- The regioisomeric triphenylaminoethanols - Comparison of their efficiency in enantioselective catalysis
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Both enantiomers of the novel amino alcohol (R)- and (S)-2 are prepared from the corresponding enantiomer of the mandelic acid-derived ethanediol 3. The regioisomeric amino alcohols 1 and 2 are converted into the imines 7 and 8, respectively. Titanium com
- Braun, Manfred,Fleischer, Ralf,Mai, Brigitte,Schneider, Marc-Andre,Lachenicht, Stefan
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- Reactions on Aromatic Olefins Induced by Aminium Salts: Protic-Acid or Radical Cation Catalyzed Processes
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Aromatic olefins by reaction with aminium salts lead, in strongly acidic reaction media, to different reaction products, arising from the intermediate formation of carbocation or radical-cation species.
- Ciminale, Francesco,Lopez, Luigi,Mele, Giuseppe
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- Solid-solid catalysis by ultrafine crystallites of heteropoly compound for pinacol rearrangement
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Cs2.5H0.5PW12O40 consisting of ultrafine crystallites efficiently catalyzes pinacol rearrangement of 1,1,2-triphenyl-1,2-ethanediol at room temperature in solid-solid reaction system, giving the corresponding al
- Toyoshi, Yasuo,Nakato, Teruyuki,Tamura, Rui,Takahashi, Hiroki,Tsue, Hirohito,Hirao, Ken-ichi,Okuhara, Toshio
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- Palladium-catalyzed multiple arylation of phenyl ketones with aryl bromides
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Benzyl phenyl ketones undergo triarylation upon treatment with excess aryl bromides in the presence of a catalytic amount of Pd(PPh3)4 and Cs2CO3 as base in o-xylene on the α- and two ortho-positions of the carb
- Satoh, Tetsuya,Kametani, Yoko,Terao, Yoshito,Miura, Masahiro,Nomura, Masakatsu
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- Aminium hexachloroantimonate salts as latent sources of antimony pentachloride in pinacolic rearrangement of vicinal diols
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Rearrangements of various vicinal diols (1a-f) induced by hexachloroantimonate aminium salts A or B were found to occur in a similar manner when antimony pentachloride was used instead of aminium salts. Antimony pentachloride is proposed as the active catalytic species, possibly deriving from the oxidation of the hexachloroantimonate anion Sbcl6 - by the aminium counterpart. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
- Ciminale, Francesco,Lopez, Luigi,Nacci, Angelo,D'Accolti, Lucia,Vitale, Floriana
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- The acid dissociation constant of triphenylethenethiol, a simple thioenol, and that of its oxygen-enol analog
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The acidity constant, pQ(a)(E) = 8.49, for the stable thioenol, triphenylethenethiol, was determined by spectrophotometric titration, and that, pQ(a)(E) = 11.37, for its unstable oxygen analog, triphenylethenol, was determined by analysis of its ketonizat
- Chiang, Yvonne,Kresge, A. Jerry,Schepp, Norman P.,Popik, Vladimir V.,Rappoport, Zvi,Selzer, Tzvia
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- Palladium-catalyzed arylation of ketone enolates: an expeditious entry to tamoxifen-related 1,2,2-triarylethanones.
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[reaction: see text]. After a rigorous study on the effect of several catalytic systems, a simple, high yielding procedure for the preparation of 1,2,2-triarylethanones, skeletal analogues of tamoxifen, is presented. Apart from the economic and environmen
- Churruca, Fatima,SanMartin, Raul,Tellitu, Imanol,Dominguez, Esther
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- Chemoselectivity of Pinacol Rearrangement Originate by Different Hexafluoroantimonate Oxidant
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Using 1,1,2-triphenylethane-1,2-diol, AgSbF6, and NOSbF6, two different carbonyl products of rearrangement were synthesized: neutral ketone compound 1,2,2-triphenylethanone (1) from NOSbF6 and coordination complex of Ag io
- Chen, Xiaoyu,Wu, Chunlei,Li, Jia,Li, Yue
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- Benzylic Aroylation of Toluenes Mediated by a LiN(SiMe3)2/Cs+System
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Chemoselective deprotonative functionalization of benzylic C-H bonds is challenging, because the arene ring contains multiple aromatic C(sp2)-H bonds, which can be competitively deprotonated and lead to selectivity issues. Recently it was found that bimetallic [MN(SiMe3)2 M = Li, Na]/Cs+ combinations exhibit excellent benzylic selectivity. Herein, is reported the first deprotonative addition of toluenes to Weinreb amides mediated by LiN(SiMe3)2/CsF for the synthesis of a diverse array of 2-arylacetophenones. Surprisingly, simple methyl benzoates also react with toluenes under similar conditions to form 2-arylacetophenones without double addition to give tertiary alcohol products. This finding greatly increases the practicality and impact of this chemistry. Some challenging substrates with respect to benzylic deprotonations, such as fluoro and methoxy substituted toluenes, are selectively transformed to 2-aryl acetophenones. The value of benzylic deprotonation of 3-fluorotoluene is demonstrated by the synthesis of a key intermediate in the preparation of Polmacoxib.
- Gu, Yuanyun,Zhang, Zhen,Wang, Yan-En,Dai, Ziteng,Yuan, Yaqi,Xiong, Dan,Li, Jie,Walsh, Patrick J.,Mao, Jianyou
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supporting information
p. 406 - 418
(2022/01/14)
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- Palladium-catalyzed synthesis of α-aryl acetophenones from styryl ethers and aryl diazonium saltsviaregioselective Heck arylation at room temperature
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Preparation of α-aryl acetophenones from styryl ethers and aryldiazonium salts is described. The reaction is catalyzed by palladium acetate at room temperature in the absence of ligand and base. The developed method is highly attractive in terms of reaction conditions, substrate scope, functional group tolerance and yields. Synthetic applications of the present method are demonstrated by preparing α-aryl indoles and 3-aryl isocoumarin from styryl ethers.
- Venkatesh, Rapelly,Singh, Adesh Kumar,Lee, Yong Rok,Kandasamy, Jeyakumar
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p. 7832 - 7837
(2021/09/28)
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- Strongly Entangled Triplet Acyl-Alkyl Radical Pairs in Crystals of Photostable Diphenylmethyl Adamantyl Ketones
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Radical pairs generated in crystalline solids by bond cleavage reactions of triplet ketones offer the unique opportunity to explore a frontier of spin dynamics where rigid radicals are highly entangled as the result of short inter-radical distances, large
- Garcia-Garibay, Miguel A.,Hipwell, Vince M.,Park, Jin H.,Rivera, Edris A.
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p. 8886 - 8892
(2021/06/28)
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- Palladium-catalyzed denitrative α-arylation of ketones with nitroarenes
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The palladium-catalyzed α-arylation of ketones with readily available nitroarenes and nitroheteroarenes provides access to useful α-aryl and α-heteroaryl ketones. The use of the Pd/ BrettPhos catalysts was critical to achieve high efficiency for these transformations, whereas other catalysts led to decreased yields or no conversions. The intramolecular type substrate was also applied in this methodology and gave a chromone derivative. Polyaromatic carbonyl compounds can be easily obtained by multicomponent tandem reactions, via nucleophilic aromatic substitution (SNAr) or cross-coupling reaction followed by this denitrative arylation. Kinetic experiments show that the electronic effect of nitrobenzenes has a greater effect on the reaction rate than the electronic effect of ketones.
- Li, Zhirong,Peng, Yonggang,Wu, Tao
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supporting information
(2021/02/16)
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- Method for preparing alpha-aryl ketone compound by using palladium complex
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The invention relates to a method for preparing an alpha-aryl ketone compound by using a palladium complex, which comprises the steps of in the presence of alkali, taking ketone and halogenated hydrocarbon as raw materials, taking the palladium complex containing an ortho-carborane benzothiazole structure as a catalyst, and carrying out alpha-halogenation reaction at room temperature to prepare the alpha-aryl ketone compound. Compared with the prior art, the palladium complex containing the ortho-carborane benzothiazole structure is applied to catalysis of the alpha-halogenation reaction of ketone and halogenated hydrocarbon, the alpha-aryl substituted ketone compound is prepared through a one-pot method, synthesis of the alpha-aryl ketone compound at room temperature by using simple, easily available and cheap raw materials is achieved, and the method has the advantages of low catalyst use equivalent, mild reaction conditions, more catalytic substrates, high substrate universality and high yield.
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Paragraph 0028; 0034-0037
(2021/07/17)
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- Metal Free, Direct and Selective Deoxygenation of α-Hydroxy Carbonyl Compounds: Access to α,α-Diaryl Carbonyl Compounds
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An efficient, metal free, direct and selective deoxygenation of α-hydroxy carbonyl compounds is achieved with the aid of catalytic amount of aqueous HClO4 (70 %) and triethylsilane as hydride source. A variety of α-hydroxy-α,α-diaryl carbonyl compounds are selectively deoxygenated to give α,α-diaryl carbonyl compounds in good to excellent yields. Intermediacy of α-keto carbenium ion is proposed on the basis of some control experiments and atmospheric pressure chemical ionization mass spectral analysis.
- Kumar, Anil,Sandeep,Venugopalan, Paloth
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- Transition Metal-Free Aroylation of Diarylmethanes with N-Bn-N-Boc Arylamides and N-Acylpyrroles
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In the last 20 years, efficient transition metal catalysts for the α-arylation of enolates have been introduced. Despite the popularity and utility of these reactions, there remains room for improvement (reduced costs, elimination of transition metals and specialized ligands). Herein is reported a general, scalable and green method for aroylation of simple diarylmethane pronucleophiles through direct acyl C?N cleavage of N-Bn?N-Boc arylamides and N-acylpyrroles under transition metal-free conditions. Importantly, a 1 : 1 ratio of the amide to the pronucleophile is employed. Unlike use of Weinreb amides, this method avoids preformed organometallics (organolithium and Grignard reagents) and does not employ cryogenic temperatures, which are difficult and costly to achieve on scale. The operationally simple protocol provides straightforward access to a variety of sterically and electronically diverse 1,2,2-triarylethanones, a group of compounds with high-value in medicinal chemistry. (Figure presented.).
- Yang, Fan,Zou, Dong,Chen, Shuguang,Wang, Huan,Zhao, Yichen,Zhao, Liyi,Li, Linlin,Li, Jie,Walsh, Patrick J.
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supporting information
p. 3423 - 3430
(2020/07/27)
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- Combined Photoredox and Carbene Catalysis for the Synthesis of Ketones from Carboxylic Acids
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As a key element in the construction of complex organic scaffolds, the formation of C?C bonds remains a challenge in the field of synthetic organic chemistry. Recent advancements in single-electron chemistry have enabled new methods for the formation of various C?C bonds. Disclosed herein is the development of a novel single-electron reduction of acyl azoliums for the formation of ketones from carboxylic acids. Facile construction of the acyl azolium in situ followed by a radical–radical coupling was made possible merging N-heterocyclic carbene (NHC) and photoredox catalysis. The utility of this protocol in synthesis was showcased in the late-stage functionalization of a variety of pharmaceutical compounds. Preliminary investigations using chiral NHCs demonstrate that enantioselectivity can be achieved, showcasing the advantages of this protocol over alternative methodologies.
- Betori, Rick C.,Davies, Anna V.,Fitzpatrick, Keegan P.,Scheidt, Karl A.
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p. 9143 - 9148
(2020/03/30)
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- Arylation of Aldehydes to Directly Form Ketones via Tandem Nickel Catalysis
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A nickel-catalyzed arylation of both aliphatic and aromatic aldehydes proceeds with air-stable (hetero)arylboronic acids, with an exceptionally wide substrate scope. The neutral condition tolerates acidic hydrogen and sensitive polar groups and also preserves α-stereocenters of some chiral aldehydes. Interestingly, this nickel(0) catalysis does not follow common 1,2-insertion of arylmetal species to aldehydes and β-hydrogen elimination.
- Lei, Chuanhu,Zhu, Daoyong,Tangcueco, Vicente Iii Tiu,Zhou, Jianrong Steve
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supporting information
p. 5817 - 5822
(2019/08/26)
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- Aqueous α-Arylation of Mono- and Diarylethanone Enolates at Low Catalyst Loading
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Acetophenone and deoxybenzoin derivatives are selectively α-arylated using a combination of very small amounts of palladium acetate and diphenylphosphine oxide as catalyst system and water as the only solvent. Target di- and triarylethanones are isolated virtually free of metal residues, and the reaction is amenable to gram-scale. A mechanistic proposal based on TEM images, poisoning experiments, kinetic plot and ESI-MS spectrometry is also provided. (Figure presented.).
- Astarloa, Iratxe,SanMartin, Raul,Herrero, María Teresa,Domínguez, Esther
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supporting information
p. 1711 - 1718
(2018/03/21)
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- Iron(III) nitrate-induced aerobic and catalytic oxidative cleavage of olefins
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Microwave-assisted catalytic oxidative cleavage of olefins using Fe(NO3)3·9H2O under O2 is reported. This reaction system is particularly effective when 9-benzylidene-9H-fluorene derivatives are used as substrates even though they are tri- and tetra-substituted olefins.
- Amaya, Toru,Fujimoto, Hayato
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supporting information
p. 2657 - 2660
(2018/06/04)
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- Pinacol Rearrangement and Direct Nucleophilic Substitution of Allylic Alcohols Promoted by Graphene Oxide and Graphene Oxide CO2H
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Graphene oxide (GO) and carboxylic acid functionalized GO (GO–CO2H) have been found to efficiently promote the heterogeneous and environmentally friendly pinacol rearrangement of 1,2-diols and the direct nucleophilic substitution of allylic alcohols. In general, high yields and regioselectivities are obtained in both reactions using 20 wt % of catalyst loading and mild reaction conditions.
- Gómez-Martínez, Melania,Baeza, Alejandro,Alonso, Diego A.
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p. 1032 - 1039
(2017/03/27)
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- Photosensitizer-Free Visible-Light-Mediated Gold-Catalyzed 1,2-Difunctionalization of Alkynes
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Under visible-light irradiation, the gold-catalyzed intermolecular difunctionalization of alkynes with aryl diazonium salts in methanol affords a variety of α-aryl ketones in moderate to good yields. In contrast to previous reports on gold-catalyzed reactions that involve redox cycles, no external oxidants or photosensitizers are required. The reaction proceeds smoothly under mild reaction conditions and shows broad functional-group tolerance. Further applications of this method demonstrate the general applicability of the arylation of a vinyl gold intermediate instead of the commonly used protodemetalation step. This step provides facile access to functionalized products in one-pot processes. With a P,N-bidentate ligand, a stable aryl gold(III) species was obtained, which constitutes the first direct experimental evidence for the commonly postulated direct oxidative addition of an aryl diazonium salt to a pyridine phosphine gold(I) complex.
- Huang, Long,Rudolph, Matthias,Rominger, Frank,Hashmi, A. Stephen K.
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supporting information
p. 4808 - 4813
(2016/04/19)
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- Synthesis of 2-Benzylphenyl Ketones by Aryne Insertion into Unactivated C-C Bonds
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A transition-metal-free procedure to access to functionalized 2-benzylphenyl ketones is described by direct insertion of arynes into benzylic C-C bonds. This reaction was promoted by cesium fluoride at room temperature, allowing the products to form in high selectivity and achieve good functional group tolerance.
- Rao, Bin,Tang, Jinghua,Zeng, Xiaoming
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supporting information
p. 1678 - 1681
(2016/04/26)
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- Iron-Catalyzed α-Arylation of Deoxybenzoins with Arenes through an Oxidative Dehydrogenative Approach
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A novel α-arylation of deoxybenzoins with non-prefunctionalized arenes is developed through an iron-catalyzed oxidative dehydrogenative approach. The reaction shows broad substrate scope and functional group tolerance and thus provides efficient access to synthetically useful 1,2,2-triarylethanones. A reasonable mechanism is also proposed.
- Chen, Tao,Li, Yi-Fan,An, Yang,Zhang, Fu-Min
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supporting information
p. 4754 - 4757
(2016/09/28)
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- LIGAND, NICKEL COMPLEX COMPRISING LIGAND, AND REACTION USING NICKEL COMPLEX
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PROBLEM TO BE SOLVED: To provide a method for directly carrying out arylation, especially α-arylation, of a carbonyl compound or a thiocarbonyl compound by using a more inexpensive phenol derivative and a nickel catalyst, and to provide a novel nickel cat
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Paragraph 0282; 0284; 0285
(2016/10/07)
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- Transition-Metal-Free α-Arylation of Enolizable Aryl Ketones and Mechanistic Evidence for a Radical Process
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The α-arylation of enolizable aryl ketones can be carried out with aryl halides under transition-metal-free conditions using KOtBu in DMF. The α-aryl ketones thus obtained can be used for step- and cost-economic syntheses of fused heterocycles and Tamoxifen. Mechanistic studies demonstrate the synergetic role of base and solvent for the initiation of the radical process.
- Pichette Drapeau, Martin,Fabre, Indira,Grimaud, Laurence,Ciofini, Ilaria,Ollevier, Thierry,Taillefer, Marc
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supporting information
p. 10587 - 10591
(2015/09/02)
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- Palladium catalyzed addition of arylboronic acid or indole to nitriles: Synthesis of aryl ketones
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Aryl ketones can be synthesized conveniently by a palladium catalyzed addition of arylboronic acid to nitriles in aqueous triflic acid. This catalytic system was extended to the addition of unprotected indoles to nitriles under a slightly modified condition to produce 3-acyl indoles in good yields.
- Das, Tuluma,Chakraborty, Amarnath,Sarkar, Amitabha
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supporting information
p. 7198 - 7202
(2015/01/09)
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- Nickel-catalyzed α-arylation of ketones with phenol derivatives
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The nickel-catalyzed α-arylation of ketones with readily available phenol derivatives (esters and carbamates) provides access to useful α-arylketones. For this transformation, 3,4-bis(dicyclohexylphosphino) thiophene (dcypt) was identified as a new, enabling, air-stable ligand for this transformation. The intermediate of an assumed C-O oxidative addition was isolated and characterized by X-ray crystal-structure analysis. The nickel-catalyzed α-arylation of ketones with readily available phenol derivatives (esters and carbamates) provides access to useful α-arylketones. The use of 3,4-bis(dicyclohexylphosphino)thiophene (dcypt) as an air-stable ligand enables this transformation. The intermediate of an assumed C-O oxidative addition was isolated and characterized by X-ray crystal-structure analysis.
- Takise, Ryosuke,Muto, Kei,Yamaguchi, Junichiro,Itami, Kenichiro
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supporting information
p. 6791 - 6794
(2014/07/08)
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- A one-pot cross-pinacol coupling/rearrangement procedure
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A new catalytic retro-pinacol/cross-pinacol reaction, followed by subsequent rearrangement or deoxygenation of the intermediately formed vicinal diols, is described. This operationally simple one-pot protocol allows isolation of geminal α,α-diphenyl ketones or 1,1-diphenyl alkenes with high yields and selectivities. Copyright
- Scheffler, Ulf,Mahrwald, Rainer
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p. 1970 - 1975,6
(2012/12/12)
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- Palladium-catalyzed α-ketone arylation under mild conditions
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The α-arylation of ketones with aryl halides catalyzed by the easily prepared and air-stable palladium complex (SIPr)Pd(Py)Cl2 (3) is described. Complex 3 displays high activity for a variety of aryl halides (activated, unactivated, and sterically hindered aryl halides) under mild conditions. Moreover, both aryl and alkyl ketones can be arylated. The α-arylation of some alkyl ketones can even be run at room temperature. The mono- or diarylated products of the unhindered dialkyl ketone 3-pentanone could be controlled by temperature and the ratio of ketones to aryl halides. Palladium-catalyzed α-ketone arylation of aryl and alkyl ketones with aryl halides is described. A total of 31 examples is presented with yields ranging from 45 to 95%.The mono- or diarylated product of the unhindered dialkyl ketone 3-pentanone could be controlled. Copyright
- Cao, Changsheng,Wang, Lingling,Cai, Zhengyuan,Zhang, Lingqiao,Guo, Jin,Pang, Guangsheng,Shi, Yanhui
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supporting information; experimental part
p. 1570 - 1574
(2011/04/17)
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- Rapid and efficient protic ionic liquid-mediated pinacol rearrangements under microwave irradiation
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Several protic ionic liquids were tested as potential mediators for pinacol rearrangements employing microwave irradiation. Using hydrobenzoin as a model substrate, the optimal conditions were found to be heating at 80°C for 5 min using H2SO4:triethylamine as the ionic liquid. A key feature of this reaction was to keep the microwave power low (20 W) to avoid ionic liquid degradation. Application of these conditions to triphenylethylene glycol gave rearrangement products in high yield and purity, while phenylethylene glycol and styrene oxide gave pinacol products that underwent a cascade aldol condensation. These conditions represent an efficient means by which pinacol rearrangements can be carried out while avoiding the use of strong Bronsted acids, high temperatures and extended reaction times. The Royal Society of Chemistry.
- Henderson, Luke C.,Byrne, Nolene
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supporting information; experimental part
p. 813 - 816
(2011/06/20)
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- Highly selective palladium-catalyzed direct c-h α-monoarylation of carbonyl compounds using water containing the surfactant polyoxyethylene- α-tocopheryl sebacate (PTS) as a solvent
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Highly selective direct C-H α-monoarylation reactions of 4-chromanones, ketones and 2-phenylacetaldehyde with aryl halides have been performed in satisfactory yields by using a tris(dibenzylideneacetone) dipalladium(0)/tri-tert-butylphosphine tetrafluoroborate catalyst system, potassium bicarbonate as the base and a solvent consisting of pure water containing a small amount of polyoxyethylene-α-tocopheryl sebacate (PTS). Analogous reaction conditions have been employed in a tandem process leading to phenyl-substituted isocoumarins from carbonyl compounds and methyl 2-bromobenzoate.
- Lessi, Marco,Masini, Tiziana,Nucara, Luca,Bellina, Fabio,Rossi, Renzo
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supporting information; experimental part
p. 501 - 507
(2011/04/15)
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- N-heterocyclic carbene-catalyzed cross-coupling of aromatic aldehydes with activated alkyl halides
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N-Heterocyclic carbene-catalyzed umpolung of aldehydes followed by their interception with diarylbromomethanes has been reported. This conceptually novel transition-metal-free cross-coupling of aldehydes with alkyl halides works well at low catalyst loadings and under mild reaction conditions leading to the formation of diaryl acetophenone derivatives in good yields. In addition, α-halo ketones and esters can also be used as aldehyde reaction partners.
- Padmanaban, Mohan,Biju, Akkattu T.,Glorius, Frank
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supporting information; experimental part
p. 98 - 101
(2011/03/19)
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- Friedel-Crafts alkylation of benzene with 1,2-diphenyl-2-propanol, 1-chloro-2,3-diphenylpropane and 2-methyl-1-phenyl-2-butanol
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The alkylation of benzene with 1,2-diphenyl-2-propanol (1) using AlCl 3/CH3NO2 catalyst gave a mixture of 1,2,2- (4) and 1,1,2-triphenylpropane (5) as product alkylates. With 85% H 2SO4 catalyst, the product consisted of E-1,2-diphenylpropene (6) after 2 h of a mixture of 5 and 6 after 18 h. Similar alkylation of benzene with 1-chloro-2,3-diphenylpropane (2) using AlCl 3 catalyst gave a mixture consisting of 4, 5 and 6. Finally, alkylation of benzene with 2-methyl-1-phenyl-2-butanol (3) using AlCl 3/CH3NO2 gave 2-methyl-1,1-diphenylbutane (10) as sole product alkylate. The identities of the products were confirmed spectroscopically and by comparison with unequivocally prepared samples. Mechanisms are proposed to rationalise the observed results.
- Khalaf, Ali A.,Awad, Ibrahim M.,El-Emary,El-Aal, H.A.K. Abd
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experimental part
p. 595 - 600
(2011/08/21)
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- Palladium-catalyzed synthesis of diarylmethanes: Exploitation of carbanionic leaving groups
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A novel route to the synthesis of diarylmethanes via a Pd-catalyzed α-arylation of benzyl ketones is rseported. By harnessing the inherent reactivity of enolates, it is possible to circumvent the need for a transmetalating reagent such as boron for the co
- Schmink, Jason R.,Leadbeater, Nicholas E.
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scheme or table
p. 2575 - 2578
(2009/10/02)
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- Reductive cross-coupling between N-acylbenzimidazoles and diarylketones promoted by Sm/TiCl4
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The reductive cross-coupling reaction between N-acylbenzimidazoles and diarylketones promoted by Sm/TiCl4 was performed in refluxing THF under a nitrogen atmosphere, to give 1,2,2-triaryl ethanones in moderate to good yields.
- Du, Jingxing,Wang, Xiaoxia,Zheng, Renwei
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- Reaction of (2-ethyl-aziridin-2-yl)diphenyl methanol and diphenyl-(2-phenyl-aziridin-2-yl)methanol with phenyl and t-butyl isocyanates, phenyl isothiocyanate and thiophosgene
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The reactions of aziridine alcohols with organic isocyanates, isothiocyanates and thiophosgene were described. It was found that the reactions with phenyl or t-butyl isocyanate give urea derivatives as major products, whereas the reaction with thiophosgene resulted in the formation of isothiocyanates derivatives. The mechanism of these reactions was proposed.
- Kryczka,Lesniak,Pasternak,Porwanski
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p. 1927 - 1934
(2008/09/18)
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- PCP-Bis(phosphinite) pincer complexes: new homogeneous catalysts for α-arylation of ketones
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Two new p-alkoxycarbonylated palladium bis(phosphinite) PCP pincer complexes are easily prepared and for the first time evaluated as homogeneous catalysts in α-arylation of ketone enolates. Apart from the total absence of phenyl-aryl exchange by-products and significantly low catalyst loadings, the general α-arylation protocols described in this letter feature not only a broad applicability to a range of ketones and aryl bromides with marked electronic and steric differences but also the possibility to generate mono-diarylated products.
- Churruca, Fátima,SanMartin, Raul,Tellitu, Imanol,Domínguez, Esther
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p. 3233 - 3237
(2007/10/03)
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- Towards a facile synthesis of triarylethanones: Palladium-catalyzed arylation of ketone enolates under homogeneous and heterogeneous conditions
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The palladium-catalyzed regioselective α-monoarylation of deoxybenzoins and α,α-diarylation of acetophenones provides general, efficient access to 1,2,2-triarylethanones. After a comprehensive search for suitable experimental conditions to optimize such transformations, both reactions are alternatively conducted by means of either commercially available polymer-anchored catalysts or a very simple homogeneous catalytic system, thus avoiding the use of complex ligands. In addition, the synthesis of deoxybenzoins employing polymer-supported fibrous palladium catalysts is reported for the first time, and the excellent catalyst recycling properties suggest applicability to industrial purposes.
- Churruca, Fátima,SanMartin, Raul,Carril, Mónica,Tellitu, Imanol,Domínguez, Esther
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p. 2393 - 2408
(2007/10/03)
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- Low-valent titanium promoted self-coupling of N-acylbenzotriazoles and their cross-coupling with diarylketones
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The self-coupling reaction of N-acylbenzotriazoles and their cross-coupling with diarylketones promoted by Sm/TiCl4 system were investigated. Self-coupling reaction could afford α-diketones or benzoins in moderate yields, while the cross-coupli
- Wang, Xiaoxia,Zhang, Yongmin
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p. 2627 - 2634
(2007/10/03)
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- Regioselective diarylation of ketone enolates by homogeneous and heterogeneous catalysis: Synthesis of triarylethanones
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A novel, one-step approach to 1,2,2-triarylethanones is achieved by an efficient palladium-catalyzed α,α-diarylation of commercially available acetophenones. After assaying an array of experimental conditions, two convenient procedures, which avoid ortho-arylation side reactions, are chosen to perform the target regioselective diarylation. The former protocol is based on the use of such a simple homogeneous system as Pd(OAc)2/PPh3/Cs2CO3, and the latter one employs a commercially available polymer-anchored catalyst, FibreCat 1026.
- Churruca, Fátima,SanMartin, Raul,Tellitu, Imanol,Domínguez, Esther
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p. 5925 - 5929
(2007/10/03)
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- Progress in the Palladium-Catalyzed α-Arylation of Ketones with Chloroarenes
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Non- and deactivated chloroarenes can be coupled with a wide range of ketones to yield the corresponding arylmethyl ketones in good to excellent yields using a palladium(II) acetate/n-BuPAd2 catalyst system. Depending on the ketone, the chloroarene/ketone ratio and the base, mono or diarylation can be effected selectively.
- Ehrentraut, Andreas,Zapf, Alexander,Beller, Matthias
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p. 209 - 217
(2007/10/03)
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- Reactions of o-iodohalobenzenes with carbanions of aromatic ketones. Synthesis of 1-aryl-2-(o-halophenyl)ethanones
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o-Iodohalobenzenes (X = I, Br, Cl) react in DMSO with the enolate ions of acetophenone, propiophenone and 1-(2-naphthyl)ethanone to afford mainly monosubstitution with retention of one halogen. The monosubstituted dehalogenated compounds are formed in low overall yields in the reactions of o-diiodobenzene with the carbanions of 1-(2-naphthyl)ethanone and of acetophenone and in the reaction of o-bromoiodobenzene with the carbanion of propiophenone. The reactions can be performed in the dark, with usually increased yields of substitution under irradiation, as well as under FeBr2 initiation. Treatment of 2-(2-bromophenyl)-1-phenylethanone with Cu bronze affords the ring closure benzofuran product. The degree of dehalogenation is discussed in terms of the energetics of the intramolecular electron transfer (ET) from the ArCO-π system to the C-halogen σ bond in the monosubstituted radical anions proposed as intermediates. The lack of ring closure of the radicals formed by dehalogenation of these radical anions is analyzed in terms of geometric factors.
- Baumgartner, Maria T.,Jimenez, Liliana B.,Pierini, Adriana B.,Rossi, Roberto A.
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p. 1092 - 1097
(2007/10/03)
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- Highly regioselective, sequential, and multiple palladium-catalyzed arylations of vinyl ethers carrying a coordinating auxiliary: An example of a heck triarylation process
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This article describes the development of new auxiliary-accelerated Heck multiarylations by intramolecular presentation of the oxidative addition complex. The introduction of a specific, palladium-coordinating dimethylamino group allows for the desired chelation-accelerated and chelation-controlled tri- and diarylation reactions. We report (a) the first example of a Heck triarylation process, (b) highly selective palladium-catalyzed diarylations of alkyl vinyl ethers, and (c) a very rapid two-phase protocol for the microwave-assisted hydrolysis of amino-substituted, arylated vinyl ethers constituting an entry to diarylated ethanals and substituted desoxybenzoins. X-ray structures and product patterns support the suggested substrate-controlled Heck reaction pathway. The catalyst-directing alkyl dimethylamino functionality was rapidly (1-2 min) and efficiently released by microwave hydrolysis after Heck multiarylation reactions. The liberated aromatic carbonyl compounds were thereafter isolated and fully characterized.
- Nilsson,Larhed,Hallberg
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p. 8217 - 8225
(2007/10/03)
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- Facile and fast pinacol rearrangement by AlCl3 in the solid state
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A facile and efficient synthetic procedure for effecting the pinacol rearrangement catalyzed by AlCl3 in the absence of solvent is developed. The rearrangement product is obtained at room temperature in a few minutes and in almost quantitative yield. Benzylic pinacols rearrange under these conditions, while aliphatic pinacols do not react.
- Rashidi-Ranjbar, Parviz,Kianmehr, Ebrahim
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p. 442 - 447
(2007/10/03)
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- Intermolecular and intramolecular ketone-nitrile reductive coupling reactions promoted by TiCl4-Sm system
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The intermolecular and intramolecular reductive coupling reactions of ketones with nitriles have been successfully promoted by low-valent titanium prepared by the TiCL4-Sm system. Substituted ketones, monocyclic α-amino alcohols and monocyclic amines composed of a number of substitution patterns have been prepared in good yields at room or THF reflux temperature under neutral conditions. The procedure can avoid over reduction of the resulting of ketones, α-amino alcohols or amines. The crystal structures of two monocyclic α-amino alcohols are reported. (C) 2000 Elsevier Science Ltd.
- Zhou, Longhu,Zhang, Yongmin
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p. 2953 - 2960
(2007/10/03)
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- Competition of mechanisms in the photochemical cleavage of the C-X bond of aryl-substituted vinyl halides
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The photolysis of aryl halides caused homolysis of the carbon-halogen bond and formation of aryl radicals. In contrast, photolysis of vinyl halides can induce both heterolysis of the C-X bond, thereby generating vinyl cations, and homolysis, giving vinyl radicals. Examples of this competition among pathways is reported here for three vinylic precursors, namely, 1,2,2- triphenylbromoethene (1), 1-phenyl-2,2-bis(o-methoxyphenyl)-1-bromoethene (11), and β-bromostyrene (19). Incursion of the photoinduced S(RN)1 process, through the intermediacy of the vinyl radical, is verified in the presence of reducing nucleophiles, such as the enolate ions of ketones, and in part with (EtO)2PO-. Conversely, incursion of the heterolytic path, and intermediacy of the vinyl cation, occurs in the presence of weak electron-donor anions, such as NO2-, N3-, and Cl-. The vinyl cation produced from 19, which is less stable than those derived from 1 and 11, gives phenylacetylene via an E1-type elimination. An estimate is provided for the intramolecular rate of interception of the vinyl cation derived from 11 by the ortho-methoxy groups of the β-o-anisyl substituents. Finally, evidence against a photoinduced electron transfer from RO- ions to vinyl halide 1 is presented.
- Galli, Carlo,Gentili, Patrizia,Guarnieri, Alessandra,Kobayashi, Shinjiro,Rappoport, Zvi
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p. 9292 - 9299
(2007/10/03)
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- Solid-solid catalysis by inorganic solid acids: Pinacol rearrangement over a heteropoly compound consisting of fine particles
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Solid-state pinacol rearrangement of 1,1,2-triphenyl-1,2-ethanediol was performed over various solid acids at room temperature. The reaction was initiated by grinding a mixture of the solid reactant and catalyst for 5 min at room temperature. Heteropoly compounds (Cs2.5 H0.5)PW12O40 and H3PW12O40) and polymer resins (Amberlyst-15 and Nation/SiO2), all which possess strong acidities, were active, whereas H-ZSM-5, SiO2-Al2O3, and p-toluenesulfonic acid were inactive. Cs2.5H0.5PW12O40 showed the highest activity (per unit catalyst weight). The turnover number, which is defined as the number of molecules reacted divided by the number of protons on the surface, exceeded 20 for 9 h, indicating that the solid-solid reaction proceeded catalytically. This activity of Cs2.5H0.5PW12O40 was higher than that for the solid-liquid reaction carried out in chloroform at room temperature, demonstrating the superiority of the solid-solid catalysis. Powder X-ray diffraction measurements indicated that [he reactant crystals became nearly amorphous by grinding with Cs2.5H0.5PW12O40, while the crystallinity of Cs2.5H0.5PW12O40 was unchanged. The microstructure built up from fine particles of Cs2.5H.05PW12 O40 would be favorable to intimate contact of the reactant with the catalyst.
- Toyoshi, Yasuo,Nakato, Teruyuki,Okuhara, Toshio
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p. 2817 - 2824
(2007/10/03)
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- Regioselective Arylation Reactions of Biphenyl-2-ols, Naphthols, and Benzylic Compounds with Aryl Halides under Palladium Catalysis
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Biphenyl-2-ols undergo regioselective mono- and diarylation upon a treatment with aryl iodides in the presence of a palladium catalyst in DMF using Cs2CO3 as a base to produce 1,1′ : 2′,1″-terphenyl-2-ol and 2′,6′-diphenylbiphenyl-2-ol and their derivatives. The reaction of 1-naphthol selectively occurs at its 8-position to give 8-aryl-1-naphthols. In the reaction of 2-naphthol with aryl bromides, diarylated compounds, 1-(2-arylphenyl)-2-naphthols, are formed as the single major products. Under similar conditions, benzyl ketones, phenylacetonitrile, and methyl phenylacetate are arylated at their benzylic position.
- Satoh, Tetsuya,Inoh, Jun-Ichi,Kawamura, Yoshiki,Kawamura, Yuichiro,Miura, Masahiro,Nomura, Masakatsu
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p. 2239 - 2246
(2007/10/03)
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- Oxidative nucleophilic substitution of hydrogen in nitroarenes with phenylacetonitrile derivatives
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Tertiary carbanions generated from α-substituted phenylacetonitriles in liquid ammonia add to nitrobenzenes in the para position to form the corresponding σ(H)-adducts which are transformed, depending on the starting nitriles and the reaction conditions, to products of oxidative nucleophilic substitution of hydrogen, ONSH or vicarious nucleophilic substitution, VNS.
- Makosza, Mieczyslaw,Stalinski, Krzysztof
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p. 8797 - 8810
(2007/10/03)
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- Solid-state organic reactions proceeding by pulverization: Oxidation and halogenation with iodosobenzene and inorganic solid-supports
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Pulverization-activation method was employed to accelerate solid-state organic reactions. Crushing and grinding of solid mixtures of hydrogen halide-treated silica gels, iodosobenzene and organic substrates in the absence of a solvent brought about smooth and rapid reactions to give halogenated and/or oxidized products in good yields. Various sulfides were smoothly converted to sulfonyl chlorides in one step in excellent yields. The surface of silica gel activated by pulverization serves as a reaction field on which reagent molecules can effectively encounter with each other.
- Sohmiya, Hajime,Kimura, Takahide,Fujita, Mitsue,Ando, Takashi
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p. 13737 - 13750
(2007/10/03)
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