed coupling of aryl iodides with tert-butyl keto esters proceeded smoothly at 40 °C in DMF, providing α-aryl ketones after acid-promoted deprotection and decarboxylation of tert-butyl ester group. While CuI/2-picolinic acid catalyzed coupling of aryl iodides with tert-butyl acetoacetate at 70 °C in dioxane delivered α-arylacetic acid tert-butyl esters upon spontaneous deacylation. A wide range of functional groups, such as acetyl, methoxy, nitrile, nitro, bromo, and chloro were compatible with the reaction conditions.
- Zhao, Duo,Jiang, Yongwen,Ma, Dawei
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p. 3327 - 3332
(2014/05/06)
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- One-step synthesis of 1-chloro-3-arylacetone derivatives from arylacetic acids
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A practical one-step method has been developed to prepare α-chloroketones from readily available, inexpensive phenylacetic acid derivatives. The method utilizes the unique reactivity of an intermediate Mg.enolate dianion, which displays selectivity for the carbonyl carbon of chloromethyl carbonyl electrophiles. Decarboxylation of the intermediate occurs spontaneously during the reaction quench. The utility of the reaction products has been demonstrated through the total synthesis of the natural product cimiracemate B.
- Zacuto, Michael J.,Dunn, Robert F.,Figus, Margaret
-
supporting information
p. 8917 - 8925
(2015/01/09)
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- Manganese(IV)-mediated hydroperoxyarylation of alkenes with aryl hydrazines and dioxygen from air
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We report a new carbooxygenation-type version of the Meerwein arylation in which the introduction of oxygen is achieved by using dioxygen from the air. In this way, hydroperoxides were obtained from activated as well as non-activated alkenes by oxidizing aryl hydrazines with manganese dioxide. The best results were obtained with α-substituted acrylates. Importantly, the aryl hydrazine has to be added slowly to the reaction mixture to allow sufficient uptake of dioxygen from the air. Competition and labeling experiments revealed hydroperoxyl radicals as novel oxygen-centered radical scavengers. The introduction of oxygen into a Meerwein arylation has been achieved with dioxygen from air as an oxygen-centered radical scavenger. The slow addition of the aryl hydrazine is key to aryl radical formation through oxidation with manganese dioxide; whereby, hydroperoxides were obtained from activated as well as non-activated alkenes.
- Kindt, Stephanie,Jasch, Hannelore,Heinrich, Markus R.
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supporting information
p. 6251 - 6255
(2014/06/09)
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- Catalytic oxidative 1,2-shift in 1,1′-disubstituted olefins using arene(iodo)sulfonic acid as the precatalyst and oxone as the oxidant
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An efficient, catalytic hypervalent iodine-mediated oxidative 1,2-shift of 1,1′-disubstituted olefins is described. This methodology provides concise access to homobenzylic ketones with electron-donating substituents. In the case of cyclic systems, this transformation results in ring-expanded β-benzocycloalkanones, which are useful for further elaboration.
- Purohit, Vikram C.,Allwein, Shawn P.,Bakale, Roger P.
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supporting information
p. 1650 - 1653
(2013/06/27)
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- Palladium-catalyzed mono-α-arylation of acetone with aryl imidazolylsulfonates
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Set the ace(tone): A palladium catalyst derived from the bidentate XantPhos ligand and Pd(OAc)2 has enabled broadly applicable mono-α-arylations of acetone to be performed with air- and moisture-stable aryl imidazolylsulfonates as most user-friendly electrophiles (see scheme). Copyright
- Ackermann, Lutz,Mehta, Vaibhav P.
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supporting information; experimental part
p. 10230 - 10233
(2012/09/22)
-
- Visible-light-mediated α-arylation of enol acetates using aryl diazonium salts
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Visible light mediates efficiently the α-arylation of enol acetates by aryl diazonium salts under mild conditions using [Ru(bpy)3]Cl 2 as a photoredox catalyst. The broad scope of the reaction toward various diazonium salts and enol acetates was explored. The application of this reaction in the concise synthesis of 2-substituted indoles was demonstrated
- Hering, Thea,Hari, Durga Prasad,Koenig, Burkhard
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p. 10347 - 10352
(2013/01/15)
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- β-fluoroamphetamines via the stereoselective synthesis of benzylic fluorides
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A range of substituted aryl epoxides undergo efficient ring-opening hydrofluorination upon treatment with 0.33 equiv of BF3-OEt 2 in CH2Cl2 at -20 -°C to give the corresponding syn-fluorohydrins, consistent with a mechanism involving a stereoselective SN1-type epoxide ring-opening process. The benzylic fluoride products of these reactions are valuable templates for further elaboration, as demonstrated by the preparation of a range of aryl-substituted β-fluoroamphetamines.
- Cresswell, Alexander J.,Davies, Stephen G.,Lee, James A.,Roberts, Paul M.,Russell, Angela J.,Thomson, James E.,Tyte, Melloney J.
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supporting information; experimental part
p. 2936 - 2939
(2010/09/10)
-
- Copper catalyzed arylation/C-C bond activation: An approach toward α-aryl ketones
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An efficient arylation/C-C activation process was discovered. -Diketones with aryl halides (aryl iodides and aryl bromides) could undergo reaction smoothly in the presence of Cu(I) or Cu(II) salts in DMSO using K3 PO4 3H2 O without ligands. The role of H2 O was unprecedented, which assisted the C-C activation. Various -aryl ketones could be efficiently synthesized by this novel method. In situ monitoring of the formation of KOAc and experimentation relating to "a classic diagnostic technique for the participation of radical anion intermediates" revealed the preliminary mechanistic information for the reaction. This method is simple, general, and practical which complemented the classic method for the rapid construction of C-C bonds to a carbonyl moiety.
- He, Chuan,Guo, Sheng,Huang, Li,Lei, Aiwen
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supporting information; scheme or table
p. 8273 - 8275
(2010/08/03)
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- Et2Zn-mediated rearrangement of bromohydrins
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(Chemical Equation Presented) A simple and highly efficient method for the rearrangement of bromohydrins mediated by Et2Zn to synthesize carbonyl compounds was described. Various β-bromo alcohols were treated with 0.6 equiv of Et2Zn to form a zinc complex in CH 2Cl2 at room temperature for 2 h, followed by 1,2-migration to give the corresponding carbonyl compounds. This remarkable and clean rearrangement is general for acyclic and cyclic bromohydrins, and a variety of ring-expansive and -contractive carbonyl compounds were obtained in good to excellent yields according to the feature of the starting bromohydrins. The functional group tolerance of organozinc reagents in this reaction will be useful in organic synthesis. The scope and limitations of this rearrangement process were also investigated.
- Li, Lezhen,Cai, Peijie,Guo, Qingxiang,Xue, Song
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p. 3516 - 3522
(2008/09/20)
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- Spin trapping of alkoxyl radicals generated from 5-methyl and 5-aryl-3-alkoxy-4-methylthiazole-2(3H)-thiones in photochemically induced and microwave-initiated reactions
-
Methoxyl and isopropoxyl radicals were generated from N-alkoxy-4,5-dimethylthiazole-2(3H)-thiones (λmax~320 nm) and 5-aryl derivatives (aryl=p-XC6H4; X=MeO, H, AcNH, Cl) (λmax~335 nm) in photochemically and microwave-induced reactions. Alkoxyl radicals were trapped with dimethylpyrrolidine N-oxide and characterized as spin adducts via EPR. Cumyloxyl radicals were liberated in a similar manner from N-cumyloxy-5-(4-methoxyphenyl)-4-methylthiazole-2(3H)-thione. A noteworthy bathochromic shift was found for the lowest energy transition of N-(hydroxy)indeno[2,1-d]thiazole-2(3H)-thione (λmax=376 nm), if compared to the UV-vis absorption of N-hydroxy-4-methyl-5-phenylthiazole-2(3H)-thione (λmax=338 nm). Syntheses of alkoxyl radical precursors and procedures for conducting N,O-homolysis are described in a full account.
- Gro?, Andreas,Schneiders, Nina,Daniel, Kristina,Gottwald, Thomas,Hartung, Jens
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p. 10882 - 10889
(2008/12/23)
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- Alkyl radical generation in water under ambient conditions - A new look at the Guareschi reaction of 1897
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(Chemical Equation Presented) Chemical and biochemical significance of a long-forgotten 19th century observation: The hydrocarbon production from quaternary glutarimides on neutralization in water is the consequence of formation of alkyl radicals, which means that it is possible to generate alkyl radicals under very mild conditions. Oxygen trapping competes with hydrogen abstraction (see scheme).
- Nguyen, Bao,Chernous, Katya,Endlar, Daniel,Odell, Barbara,Piacenti, Michela,Brown, John M.,Dorofeev, Alexander S.,Burasov, Alexander V.
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p. 7655 - 7658
(2008/09/18)
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- A practical synthesis of α-aryl methyl ketones via a transition-metal-free Meerwein arylation
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We report herein a simple, scalable, transition-metal-free approach to the synthesis of α-aryl methyl ketones from diazonium tetrafluoroborate salts under mild conditions. This methodology uses easily accessible and nontoxic starting material and was applied to the multi-kilogram-scale preparation of 1-(3-bromo-4-methylphenyl)propan-2-one.
- Molinaro, Carmela,Mowat, Jeffrey,Gosselin, Francis,O'Shea, Paul D.,Marcoux, Jean-Francois,Angelaud, Remy,Davies, Ian W.
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p. 1856 - 1858
(2007/10/03)
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- Oxidative rearrangements of arylalkenes with [hydroxy(tosyloxy)iodo]benzene in 95% methanol: A general, regiospecific synthesis of α-aryl ketones
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The treatment of arylalkenes with [hydroxy(tosyloxy)iodo]benzene in 95% methanol affords the corresponding α-aryl ketones. This oxidative rearrangement is general for acyclic and cyclic arylalkenes and permits regioselective syntheses of isomeric α-phenyl ketone pairs.
- Justik, Michael W.,Koser, Gerald F.
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p. 6159 - 6163
(2007/10/03)
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- An Effective System to Synthesize Arylacetones. Substrate-ionic Liquid-ultrasonic Irradiation
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Manganese(III) acetate-promoted aromatic acetonylation has been accomplished with ultrasonic irradiation in ionic liquids, [N-n-pentyl-4- picolinium] [closo-CB11H12] (1), [OMIM] [BF4] and [BMIM] [PF6] in 62-93% yields, with excellent chemical selectivity.
- Yinghuai, Zhu,Bahnmueller, Stefan,Hosmane, Narayan S.,Maguire, John A.
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p. 730 - 731
(2007/10/03)
-
- Reactions of aldehydes with polymer-supported selenoalkylidenetriphenylphosphoranes. A facile method for the synthesis of carbonyl compounds
-
The transylidation reactions of polymer-bound selenium bromide with alkylidenetriphenylphosphoranes 1 gave resin 2, which is sufficiently reactive to undergo Wittig-type reactions to afford the vinylic selenide resins 3. Cleavage gave ketones and aldehydes under different conditions.
- Huang, Xian,Sheng, Shou-Ri
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p. 9035 - 9037
(2007/10/03)
-
- A facile procedure for the conversion of nitroolefins into carbonyl compounds using Al-NiCl2·6H2O-THF system
-
It has been demonstrated that a variety of nitroolefins can be efficiently converted into the corresponding carbonyl compounds by the reaction with an Al-NiCl2.6H2O-THF system.
- Bezbarua, Maitreyee S.,Bez, Ghanashyam,Barua, Nabin C.
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p. 325 - 326
(2007/10/03)
-
- The Zinc-Trifluoroacetic Acid Reaction in Organic Solvents: A Facile Procedure for the Conversion of Nitroolefins into Carbonyl Compounds under Mild Conditions
-
It has been demonstrated that nitroolefins are efficiently converted into the corresponding carbonyl compounds by reaction with stoichiometric amounts of zinc and trifluoroacetic acid in organic solvents like DMF, methanol etc.
- Saikia, Anil K.,Barua, Nabin C.,Sharma, Ram P.,Ghosh, Anil C.
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p. 124 - 125
(2007/10/03)
-
- Is Selective Monosubstitution of Dihalides via SRN1 Reaction Feasible? An Electrochemical Approach for Dichloroarenes
-
1,4-Dichlorobenzene and dichloropyridines undergo SRN1 reaction with various nucleophiles upon electrochemical initiation.Substitution can compete with reduction only when indirect electrolyses at low current are performed.Selective formation of monosubstitution products is observed when the nucleophiles used behave as electron-donating groups when attached to the aromatic moiety, a situation which is just the opposite of what had been observed when the same reactions were initiated photochemically.This surprising difference in behavior can be rationalized in terms of different capabilities of both activation methods to generate the key monosubstitution anion radical, ArNuX(.-).Kinetic and thermodynamic data concerning the reactivity of dichloroarenes in such processes are presented and discussed.
- Amatore, Christian,Combellas, Catherine,Lebbar, Nour-Eddine,Thiebault, Andre,Verpeaux, Jean-Noel
-
-
- Mass spectrometric investigations on phenylacetic acid derivatives, IV: Loss of ortho-substituents from ionized phenyl-2-propanones upon electron impact
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In the gas phase, the phenyl-2-propanone molecules 2a-4a lose upon electron impact chloro-, bromo-, and iodo-radicals specifically at the orthopOsition of the phenyl group giving rise to strong (M-Hal.)+-ions (70/12 eV; 1st and 2nd FFR) of identical structure as confirmed by their MIKE-CAD-spectra. The daughter ions at m/z 133 from o-chlorophenyl-2-propanone (2a) and 2,2-dimethyl-2,3-dihydro[b]furane (11) are structurally similar but not identical (similarity index 99.8). The collisionally activated (2nd FFR) (M-Br.)+-ions from o-bromophenyl-2-propanone (3a) and 1-bromo-1-phenyl-2-propanone (12) produce virtually congruent spectra. The most impOrtant subsequent fragmentation of the (M-Hal-)+-ions from 2a-4a is the loss of CO which incorporates the C-atom of the carbonyl group exclusively (13C labelling). Mechanistic aspects of the fragmentation sequences are discussed (Figs. 5 and 8).
- Striegel,Mayer,Wiegrebe,Schlunegger,Siegrist,Aebi
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p. 751 - 760
(2007/10/02)
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- SYNTHESIS, TAUTOMERIZATION AND ACYLATION OF 1-PHENYLPROPANE-2-IMINES
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1-Phenylpropane-2-imines and its derivatives substituted in a benzene ring were synthesized in reaction of proper ketones with ammonia.The keto-enol and imine-enamine tautomerisms in starting compounds and reaction products, respectively, were examined by proton nuclear magnetic resonance spectrometry and chemical methods.The determined constants of tautomeric equilibria were correlated with the Hammett ? constants.Electronic effects occurring in the systems under study were discussed basing on the correlations found.A possible use of 1-phenylpropane-2-imines in synthesis of N-acyl derivatives of 2-phenyl-1-methylvinylamines was examined.
- Zielinski, W.,Mazik, M.
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p. 661 - 668
(2007/10/02)
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- Electroreductive Acylation of Benzyl Chlorides with Acid Anhydrides. Stereoselective Formation of (E)-Enol Esters from Benzyl Alkyl Ketones
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Electroreduction of benzyl chlorides in the presence of acid anhydrides brought about stereoselective formation of (E)-enol esters of the corresponding benzyl alkyl ketones, the initial acylated products, in good to moderate yields.
- Nishiguchi, Ikuzo,Oki, Tsuneo,Hirashima, Tsuneaki,Shiokawa, Jiro
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p. 2005 - 2008
(2007/10/02)
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- Reactions of O,O-Diprotonated Nitro Olefins with Benzenes. Formations of Phenylacetones, 4H-1,2-Benzoxazines and Biarylacetone Oximes
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O,O-Diprotonated nitro olefins undergo three alternative electrophilic reactions which yield α-phenylacetones, 4H-1,2-benzoxazines and biphenylacetone oximes depending on the reaction conditions (temperature and time) and aromatic substrates.Although these reactions are seemingly divergent, a common intermediate of a phenylated protonated aci-nitro species, derived from the dication, is postulated to be involved in the reactions.Furthermore, the formation of benzoxazines and biphenylacetone oximes can be interpreted in terms of participation of novel chemical species with phenylethylene dication character derived from the common intermediate.
- Ohwada, Tomohiko,Okabe, Kazuaki,Ohta, Toshiharu,Shudo, Koichi
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p. 7539 - 7555
(2007/10/02)
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- Novel Electrophilic Species Equivalent to α-Keto Cations. Reactions of O,O-Diprotonated Nitro Olefins with Benzenes Yield Arylmethyl Ketones
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The N,N-dihydroxyiminium carbenium ions formed by O,O-diprotonation of nitro olefins in a strong acid, trifluoromethanesulfonic acid (TFSA), are discrete and novel dipositively charged species.The dications formed from α-substitited nitroethylenes are reactive electrophiles to give α-arylated ketones in high yields.This constitutes a versatile synthetic method for the preparation of α-arylated ketones, which are difficult to synthesize by the conventional Friedel-Crafts reactions.
- Okabe, Kazuaki,Ohwada, Tomohiko,Ohta, Toshiharu,Shudo, Koichi
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p. 733 - 734
(2007/10/02)
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- Studies on nucleophilic substitution reactions with cyclopentadienyliron complexes of some chloroarenes and nitorarenes and syntheses of substituted arenes by demetallation of the substitution products
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Nucleophilic substitution reactions with the cyclopentadienyliron (CpFe) complex of m- or p-dichlorobenzene with carbanion nucleophiles derived from ethyl acetoacetate (EAA), dibenzoylmethane (DBM) or diacetylmethane (DAM) were found to give only monosubstitution as previously observed for the CpFe complex of o-dichlorobenzene.Reaction of the CpFe complex of 2,6-dimethylchlorobenzene (XIVa) or 2,6-dimethylnitorbenzene (XIVb) with nucleophiles derived from ammonia, dimethylamine, n-butylamine, pyrrolidine, ethanol, phenol, o-thiocresol and EAA all gave SNAr products, without significant steric hindrance.However, no reaction was observed in the treatment of XIVa or XIVb with DBM, suggesting that only with a bulky nucleophile such as that derived from DBM were steric hindrance effects sufficiently large to prevent an SNAr reaction with XIVa or XIVb.Pyrolytic sublimation of the various SNAr products was found to cause decomposition in some cases, but in most instances, demetallation took place giving rise to substituted arenes.New substituted arenes prepared in this way in the present work included RC6H4CH(COC6H5)2, with R = p-CH3, o-Cl, m-Cl or p-Cl, and 2,6-(CH3)2C6H3Y, with Y = CH3(CH2)3NH, C2H5O or o-CH3C6H4S.
- Abd-El-Aziz, A.S.,Lee, C. C.,Piorko, A.,Sutherland, R. G.
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- THE NEF REACTION ON TRIALKYLSILYL NITRONATES PROMOTED BY m-CHLOROPERBENZOIC ACID, AN EFFICIENT ROUTE TO α-ALKOXYKETONES FROM NITROALKANES
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Treatment of a nitroalkene with nucleophiles, followed by silylation of the resulting nitroalkane and subsequent treatment with m-chloroperbenzoic acid provides α-functionalized carbonyl compounds in good yields.
- Aizpurus, J. M.,Oiarbide, M.,Palomo, C.
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p. 5361 - 5364
(2007/10/02)
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- HYPERVALENT IODINE AS GOOD LEAVING GROUP: OXIDATIVE REARRANGEMENT OF 1-IODO-2-METHOXY-2-ARYLALKANES.
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A new example of the good leaving group properties of hypervalent iodine is reported: oxidative rearrangement of 1-iodo-2-methoxy-2-arylalkanes 1 (R=alkyl) provides, via 1,2-aryl shift, alkyl benzyl ketones 3 in good yields.
- Citterio, Attilio,Gandolfi, Marco,Giordano, Claudio,Castaldi, Graziano
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p. 1665 - 1666
(2007/10/02)
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- Aromatic Acetonylation Promoted by Manganese(III) and Cerium(IV) Salts
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Treatment of aromatic hydrocarbons with acetone and manganese(III) acetate gave rise to arylacetones in yields ranging from 25 percent with chlorobenzene to 74 percent with anisole.Cerium(IV) salts were also successfully used as promoters but gave lower yields.The reactions were relatively free of side products except with toluene.Isomer distributions, relative rates, and partial rate factors were determined for acetonylation of anisole, toluene, chlorobenzene, and fluorobenzene.A Hammett plot of the log of the partial rate factors for the manganese(III) system vs. ?-constants gave a slope, ρ, of -2.4 +/- 0.3.An isotope effect kH/kD = 3.8 was observed for the manganese(III)-promoted reaction with acetone-d6, indicating rate-determining proton loss from acetone.The overall mechanism involves formation and attack of acetonyl radicals onto the aromatic hydrocarbon followed by subsequent oxidative deprotonation of the resulting ?-radical complex.The acetonyl radical exhibits appreciable electron-deficient character in its substitution behavior with aromatic hydrocarbons.
- Kurz, Michael E.,Baru, Vijayalakshmi,Nguyen, P-Nhi
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p. 1603 - 1607
(2007/10/02)
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- ACETONYLATION AROMATIQUE HOMOLYTIQUE
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Treatment of monosubstituted benzene derivatives with acetone and manganese(III) acetate in acetic acid gave rise to products of homolytic aromatic substitution in fairly good yields and high purity except for toluene.Isomer distribution, relative rates and partial rate factors were determeined for toluene, anisole, chlorobenzene, bromobenzene and benzonitrile.A Hammet plot of the logarithm of the partial rate factors for meta and para positions vs. ?-constants gave a slope ρ of -1.74 +/- 0.40 (confidence interval at the level 95percent).When using ?+-constants the slope becomes ρ+ = -1.25 +/- 0.36.The negative velues of ρ and ρ+ indicated that the acetonyl radical has an appreciable electrophilic character.
- Gardrat, C.
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p. 897 - 902
(2007/10/02)
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- Arylation and 1-Alkenylation on α-Position of Ketones via Tributyltin Enolates Catalyzed by Palladium Complex
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The reaction of tributyltin enolates, prepared from tributyltin methoxide and enol acetates in situ, with aryl and 1-alkenyl bromides in the presence of dichlorobis(tri-o-tolylphosphine)palladium was found to give α-aryl and α-(1-alkenyl) ketones, respectively, in good yields with essentially complete retention of the enol acetate regiochemistry.
- Kosugi, Masanori,Hagiwara, Isao,Sumiya, Takao,Migita, Toshihiko
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p. 241 - 246
(2007/10/02)
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- REDUCTIVE CONVERSION OF NITRO ALKENES TO KETONES AND/OR OXIMES IN AN AQUEOUS HClO4-CH2Cl2-DIOXANE-(Pb) SYSTEM
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Electrochemical and chemical reduction of nitro alkenes in an aqueous HClO4-CH2Cl2-dioxane-(Pb) system afforded ketones and oximes in good yields, each of which can be obtained selectively by treating with either aqueous formaldehyde or hydroxylamine as a proper workup process, respectively.
- Torii, Sigeru,Tanaka, Hideo,Katoh, Tetsuo
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p. 607 - 610
(2007/10/02)
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