- Markovnikov Wacker-Tsuji Oxidation of Allyl(hetero)arenes and Application in a One-Pot Photo-Metal-Biocatalytic Approach to Enantioenriched Amines and Alcohols
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The Wacker-Tsuji aerobic oxidation of various allyl(hetero)arenes under photocatalytic conditions to form the corresponding methyl ketones is presented. By using a palladium complex [PdCl2(MeCN)2] and the photosensitizer [Acr-Mes]ClO4 in aqueous medium and at room temperature, and by simple irradiation with blue led light, the desired carbonyl compounds were synthesized with high conversions (>80%) and excellent selectivities (>90%). The key process was the transient formation of Pd nanoparticles that can activate oxygen, thus recycling the Pd(II) species necessary in the Wacker oxidative reaction. While light irradiation was strictly mandatory, the addition of the photocatalyst improved the reaction selectivity, due to the formation of the starting allyl(hetero)arene from some of the obtained by-products, thus entering back in the Wacker-Tsuji catalytic cycle. Once optimized, the oxidation reaction was combined in a one-pot two-step sequential protocol with an enzymatic transformation. Depending on the biocatalyst employed, i. e. an amine transaminase or an alcohol dehydrogenase, the corresponding (R)- and (S)-1-arylpropan-2-amines or 1-arylpropan-2-ols, respectively, could be synthesized in most cases with high yields (>70%) and in enantiopure form. Finally, an application of this photo-metal-biocatalytic strategy has been demonstrated in order to get access in a straightforward manner to selegiline, an anti-Parkinson drug. (Figure presented.).
- Albarrán-Velo, Jesús,Gotor-Fernández, Vicente,Lavandera, Iván
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p. 4096 - 4108
(2021/08/19)
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- 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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- 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
-
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
-
supporting information
p. 526 - 538
(2020/01/08)
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- Bromomethyl Silicate: A Robust Methylene Transfer Reagent for Radical-Polar Crossover Cyclopropanation of Alkenes
-
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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- Deracemization of Racemic Amines to Enantiopure (R)- and (S)-amines by Biocatalytic Cascade Employing ω-Transaminase and Amine Dehydrogenase
-
A one-pot deracemization strategy for α-chiral amines is reported involving an enantioselective deamination to the corresponding ketone followed by a stereoselective amination by enantiocomplementary biocatalysts. Notably, this cascade employing a ω-transaminase and amine dehydrogenase enabled the access to both (R)-and (S)-amine products, just by controlling the directions of the reactions catalyzed by them. A wide range of (R)-and (S)-amines was obtained with excellent conversions (>80 %) and enantiomeric excess (>99 % ee). Finally, preparative scale syntheses led to obtain enantiopure (R)- and (S)-13 with the isolated yields of 53 and 75 %, respectively.
- Yoon, Sanghan,Patil, Mahesh D.,Sarak, Sharad,Jeon, Hyunwoo,Kim, Geon-Hee,Khobragade, Taresh P.,Sung, Sihyong,Yun, Hyungdon
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p. 1898 - 1902
(2019/02/27)
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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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- Kinetic Resolution and Deracemization of Racemic Amines Using a Reductive Aminase
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The NADP(H)-dependent reductive aminase from Aspergillus oryzae (AspRedAm) was combined with an NADPH oxidase (NOX) to develop a redox system that recycles the co-factor. The AspRedAm-NOX system was applied initially for the kinetic resolution of a variety of racemic secondary and primary amines to yield S-configured amines with enantiomeric excess (ee) values up to 99 %. The addition of ammonia borane to this system enabled the efficient deracemization of racemic amines, including the pharmaceutical drug rasagiline and the natural product salsolidine, with conversions up to >98 % and >99 % ee Furthermore, by using the AspRedAm W210A variant it was possible to generate the opposite R enantiomers with efficiency comparable to, or even better than, the wildtype AspRedAm.
- Aleku, Godwin A.,Mangas-Sanchez, Juan,Citoler, Joan,France, Scott P.,Montgomery, Sarah L.,Heath, Rachel S.,Thompson, Matthew P.,Turner, Nicholas J.
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p. 515 - 519
(2018/02/15)
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- Two-Enzyme Hydrogen-Borrowing Amination of Alcohols Enabled by a Cofactor-Switched Alcohol Dehydrogenase
-
The NADPH-dependent secondary alcohol dehydrogenase from Thermoanaerobacter ethanolicus (TeSADH), displaying broad substrate specificity and low enantioselectivity, was engineered to accept NADH as a cofactor. The engineered TeSADH showed a >10 000-fold switch from NADPH towards NADH compared to the wildtype enzyme. This TeSADH variant was applied to a biocatalytic hydrogen-borrowing system that employed catalytic amounts of NAD+, ammonia, and an amine dehydrogenase, which thereby enabled the conversion a range of alcohols into chiral amines.
- Thompson, Matthew P.,Turner, Nicholas J.
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p. 3833 - 3836
(2017/09/25)
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- Direct Alkylation of Amines with Primary and Secondary Alcohols through Biocatalytic Hydrogen Borrowing
-
The reductive aminase from Aspergillus oryzae (AspRedAm) was combined with a single alcohol dehydrogenase (either metagenomic ADH-150, an ADH from Sphingobium yanoikuyae (SyADH), or a variant of the ADH from Thermoanaerobacter ethanolicus (TeSADH W110A)) in a redox-neutral cascade for the biocatalytic alkylation of amines using primary and secondary alcohols. Aliphatic and aromatic secondary amines were obtained in up to 99 % conversion, as well as chiral amines directly from the racemic alcohol precursors in up to >97 % ee, releasing water as the only byproduct.
- Montgomery, Sarah L.,Mangas-Sanchez, Juan,Thompson, Matthew P.,Aleku, Godwin A.,Dominguez, Beatriz,Turner, Nicholas J.
-
supporting information
p. 10491 - 10494
(2017/08/22)
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- Enantioselective synthesis of β-substituted chiral allylic amines: Via Rh-catalyzed asymmetric hydrogenation
-
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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- Anti-Markovnikov Oxidation of β-Alkyl Styrenes with H2O as the Terminal Oxidant
-
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
-
supporting information
p. 12037 - 12040
(2016/09/28)
-
- Pinacolatoboron fluoride (pinBF) is an efficient fluoride transfer agent for diastereoselective synthesis of benzylic fluorides
-
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.
-
p. 3373 - 3377
(2015/06/02)
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- Palladium-Catalyzed Mono-α-arylation of Acetone at Room Temperature
-
The first examples of acetone mono-α-arylation at room temperature are described, enabled by use of a [Pd(cinnamyl)Cl]2/JosiPhos catalyst system. (Hetero)aryl chloride, bromide, and iodide electrophiles featuring or lacking ortho-substitution, and comprising a range of functionalities (e.g., alkoxy, cyano, fluoro, trifluoromethyl, or alkenyl) and heteroaryl motifs (e.g., pyrrole, pyridine, isoquinoline, quinoline, quinaldine, (benzo)thiophene, benzothiazole, or benzodioxole) were successfully accommodated. Proof-of-principle experiments confirm that other (hetero)aryl methyl ketones can also be employed in such room temperature mono-α-arylations. The established substrate scope is the most extensive reported to date for acetone mono-α-arylation under any conditions, and more generally represents the first room temperature ketone mono-α-arylations employing a structurally diverse set of (hetero)aryl chlorides. Chill out: The first examples of acetone mono-α-arylation at room temperature are described. The substrate scope is the most extensive reported to date for acetone mono-α-arylation under any conditions, and represents the first room temperature ketone mono-α-arylations employing a diverse set of (hetero)aryl chlorides.
- Macqueen, Preston M.,Chisholm, Alicia J.,Hargreaves, Breanna K. V.,Stradiotto, Mark
-
supporting information
p. 11006 - 11009
(2015/11/10)
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- Expedient Access to 2,3-Dihydropyridines from Unsaturated Oximes by Rh(III)-Catalyzed C-H Activation
-
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)
-
- A convenient catalytic oxidative 1,2-shift of arylalkenes for preparation of α-aryl ketones mediated by NaI
-
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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- 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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- Palladium(III)-catalyzed fluorination of arylboronic acid derivatives
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A practical, palladium-catalyzed synthesis of aryl fluorides from arylboronic acid derivatives is presented. The reaction is operationally simple and amenable to multigram-scale synthesis. Evaluation of the reaction mechanism suggests a single-electron-transfer pathway, involving a Pd(III) intermediate that has been isolated and characterized.
- Mazzotti, Anthony R.,Campbell, Michael G.,Tang, Pingping,Murphy, Jennifer M.,Ritter, Tobias
-
supporting information
p. 14012 - 14015
(2013/10/21)
-
- Catalytic oxidative 1,2-shift in 1,1′-disubstituted olefins using arene(iodo)sulfonic acid as the precatalyst and oxone as the oxidant
-
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.
-
supporting information
p. 1650 - 1653
(2013/06/27)
-
- β-fluoroamphetamines via the stereoselective synthesis of benzylic fluorides
-
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.
-
supporting information; experimental part
p. 2936 - 2939
(2010/09/10)
-
- Fe(II)-catalyzed amination of aromatic C-H bonds via ring opening of 2 H-azirines: Synthesis of 2,3-disubstituted indoles
-
A general method for the synthesis of 2,3-disubstituted indoles is described. The key feature of this method is the amination of aromatic C-H bonds via FeCl2-catalyzed ring opening of 2H-azirines. The method tolerates a variety of functional groups such as Br, F, NO2, OMe, CF3, OTBS, alkenes, and OPiv. The method can also be extended to synthesize azaindoles.
- Jana, Samaresh,Clements, MacK D.,Sharp, Barry K.,Zheng, Nan
-
supporting information; scheme or table
p. 3736 - 3739
(2010/11/03)
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- Copper catalyzed arylation/C-C bond activation: An approach toward α-aryl ketones
-
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)
-
- Development of a robust and practical process for the Darzens condensation and α,β-epoxide rearrangement: Scope and limitations of the methodology
-
A practical and robust process for the Darzens condensation of substituted benzaldehydes and subsequent α,β-epoxy rearrangement is reported. The process developed is both amenable to large scale and parallel synthesis. While electron-poor benzaldehydes gave mixtures of aryl ketones and 2-substituted aryl ketones in mediocre to low yields, electron-rich benzaldehydes were found to react in high yields with complete regioselectivity to form 2-substituted aryl ketones. Georg Thieme Verlag Stuttgart.
- Zimbron, Jeremy Malcolm,Seeger-Weibel, Manuela,Hirt, Hans,Gallou, Fabrice
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p. 1221 - 1226
(2008/12/22)
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- Oxidative rearrangements of arylalkenes with [hydroxy(tosyloxy)iodo]benzene in 95% methanol: A general, regiospecific synthesis of α-aryl ketones
-
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)
-
- Nickel-catalyzed direct electrochemical cross-coupling between aryl halides and activated alkyl halides
-
The electrochemical reduction of a mixture of aryl halides and activated alkyl halides in DMF in the presence of catalytic amount of NiBr2bipy leads to cross-coupling products in good to high yields. The method applies to the synthesis of α-aryl ketones, α-aryl esters, and allylated compounds from readily available organic halides. Optimization of the process has been obtained by slowly adding the most reactive organic halide (usually the activated alkyl halide) during the electrolysis which is best conducted at 70 °C when aryl bromides are involved.
- Durandetti, Muriel,Nedelec, Jean-Yves,Perichon, Jacques
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p. 1748 - 1755
(2007/10/03)
-
- A novel method of arylation of α-chloroketones
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α-Arylated ketones were obtained in moderate to good yields by one-step electroreductive coupling of α-chloroketones and arylhalides in DMF and in the presence of a Al- or Zn-sacrificial anode and a catalytic amount of a nickel complex.
- Durandetti,Sibille,Nedelec,Perichon
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p. 145 - 151
(2007/10/02)
-
- Mass spectrometric investigations on phenylacetic acid derivatives, IV: Loss of ortho-substituents from ionized phenyl-2-propanones upon electron impact
-
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)
-
- Preparation of benzyl ketones
-
Benzyl ketones of the general formula I STR1 where R1 is C1 -C8 -alkyl which is unsubstituted or substituted by cycloalkyl or aryl and R2 and R3 are each halogen, C1 -C4 -alkyl, hydroxyl, C1 -C4 -alkoxy or C2 -C4 -methylenedioxy, are prepared by a process in which a glycol monoether of the general formula II STR2 where R1, R2 and R3 have the abovementioned meanings and R4 is C1 -C8 -alkyl, is converted in the presence of silica, a phosphate or a zeolite at from 50° to 500° C. and under from 0.01 to 50 bar.
- -
-
-
- Electroreductive Acylation of Benzyl Chlorides with Acid Anhydrides. Stereoselective Formation of (E)-Enol Esters from Benzyl Alkyl Ketones
-
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)
-
- ELECTRFLUORATION EN POSITION BENZYLIQUE DANS LE SULFOLANE
-
The use of sulfolane as a solvent instead of acetonitrile in the electrofluorination of benzylic derivatives 1, (R=H, Cl) gives greater yields of benzylic fluorides 2, since the formation of acetamide byproducts 4 is prevented.However, the parallel fluorination of the aromatic nucleus is not avoided under these conditions.
- Laurent, Eliane,Marquet, Bernard,Tardivel, Robert
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p. 115 - 126
(2007/10/02)
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- HYPERVALENT IODINE AS GOOD LEAVING GROUP: OXIDATIVE REARRANGEMENT OF 1-IODO-2-METHOXY-2-ARYLALKANES.
-
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
-
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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- The Allopolarization Principle and its Applications, IV. Substituent Effects in the Methylation of Enolate Anions
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The ratio of O- and C-methylated products in the reaction of the sodium salts of acetophenones 1, propiophenones 3, phenylacetones 5, β-dicarbonyl compounds 12, α-cyanocarbonyl compounds 13, acetaldehyde, propionaldehyde, and diethylketone with dimethyl sulfate, methyl iodide, and trimethyl phosphate in HMPTA has been determined with regard to the effect of substituents.In some cases the influence of solvents, concentration and temperature has also been studied.
- Gompper, Rudolf,Vogt, Hans-Hubert
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p. 2866 - 2883
(2007/10/02)
-