- Catalytic Enantioselective Total Synthesis of (+)-Lycoperdic Acid
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A concise enantio- and stereocontrolled synthesis of (+)-lycoperdic acid is presented. The stereochemical control is based on iminium-catalyzed Mukaiyama-Michael reaction and enamine-catalyzed organocatalytic α-chlorination steps. The amino group was introduced by azide displacement, affording the final stereochemistry of (+)-lycoperdic acid. Penultimate hydrogenation and hydrolysis afforded pure (+)-lycoperdic acid in seven steps from a known silyloxyfuran.
- Kortet, Sami,Claraz, Aurélie,Pihko, Petri M.
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- Antimalarially potent, easily prepared, fluorinated endoperoxides
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Three or four step chemical synthesis and in vitro antimalarial testing showed crystalline, thermally stable, bicyclic endoperoxides 3c and 4c to be potent antimalarials, having approximately 15% of the antimalarial activity of the clinically used, comple
- Posner, Gary H.,Tao, Xueliang,Cumming, Jared N.,Klinedinst, Donna,Shapiro, Theresa A.
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- 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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- Luminescent tungsten(vi) complexes as photocatalysts for light-driven C-C and C-B bond formation reactions
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The realization of photocatalysis for practical synthetic application hinges on the development of inexpensive photocatalysts which can be prepared on a large scale. Herein an air-stable, visible-light-absorbing photoluminescent tungsten(vi) complex which can be conveniently prepared at the gram-scale is described. This complex could catalyse photochemical organic transformation reactions including borylation of aryl halides, such as aryl chloride, reductive coupling of benzyl bromides for C-C bond formation, reductive coupling of phenacyl bromides, and decarboxylative coupling of redox-active esters of alkyl carboxylic acid with high product yields and broad functional group tolerance.
- Chan, Kaai-Tung,Che, Chi-Ming,Du, Lili,Liu, Yungen,Phillips, David Lee,To, Wai-Pong,Tong, Glenna So Ming,Wu, Liang-Liang,Yu, Daohong
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p. 6370 - 6382
(2020/07/15)
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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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- 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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- 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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- Synthesis and chemistry of 2,3-dioxabicyclo[2.2.2]octane-5,6-diols
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(Chemical Equation Presented) 1,4-Disubstituted 2,3-dioxabicyclo[2.2.2]oct- 5-enes were dihydroxylated with osmium tetroxide to yield diols anti to the peroxide linkage in a highly selective manner. Reduction of the peroxide bond furnished cyclohexane-1,2,3,4-tetraols with toxocarol relative stereochemistry in excellent yield. This new methodology was employed to synthesize the natural product (1S,2R,3S,4R,5R)-2-methyl-5-(propan-2-yl)cyclohexane-1,2,3,4-tetrol (1) in a short sequence from (R)-α-phellandrene. Moreover, during the study of the chemistry of 2,3-dioxabicyclo[2.2.2]octane-5,6-diols a hitherto unknown rearrangement was discovered which has wide applicability for the synthesis of 1,4-dicarbonyls, including optically enriched synthons. A broad range of mechanistic investigations applicable to this rearrangement are also reported.
- Valente, Peter,Avery, Thomas D.,Taylor, Dennis K.,Tiekink, Edward R. T.
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experimental part
p. 274 - 282
(2009/04/10)
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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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- 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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