- Electrochemical reactivity of S-phenacyl-O-ethyl-xanthates in hydroalcoholic (MeOH/H2O 4:1) and anhydrous acetonitrile media
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The electrochemical behavior of a series of S-phenacyl-O-ethyl-xanthates (O-ethyl-dithiocarbonate acetophenone derivatives) in hydroalcoholic (MeOH/H2O 4:1) and anhydrous media (ACN/TBAPF6) using carbon electrodes was studied. Cyclic voltammetry showed in hydroalcoholic media only two cathodic waves, whereas in ACN one anodic and two cathodic waves were present. The first cathodic wave corresponded to the reduction of the phenylketone group, whereas the first anodic was attributed to the xanthate unit. Macroelectrolysis on graphite and vitreous carbon at anodic and cathodic potentials, let us to explore the synthetic potential of this electrochemical reactions. With some compounds in hydroalcoholic media and using carbon electrodes, polymeric material was deposited on the electrode impeding the reaction; this deposit was characterized by AFM and SEM-EDS. The electroreduction on Ti electrode overcome this problem and gave the corresponding acetophenones (>95%). On the other hand, in ACN, small quantities of the dimeric 1,4-dicarbonyl compounds X-PhCOCH2CH2COPh-X (7–15%), as well as the corresponding acetophenones (ca. 50%) were isolated. Oxidation macroelectrolysis showed a very complicated transformation without synthetic value. The reaction mechanism for the reduction and the homolytic dissociation into the phenacyl radical was supported by DFT calculations.
- López-López, Ernesto Emmanuel,López-Jiménez, Sergio J.,Barroso-Flores, Joaquín,Rodríguez-Cárdenas, Esdrey,Tapia-Tapia, Melina,López-Téllez, Gustavo,Miranda, Luis D.,Frontana-Uribe, Bernardo A.
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- Copper(I)/DDQ-Mediated Double-Dehydrogenative Diels-Alder Reaction of Aryl Butenes with 1,4-Diketones and Indolones
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A copper(I)/DDQ-mediated double-dehydrogenative Diels-Alder (DDDA) reaction of simple butenes with 1,4-diketones and indolones has been established for the first time. This strategy is based on a tandem double-dehydrogenation/Diels-Alder reaction from nonprefunctionalized starting materials, in which both a diene and dienophile were in situ generated via activation of fourfold inert C(sp3)-H bonds in one catalytic system.
- Chen, Jie,Hu, Wei,Wang, Min,Xu, Wen-Lei,Zhao, Wei-Ming,Zhou, Ling
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supporting information
p. 7169 - 7174
(2020/10/12)
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- One-Pot Synthesis of O-Heterocycles or Aryl Ketones Using an InCl3/Et3SiH System by Switching the Solvent
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An efficient one-pot synthesis of O-heterocycles or aryl ketones has been achieved using Et3SiH in the presence of InCl3 via a sequential ionic hydrogenation reaction by switching the solvent. This methodology can be used to construct C-O bonds and to prepare conjugate reduction products, including chromans, tetrahydrofurans, tetrahydropyrans, dihydroisobenzofurans, dihydrochalcones, and 1,4-diones in a facile manner. In addition, a novel plausible mechanism involving a conjugate reduction and a tandem reductive cyclization was verified by experimental investigations.
- Jia, Wenqiang,Xi, Qiumu,Liu, Tianqi,Yang, Minjian,Chen, Yonghui,Yin, Dali,Wang, Xiaojian
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p. 5141 - 5149
(2019/05/10)
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- Lead-Halide Perovskites for Photocatalytic α-Alkylation of Aldehydes
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Cost-effective and efficient photocatalysis are highly desirable in chemical synthesis. Here we demonstrate that readily prepared suspensions of APbBr3 (A = Cs or methylammonium (MA)) type perovskite colloids (ca. 2-100 nm) can selectively photocatalyze carbon-carbon bond formation reactions, i.e., α-alkylations. Specifically, we demonstrate α-alkylation of aldehydes with a turnover number (TON) of over 52,000 under visible light illumination. Hybrid organic/inorganic perovskites are revolutionizing photovoltaic research and are now impacting other research fields, but their exploration in organic synthesis is rare. Our low-cost, easy-to-process, highly efficient and bandedge-tunable perovskite photocatalyst is expected to bring new insights in chemical synthesis.
- Zhu, Xiaolin,Lin, Yixiong,Sun, Yue,Beard, Matthew C.,Yan, Yong
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supporting information
p. 733 - 738
(2019/01/23)
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- Synthesis of 2,2,5-Trisubstituted 2 H-Pyrroles and 2,3,5-Trisubstituted 1 H-Pyrroles by Ligand-Controlled Site-Selective Dearomative C2-Arylation and Direct C3-Arylation
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Palladium-catalyzed site-selective dearomative C2-arylation of 2,5-diaryl-1H-pyrroles with aryl chlorides was accomplished, and a series of 2,2,5-triaryl-2H-pyrroles were synthesized. In addition, the site selectivity of the reaction was switched by simply changing the ligand, and the direct C3-arylated 2,3,5-triaryl-1H-pyrroles were prepared. The obtained 2,2,5-triaryl-2H-pyrroles could be further transformed into 2,2,5,5-tetraarylpyrrolidines.
- Yamaguchi, Miyuki,Fujiwara, Sakiko,Manabe, Kei
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supporting information
p. 6972 - 6977
(2019/09/03)
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- Synthesis of 1,4-Diketones via Titanium-Mediated Reductive Homocoupling of α-Haloketones
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1,4-Diketones have been synthesized via a reductive homocoupling of α-haloketones. Addition of a Grignard reagent to titanium(IV) isopropoxide affords a low-valent titanium(III) intermediate that is believed to mediate a radical dimerization reaction. The
- Le, Nathan N.,Rodriguez, Aimee M.,Alleyn, James R.,Gesinski, Michael R.
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p. 2195 - 2198
(2018/09/29)
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- Development of a Palladium-Catalyzed Carbonylative Coupling Strategy to 1,4-Diketones
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We report on a three-component palladium-catalyzed coupling strategy for accessing a wide range of 1,4-diketones, which represent important precursors to heterocycles. Our method relies on a carbonylative Heck reaction employing substituted allylic alcohols, aryl iodides, and carbon monoxide. The reaction conditions are mild and do not require high CO pressure, and a wide functional group tolerance is revealed, providing the desired 1,4-diketones in moderate to good yields. Furthermore, the methodology is adaptable to the selective installment of 13C-carbon isotopes at either one or both of the carbonyl positions.
- Yin, Hongfei,Nielsen, Dennis U.,Johansen, Mette K.,Lindhardt, Anders T.,Skrydstrup, Troels
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p. 2982 - 2987
(2016/07/06)
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- Breaking bonds with electrons: Stepwise and concerted reductive cleavage of C-S, C-Se and Se-CN bonds in phenacylthiocyanates and phenacylselenocyanates
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The mechanistic aspects of the electrochemical reduction of phenacylthio- and selenocyanates have been studied. With phenacylthiocyanates (1), a change in the reductive cleavage mechanism is observed as a function of the substituent on the phenyl ring. While a stepwise mechanism involving the intermediacy of a radical anion is followed for substrates bearing a strong electron withdrawing group, such as cyano and nitro substituent (1d, 1e), and a concerted mechanism is favoured for compounds bearing an electron-donating or no substituent on the phenyl ring (1a-c). A regioselective bond cleavage leads to the fragmentation of the CH2-S bond with all compounds 1a-e, further yielding the corresponding 1,4-diketone (3) as products. Contrastingly, with phenacylselenocyanates (2), two different reductive cleavages occur involving the breaking of both the CH2-Se and Se-CN bonds. Several products are obtained, all coming from nucleophilic attack at the α (phenacyl) carbon or the selenium atom.
- Bouchet, Lydia M.,Peory, Alicia B.,Robert, Marc,Argüello, Juan E.
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p. 11753 - 11760
(2015/02/19)
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- Flexible stereoselective functionalizations of ketones through umpolung with hypervalent iodine reagents
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The functionalization of carbonyl compounds in the α-position has gathered much attention as a synthetic route because of the wide biological importance of such products. Through polarity reversal, or "umpolung", we show here that typical nucleophiles, such as oxygen, nitrogen, and even carbon nucleophiles, can be used for addition reactions after tethering them to enol ethers. Our findings allow novel retrosynthetic planning and rapid assembly of structures previously accessible only by multistep sequences. A Nu approach: An efficient α-functionalization of ketones with a range of simple and useful nucleophiles is possible by using hypervalent iodine reagents (see scheme; Nu′ can be the Nu itself or a protected form of this nucleophile group).
- Mizar, Pushpak,Wirth, Thomas
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supporting information
p. 5993 - 5997
(2014/06/10)
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- Visible-light-induced Ci-S bond activation: Facile access to 1,4-diketones from β-ketosulfones
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A novel method for the synthesis of 1,4-diketones from β-ketosulfones was developed by means of a visible light-induced Ci£S bond activation process. Symmetrical and unsymmetrical 1,4-diketones can be easily prepared in moderate to good yields. A new and efficient method for the synthesis of 1,4-diketones from β-ketosulfones was developed by means of a visible-light-induced Ci£S bond activation process (see scheme). Symmetrical and unsymmetrical 1,4-diketones can be easily prepared in moderate to good yields.
- Xuan, Jun,Feng, Zhu-Jia,Chen, Jia-Rong,Lu, Liang-Qiu,Xiao, Wen-Jing
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supporting information
p. 3045 - 3049
(2014/03/21)
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- Efficient synthesis of γ-keto sulfones by NHC-catalyzed intermolecular Stetter reaction
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The N-heterocyclic carbene-catalyzed intermolecular Stetter reaction of aldehydes with α,β-unsaturated sulfones allows the atom-economic and selective formation of γ-keto sulfones in good yields. Key to the success of this unique transition-metal-free carbon-carbon bond-forming reaction is the right choice of the NHC precursor and base. The reaction tolerates a broad range of different aldehydes.
- Bhunia, Anup,Yetra, Santhivardhana Reddy,Bhojgude, Sachin Suresh,Biju, Akkattu T.
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supporting information; experimental part
p. 2830 - 2833
(2012/07/17)
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- Acylguanidine inhibitors of β-secretase: Optimization of the pyrrole ring substituents extending into the S1 and S3 substrate binding pockets
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Proteolytic cleavage of amyloid precursor protein by β-secretase (BACE-1) and γ-secretase leads to formation of β-amyloid (Aβ) a key component of amyloid plaques, which are considered the hallmark of Alzheimer's disease. Small molecule inhibitors of BACE-1 may reduce levels of Aβ and thus have therapeutic potential for treating Alzheimer's disease. We recently reported the identification of a novel small molecule BACE-1 inhibitor N-[2-(2,5-diphenyl-pyrrol-1-yl)-acetyl]guanidine (3.a.1). We report here the initial hit-to-lead optimization of this hit and the SAR around the aryl groups occupying the S1 and S2′ pockets leading to submicromolar BACE-1 inhibitors.
- Cole, Derek C.,Stock, Joseph R.,Chopra, Rajiv,Cowling, Rebecca,Ellingboe, John W.,Fan, Kristi Y.,Harrison, Boyd L.,Hu, Yun,Jacobsen, Steve,Jennings, Lee D.,Jin, Guixian,Lohse, Peter A.,Malamas, Michael S.,Manas, Eric S.,Moore, William J.,O'Donnell, Mary-Margaret,Olland, Andrea M.,Robichaud, Albert J.,Svenson, Kristine,Wu, JunJun,Wagner, Eric,Bard, Jonathan
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p. 1063 - 1066
(2008/09/19)
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- Synthesis of 1,4-diketones: reaction of α-bromo ketones with tetrakis(dimethylamino)ethylene (TDAE)
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1,4-Diketones were prepared by the reaction of α-bromo ketones with tetrakis(dimethylamino)ethylene (TDAE) in moderate to good yields. Similarly, α-bromo esters were reductively coupled using TDAE to give the 1,4-diesters in moderate yields.
- Nishiyama, Yutaka,Kobayashi, Akihiro
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p. 5565 - 5567
(2007/10/03)
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- One-step preparation of symmetrical 1,4-diketones from α-halo ketones in the presence of Zn-I2 as a condensation agent
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Eleven 1,4-diphenylbutane-1,4-diones have been prepared in one step from the corresponding α-halo acetophenones under the action of Zn-I 2 as a condensation agent with moderate to high yields. The mechanistic pathway of the reaction can be explained by the Wurtz-like self-condensation of α-halo ketones. Similarly, 3-chloropentane-2,4-dione gave 3,4-diacetylhexane-2,5-dione, a Wurtz-like condensation product.
- Ceylan, Mustafa,Guerdere, M. Burcu,Budak, Yakup,Kazaz, Cavit,Secen, Hasan
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p. 1750 - 1754
(2007/10/03)
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- Triphenylpyrylium salt-sensitized photoreactions of 1,4-diaryl-2,3- dioxabicyclo[2.2.2]octanes through competitive single electron-transfer pathway and proton-catalyzed pathway
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2,4,6-Triphenylpyrylium tetrafluoroborate (TPPBF4)-sensitized photoinduced electron-transfer (PET) reactions of 1,4-diaryl-2,3-dioxabicyclo[2. 2.2]octanes 5 (a: Ar1 = Ar2 = p-MeOC6H 4, b: Ar1 = Ar2 = p-MeC6H 4, c: Ar1 = Ar2 = Ph) underwent novel fragmentation through their radical cations to give 1,4-diarylbutan-1,4-diones 6 accompanied by elimination of ethylene. On the other hand, 4-aryl-cyclohex-3- en-1-ones 7, p-substituted phenols 8, and 4-aryl-4-aryloxycyclohexanones 9 were produced through proton-catalyzed pathways when the PET reactions of 5 were performed in the absence of a certain base such as 2,6-di-tert-butylpyridine (DTBP). Particularly, the formation of 9 is consistent with the novel cationic rearrangement involving nucleophilic O-1,2-aryl shifts and C-1,4-aryl shifts.
- Kamata, Masaki,Kaneko, Jun-Ichi,Hagiwara, Jun-Ichi,Akaba, Ryoichi
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p. 7423 - 7428
(2007/10/03)
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- Indium(I) bromide-mediated reductive coupling of α,α- dichloroketones to 1-aryl-butane-1,4-diones
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Indium(I) bromide promotes the reductive coupling of α,α- dichloroketones to the corresponding 1,4-butanediones in moderate to good yields.
- Peppe, Clovis,Pav?o Das Chagas, Rafael
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p. 1187 - 1190
(2007/10/03)
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- Fe(II)-mediated fragmentation of 1,4-diaryl-2,3-dioxabicyclo[2.2.2]octanes through competitive single electron transfer pathway and Lewis acid pathway
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Reactions of 1,4-diaryl-2,3-dioxabicyclo[2.2.2]octanes 1a-d (1a: Ar=p-FC6H4, 1b: Ar=Ph, 1c: Ar=p-MeC6H4, 1d: Ar=p-MeOC6H4) with FeBr2 in THF afforded 1,4-diarylbutan-1,4-diones 2a-d and 1,4-diaryl-7-oxabicyclo[2.2.1]heptanes 3a-d. On the other hand, 4-aryl-3-cyclohexenones 4c-d and p-substituted phenols 5c-d were obtained in the reactions of 1c-d with FeBr2 in CH2Cl2. A new fragmentation mechanism involving an electrophilic oxyl radical 1,5-substitution and a nucleophilic O-1,2-aryl shift is proposed based on the product analysis. In addition, the in vitro antimalarial activities of 1a-d were tested.
- Kamata, Masaki,Kudoh, Takashi,Kaneko, Jun-Ichi,Kim, Hye-Sook,Wataya, Yusuke
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p. 617 - 620
(2007/10/03)
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- Novel photo-rearrangement of 1,5-di(p-methoxyphenyl)-6,7-dioxabicyclo[3.2.2]nonane through an O-neophyl-type 1,2-aryl shift: Evidence for a 1,6-dioxyl diradical intermediate
-
Photolysis and thermolysis of 1,5-diaryl-6,7-dioxabicyclo[3.2.2]nonane 1a-c (a: Ar=p-MeOC6H4, b: Ar=p-MeC6H4, c: Ar=Ph) were investigated. (p-Methoxyphenyl)-substituted 1a underwent a novel photo-initiated O-neophyl-type 1,2-aryl shift to afford 1-(p-methoxyphenyl)oxy-5-(p-methoxyphenyl)-8-oxabicyclo[3.2.1]octane 7a along with a small amount of 1-(p-methoxyphenyl)-3-(2-(4′-methoxyphenyl)tetrahydrofuran-2-yl) propan-1-one 4a through an 1,6-dioxyl diradical intermediate, while the thermolysis mainly afforded the 1,5-di(p-methoxyphenyl)pentan-1,5-dione 5a and 1,4-di(p-methoxyphenyl)butan-1,4-dione 8a.
- Kamata, Masaki,Komatsu, Ken-Ichi
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p. 9027 - 9030
(2007/10/03)
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- Media controlled photo - Favorskii type rearrangement of α-chloro acetophenones: Synthesis of phenylacetic acids
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Photolysis of substituted α-chloro acetophenones has been studied in different solvent systems wherein 1,2-aryl migration is found to be media controlled. Effect of substituents on the migratory aptitude and a direct access to phenylacetic acids, in practical yields, has been described.
- Dhavale, Dilip D.,Mali, Vasant P.,Sudrik, Surendra G.,Sonawane, Harikisan R.
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p. 16789 - 16794
(2007/10/03)
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- The Reaction of Arylmagnesium Halides with Succinic Anhydride
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The reaction of equimolar amounts of phenylmagnesium bromide and succinic anhydride in THF at -78 deg for 2 h gives subsequent to hydrolytic work-up, 3-benzoylpropionic acid in 76percent yield and 4,4-diphenyl-4-butyrolactone in 3percent yield.When two molar equivalents of the Grignard reagent are employed, the yields of these products are respectively 85 and 14percent.On the other hand, when four equivalents of the Grignard reagent are employed for every equivalent of succinic anhydride at 66 deg C, a diketone, 1,4-diphenylbutane-1,4-dione is obtained in 72percent yield.Other products include 4,4-diphenyl-4-butyrolactone (19percent) and 3-benzoylpropionic acid (6percent).Under comparable conditions, 4-methyl- and 4-methoxyphenylmagnesium halides react similarly with succinic anhydride, giving fair yields (49-53percent) of the corresponding diketones.However, 4-chlorophenylmagnesium chloride only gives the keto-acid (12percent) and lactone (42percent), but no diketone.
- Rahman, M. T.,Nur, H. P.
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p. 469 - 474
(2007/10/02)
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- Reactions of carbanions from 2-(dialkylamino)-arylacetonitriles with acetylene - Simple syntheses of 1,3-dienamines and 1,4-diketones
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It has been found that morpholinonitrile 1a reacts with acetylene (2) in the presence of solid sodium hydroxide and tetrabutylammonium bromide (TBABr) as a catalyst, in DMSO, to give the vinyl derivative 3a. Whereas aminonitriles 1b-i, in the reaction with 2, afford dienamines 7. The different reactivity of 1a as compared to 1b-i is explained in terms of the different basicity of the amino moiety in vinyl derivatives 3. Dienamines 7 were hydrolyzed to 1,4-diarylbutan-1,4-diones 8 in high yields.
- Jonczyk, Andrzej,Lipiak, Dariusz,Zdrojewski, Tadeusz
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p. 1025 - 1038
(2007/10/02)
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- PHOTOCHEMISTRY OF α-PHENOXY-p-METHOXYACETOPHENONE
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The triplet state of the title compound decays by a competition of β-phenyl quenching and β-cleavage leading to CH3OC6H4COCH2. and phenoxyl radicals.The latter process occurs with a quantum yield of 0.020.
- Netto-Ferreira, J. C.,Scaiano, J. C.
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p. 443 - 446
(2007/10/02)
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- Carbon-Carbon Bond Formation Using Hypervalent Iodine Under Lewis Acid Conditions: Scope of the Method for the Synthesis of Butane-1,4-diones
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Hypervalent iodine oxidation of the silyl enol ethers of various acetophenones (2a-g), 2-acetylthiophenes (2i-k), 2-acetylfuran (2l) and 2-acetylbenzofuran (2m) with iodosobenzene-boron trifluoride-diethyl ether results in carbon-carbon coupling to yield the corresponding 1,4-disubstituted butane-1,4-dione (3a-m).Cross coupling (dissimilar coupling) between 4-methoxyacetophenone silyl enol ether (2c) and 4-nitroacetophenone silyl enol ether (2e) affords 1-(4-methoxyphenyl)-4-(4-nitrophenyl)butane-1,4-dione (27percent); the other minor products (3c) (18percent) and (3e) (15percent) resulting from similar coupling in this reaction.The sterically hindered aliphatic silyl enol ether (2h) obtained from pinacolone also undergoes smooth coupling whereas other aliphatic ketones do not.This method is likewise unsuccessful in case of nitrogen-containing heterocycles, viz. 2-,3-,4-acetylpyridine silyl enol ethers and tropinone silyl enol ether.
- Moriarty, Robert,Prakash, Om,Duncan, Michael P.
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p. 559 - 562
(2007/10/02)
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- SYNTHESIS OF 1,4-DIKETONES BY THE COUPLING REACTION OF TRIMETHYLSILYL ENOL ETHERS WITH LEAD TETRAACETATE
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Synthesis of 1,4-diketones in good yields was achieved by the coupling reaction of the trimethylsilyl enol ethers of acetophenone,thiophene or furan with lead tetraacetate in dry dichloromethane and tetrahydrofuran at -78 degC.
- Moriarty, Robert M.,Penmasta, Raju,Prakash, Indra
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p. 873 - 876
(2007/10/02)
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- NEW AND EFFICIENT DEHALOGENATIVE COUPLING AND REDUCTION OF α-HALOKETONES WITH ACTIVE NICKEL COMPLEX. FACILE SYNTHESES OF 1,4-DIKETONES AND BICYCLOOCT-3-ENE-2,5-DIONES
-
The active nickel complex generated in situ by reduction of NiBr2(PPh3)2 with zinc in the presence of Et4NI is a useful reagent for the dehalogenative coupling of phenacyl halides to 1,4-diaryl-1,4-diketones and for the dechlorination of 3,4-dichlorobicyclo-octane-2,5-diones to bicyclooct-3-ene-2,5-diones.
- Iyoda, Masahiko,Sakaitani, Masahiro,Kojima, Atsuko,Oda, Masaji
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p. 3719 - 3722
(2007/10/02)
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- Reactions of 4-Substituted-2'-Halogenoacetophenones with Grignard Reagents
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The initial reaction of 4-substituted 2'-halogenoacetophenones with an excess of methyl Grignard reagent is shown to be an attack at the 1'-carbonyl to form a halohydrin salt.The various reactions which then follow are substituent dependent.In the 4-hydroxy case the only product is 1-(4-hydroxyphenyl)-2-methylpropan-2-ol (13) which arises via a -aryl shift with simultaneous elimination of magnesium halide.When the substituent is 4-methoxy, a second pathway becomes important involving epoxide formation and a subsequent -hydride migration to the benzylic position, or attack of the Grignard reagent at the benzylic carbon of the epoxide.When the substituent is 4-bromo, the reaction proceeds exclusively via the epoxide and, following a -hydride shift, leads to the isomeric butanols (33) and (34).The reasons underlying such diversity of reactivity are discussed.
- Crombie, Leslie,Hardy, Robert,Knight, David W.
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p. 1373 - 1380
(2007/10/02)
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- Carbon-Carbon Bond Formation using Hypervalent Iodine under Lewis Acid Conditions: 1,4-Diarylbutane-1,4-diones
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Reaction of silyl enol ethers of aryl methyl ketones with PhIO-BF3*Et2O results in coupling to yield 1,4-diketones.
- Moriarty, Robert M.,Prakash, Om,Duncan, Michael P.
-
-
- ELECTROCHEMICAL OXIDATION OF AROMATIC OLEFINS. DEPENDENCE OF THE REACTION COURSE ON THE STRUCTURE OF THE OLEFINS AND ON THE NATURE OF THE ANODES
-
Anodic oxidation of a series of substituted styrenes was investigated in methanol with a platinum and a graphite electrode.Use of the platinum anode gave mainly dimethoxylated monomers accompanied wiht one or more of three types of dimethoxylated dimers (αα-, αβ-, and ββ-dimers) depending on the substituents.Use of the graphite anode, however, afforded the ββ-dimers as the main product together with dimethoxylated monomers.
- Kojima, Masanobu,Sakuragi, Hirochika,Tokumaru, Katsumi
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p. 1707 - 1710
(2007/10/02)
-