- B(C6F5)3-Catalyzed Diastereoselective Formal (4 + 1)-Cycloaddition of Vinylcyclopropanes and Et2SiH2
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A formal (4 + 1)-cycloaddition of vinylcyclopropanes and Et2SiH2 to afford 3,4-disubstituted silolanes is reported. The reaction sequence commences with the known B(C6F5)3-catalyzed alkene hydrosilylation with dihydrosilanes. Cleavage of the remaining Si-H bond in the hydrosilylation product assisted by B(C6F5)3 leads to formation of a cyclopropane-stabilized silylium ion. The activated cyclopropane ring is then opened by the in situ-generated borohydride accompanied by ring closure to the silolane. The diastereoselectivity is rationalized by a mechanistic model.
- Long, Peng-Wei,Oestreich, Martin
-
supporting information
p. 4834 - 4837
(2021/06/28)
-
- Method for preparing carbonyl compound through oxidative cleavage of visible light excitation aqueous solution quantum dot catalytic olefin compound
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The invention provides a method for preparing carbonyl compounds through oxidative cleavage of a visible light excitation aqueous solution quantum dot catalytic olefin compound. Belong to photocatalysis synthesis technical field. To the method, an aqueous solution quantum dot is used as a photocatalyst, and an aqueous solution quantum dot activated molecular oxygen catalytic oxidation aromatic alkene compound is excited by visible light to be cracked to prepare a carbonyl compound. Low-loading capacity is used, a simple aqueous solution quantum dot is used as a catalyst, the yield of the carbonyl compound is high, TON more than ten millions are obtained. The reaction conditions are mild, water serves as a main solvent for the reaction, and the carbonyl compound can be obtained by catalytic olefin compound oxidation cracking without addition of a cocatalyst or the like. The method is simple to operate, wide in substrate range and low in cost.
- -
-
Paragraph 0039
(2021/11/10)
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- Cobalt-Catalyzed Radical Hydroamination of Alkenes with N-Fluorobenzenesulfonimides
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An efficient and general radical hydroamination of alkenes using Co(salen) as catalyst, N-fluorobenzenesulfonimide (NFSI) and its analogues as both nitrogen source and oxidant was successfully disclosed. A variety of alkenes, including aliphatic alkenes, styrenes, α, β-unsaturated esters, amides, acids, as well as enones, were all compatible to provide desired amination products. Mechanistic experiments suggest that the reaction underwent a metal-hydride-mediated hydrogen atom transfer (HAT) with alkene, followed by a pivotal catalyst controlled SN2-like pathway between in situ generated organocobalt(IV) species and nitrogen-based nucleophiles. Moreover, by virtue of modified chiral cobalt(II)-salen catalyst, an unprecedented asymmetric version was also achieved with good to excellent level of enantiocontrol. This novel asymmetric radical C?N bond construction opens a new door for the challenging asymmetric radical hydrofunctionalization.
- Lv, Guowei,Meng, Qi,Qin, Tao,Xiong, Tao,Zhang, Ge,Zhang, Qian
-
supporting information
p. 25949 - 25957
(2021/11/01)
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- Direct Access to Isotopically Labeled Aliphatic Ketones Mediated by Nickel(I) Activation
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An extensive range of functionalized aliphatic ketones with good functional-group tolerance has been prepared by a NiI-promoted coupling of either primary or secondary alkyl iodides with NN2 pincer NiII-acyl complexes. The latter were easily accessed from the corresponding NiII-alkyl complexes with stoichiometric CO. This Ni-mediated carbonylative coupling is adaptable to late-stage carbon isotope labeling, as illustrated by the preparation of isotopically labelled pharmaceuticals. Preliminary investigations suggest the intermediacy of carbon-centered radicals.
- Donslund, Aske S.,Pedersen, Simon S.,Gaardbo, Cecilie,Neumann, Karoline T.,Kingston, Lee,Elmore, Charles S.,Skrydstrup, Troels
-
supporting information
p. 8099 - 8103
(2020/03/16)
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- Aldehydes as Alkylating Agents for Ketones
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Common and non-toxic aldehydes are proposed as reagents for alkylation of ketones instead of carcinogenic alkyl halides. The developed reductive alkylation reaction proceeds in the presence of the commercially available ruthenium catalyst [(cymene)RuCl2]2 (as low as 250 ppm) and carbon monoxide as the reducing agent. The reaction works well for a broad substrate scope, including aromatic and aliphatic aldehydes and ketones. It can be carried out without a solvent and often gives nearly quantitative yields of the products. This straightforward and cost-effective method is promising not only for laboratory application but also for industry, which produces carbon monoxide as a large-scale waste product.
- Runikhina, Sofiya A.,Afanasyev, Oleg I.,Biriukov, Klim,Perekalin, Dmitry S.,Klussmann, Martin,Chusov, Denis
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supporting information
p. 16225 - 16229
(2019/11/22)
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- Iminyl Radical-Triggered Intermolecular Distal C(sp3)-H Heteroarylation via 1,5-Hydrogen-Atom Transfer (HAT) Cascade
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An efficient iron-catalyzed intermolecular remote C(sp3)-H heteroarylation of alkyl ketones has been developed via an iminyl radical-triggered 1,5-hydrogen-atom transfer (HAT) cascade. This protocol was amenable to a wide variety of alkyl ketones and heteroaryls, thus providing a straightforward method for the late-stage functionalization of alkylketones and heteroaryls.
- Gu, Yu-Rui,Duan, Xin-Hua,Chen, Li,Ma, Zhi-Yong,Gao, Pin,Guo, Li-Na
-
supporting information
p. 917 - 920
(2019/02/14)
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- A Lewis Base Catalysis Approach for the Photoredox Activation of Boronic Acids and Esters
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We report herein the use of a dual catalytic system comprising a Lewis base catalyst such as quinuclidin-3-ol or 4-dimethylaminopyridine and a photoredox catalyst to generate carbon radicals from either boronic acids or esters. This system enabled a wide range of alkyl boronic esters and aryl or alkyl boronic acids to react with electron-deficient olefins via radical addition to efficiently form C?C coupled products in a redox-neutral fashion. The Lewis base catalyst was shown to form a redox-active complex with either the boronic esters or the trimeric form of the boronic acids (boroxines) in solution.
- Lima, Fabio,Sharma, Upendra K.,Grunenberg, Lars,Saha, Debasmita,Johannsen, Sandra,Sedelmeier, Joerg,Van der Eycken, Erik V.,Ley, Steven V.
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supporting information
p. 15136 - 15140
(2017/11/20)
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- Borata-Wittig olefination reactions of ketones, carboxylic esters and amides with bis(pentafluorophenyl)borata-alkene reagents
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The strongly electrophilic borane derivative amino-CH2CH2CH2-B(C6F5)26 was α-CH deprotonated with LiTMP to give the borata-alkene {[amino-(CH2)2-CHB(C6F5)2-][Li+]}29 which underwent facile [2 + 2] cycloaddition reactions with benzophenone or fluorenone to yield the respective 1,2-oxaboretanides 11a,b. Compounds 9 and 11 were characterized by the X-ray diffraction. Thermolysis or hydrolysis of compounds 11a,b gave the corresponding borata-Wittig olefination products 12a,b. A variety of R-CH2-CH2-B(C6F5)2 boranes (conveniently generated by hydroboration of terminal alkenes R-CHCH2 with Piers' borane [HB(C6F5)2]) were analogously deprotonated to give the respective borata-alkenes 16a-e (R: Ph-CH2-, nC4H9, tBu, Cy, PhCH2CH2-). They underwent "non-classical" borata-Wittig olefination reactions with ethylformate to give the respective enolether carbonylation products, or their C1-elongated aldehydes (after hydrolysis). The borata-alkene [Ph-(CH2)2-CHB(C6F5)2-] [Li+HTMP] (16a) gave the respective "non-classical" borata-Wittig olefination products, the enolethers 25a,b and 27, respectively, upon treatment with methyl- or ethyl acetate or γ-butyrolactone.
- Wang, Tongdao,Kohrt, Sonja,Daniliuc, Constantin G.,Kehr, Gerald,Erker, Gerhard
-
supporting information
p. 6223 - 6232
(2017/08/02)
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- Decarboxylative Cross-Electrophile Coupling of N-Hydroxyphthalimide Esters with Aryl Iodides
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A new method for the decarboxylative coupling of alkyl N-hydroxyphthalimide esters (NHP esters) with aryl iodides is presented. In contrast to previous studies that form alkyl radicals from carboxylic acid derivatives, no photocatalyst, light, or arylmetal reagent is needed, only nickel and a reducing agent (Zn). Methyl, primary, and secondary alkyl groups can all be coupled in good yield (77% ave yield). One coupling with an acid chloride is also presented. Stoichiometric reactions of (dtbbpy)Ni(2-tolyl)I with an NHP ester show for the first time that arylnickel(II) complexes can directly react with NHP esters to form alkylated arenes.
- Huihui, Kierra M. M.,Caputo, Jill A.,Melchor, Zulema,Olivares, Astrid M.,Spiewak, Amanda M.,Johnson, Keywan A.,Dibenedetto, Tarah A.,Kim, Seoyoung,Ackerman, Laura K. G.,Weix, Daniel J.
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p. 5016 - 5019
(2016/05/19)
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- Highly Efficient Cooperative Catalysis by CoIII(Porphyrin) Pairs in Interpenetrating Metal–Organic Frameworks
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A series of porous twofold interpenetrated In-CoIII(porphyrin) metal–organic frameworks (MOFs) were constructed by in situ metalation of porphyrin bridging ligands and used as efficient cooperative catalysts for the hydration of terminal alkynes. The twofold interpenetrating structure brings adjacent CoIII(porphyrins) in the two networks parallel to each other with a distance of about 8.8 ?, an ideal distance for the simultaneous activation of both substrates in alkyne hydration reactions. As a result, the In-CoIII(porphyrin) MOFs exhibit much higher (up to 38 times) catalytic activity than either homogeneous catalysts or MOF controls with isolated CoIII(porphyrin) centers, thus highlighting the potential application of MOFs in cooperative catalysis.
- Lin, Zekai,Zhang, Zhi-Ming,Chen, Yu-Sheng,Lin, Wenbin
-
supporting information
p. 13739 - 13743
(2016/10/26)
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- Catalytic, Enantioselective Addition of Alkyl Radicals to Alkenes via Visible-Light-Activated Photoredox Catalysis with a Chiral Rhodium Complex
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An efficient enantioselective addition of alkyl radicals, oxidatively generated from organotrifluoroborates, to acceptor-substituted alkenes is catalyzed by a bis-cyclometalated rhodium catalyst (4 mol %) under photoredox conditions. The practical method provides yields up to 97% with excellent enantioselectivities up to 99% ee and can be classified as a redox neutral, electron-transfer-catalyzed reaction.
- Huo, Haohua,Harms, Klaus,Meggers, Eric
-
supporting information
p. 6936 - 6939
(2016/07/06)
-
- One-pot synthesis of benzene-fused medium-ring ketones: Gold catalysis-enabled enolate umpolung reactivity
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Enolate umpolung reactivities offer valuable and potentially unique alternatives over the enolate counterparts for the construction of ubiquitous carbonyl compounds. We disclose here that N-alkenoxypyridinium salts, generated readily upon gold-catalyzed additions of protonated pyridine N-oxide to C-C triple bonds of unactivated terminal alkynes, display versatile enolate umpolung chemistry upon heating and react with tethered arene nucleophiles in an SN2′ manner. In a synthetically efficient one-pot, two-step process, this chemistry enables expedient preparation of valuable benzo-fused seven-/eight-membered cyclic ketones, including those of O-/Nheterocycles, from easily accessible aryl-substituted linear alkyne substrates. The reaction yields can be up to 87%.
- Xu, Zhou,Chen, Hongyi,Wang, Zhixun,Ying, Anguo,Zhang, Liming
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p. 5515 - 5518
(2016/05/24)
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- A TEMPO-free copper-catalyzed aerobic oxidation of alcohols
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The copper-catalyzed aerobic oxidation of primary and secondary alcohols without an external N-oxide co-oxidant is described. The catalyst system is composed of a Cu/diamine complex inspired by the enzyme tyrosinase, along with dimethylaminopyridine (DMAP) or N-methylimidazole (NMI). The Cu catalyst system works without 2,2,6,6-tetramethyl-l-piperidinoxyl (TEMPO) at ambient pressure and temperature, and displays activity for un-activated secondary alcohols, which remain a challenging substrate for catalytic aerobic systems. Our work underscores the importance of finding alternative mechanistic pathways for alcohol oxidation, which complement Cu/TEMPO systems, and demonstrate, in this case, a preference for the oxidation of activated secondary over primary alcohols.
- Xu, Boran,Lumb, Jean-Philip,Arndtsen, Bruce A.
-
supporting information
p. 4208 - 4211
(2015/04/14)
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- Sunlight-driven trifluoromethylation of olefinic substrates by photoredox catalysis: A green organic process
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The principles and utility of photoredox catalysis in organic synthesis are described. After a brief description of the features of the two types of catalytic photoredox processes following the reductive quenching cycle (RQC) and the oxidative quenching cycle (OQC), the discussion is focused on organic transformations based on OQC, in particular the trifluoromethylation of olefinic substrates with electrophilic trifluoromethylating reagents furnishing solvolytic addition products and substitution products. It is concluded that catalytic photoredox systems are green from the point of view of harmfulness, safety, and energy source (visible light, including sunlight). Future prospects of photoredox catalysis will be also discussed.
- Akita, Munetaka,Koike, Takashi
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p. 742 - 751
(2015/07/15)
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- Supported Gold Nanoparticle-Catalyzed Hydration of Alkynes under Basic Conditions
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TiO2-supported nanosize gold particles catalyze the hydration of alkynes using morpholine as a basic cocatalyst. Unlike most homogeneous cationic gold catalysts, the TiO2-Au/morpholine system is weakly basic and is compatible with acid-sensitive functional groups (e.g., silyl ethers, ketals) or with a strongly coordinating group such as pyridine. What's more, this gold catalyst can be recycled by simple filtration and works well in flow reactors. (Chemical Equation Presented).
- Liang, Shengzong,Jasinski, Jacek,Hammond, Gerald B.,Xu, Bo
-
supporting information
p. 162 - 165
(2015/07/28)
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- Efficient Synthesis of N-Sulfonyl β -Arylmethylalaninates from Serine via Ring Opening of N-Sulfonyl Aziridine-2-carboxylate
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We report the efficient synthesis of N-sulfonyl β-arylalanines methyl ester through regioselective ring opening of N-protected aziridines by variety of heteroaryl C-nucleophiles. We have optimized synthesis of N-protected aziridines with versatile protecting groups to afford 4a-c, 6a, and 6b with moderate to good yields using sulfuryl chloride, triethyl amine, and toluene at -50 °C. The present work reports on the studies related to electronic effect of nitrogen substituent on aziridination from the inexpensive starting material DL-serine. The present investigation also reports the efficient synthesis of N-sulfonyl β-arylmethylalaninates (7a-e and 8a-e) by regioselective nucleophilic ring opening of N-sulfonamido-protected aziridines using various aryl moieties such as C-nucleophiles and Lewis acids (InCl3, FeCl3, Cu(OTf)2) as catalysts and some trials by ring opening using Grignard reagent. GRAPHICAL ABSTRACT.
- Chaudhari, Prashant,Bari, Sanjay
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p. 401 - 412
(2015/10/29)
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- Mechanism and Dynamics of Intramolecular C-H Insertion Reactions of 1-Aza-2-azoniaallene Salts
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The 1-aza-2-azoniaallene salts, generated from α-chloroazo compounds by treatment with halophilic Lewis acids, undergo intramolecular C-H amination reactions to form pyrazolines in good to excellent yields. This intramolecular amination occurs readily at both benzylic and tertiary aliphatic positions and proceeds at an enantioenriched chiral center with retention of stereochemistry. Competition experiments show that insertion occurs more readily at an electron-rich benzylic position than it does at an electron-deficient one. The C-H amination reaction occurs only with certain tethers connecting the heteroallene cation and the pendant aryl groups. With a longer tether or when the reaction is intermolecular, electrophilic aromatic substitution occurs instead of C-H amination. The mechanism and origins of stereospecificity and chemoselectivity were explored with density functional theory (B3LYP and M06-2X). The 1-aza-2-azoniaallene cation undergoes C-H amination through a hydride transfer transition state to form the N-H bond, and the subsequent C-N bond formation occurs spontaneously to generate the heterocyclic product. This concerted two-stage mechanism was shown by IRC and quasi-classical molecular dynamics trajectory studies. (Chemical Equation Presented).
- Hong, Xin,Bercovici, Daniel A.,Yang, Zhongyue,Al-Bataineh, Nezar,Srinivasan, Ramya,Dhakal, Ram C.,Houk,Brewer, Matthias
-
supporting information
p. 9100 - 9107
(2015/08/03)
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- A general method for the direct transformation of common tertiary amides into ketones and amines by addition of Grignard reagents
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The direct transformation of amides into ketones by addition of organometallic reagents has attracted the attention of organic chemists for a long time. However limited methods are reliable for common amides and have found synthetic applications. Here we report a method featuring in situ activation of tertiary amides with triflic anhydride (Tf2O) followed by addition of Grignard reagents. The method displays a good generality in scope for both amides and Grignard reagents, and it can be viewed as the acylation of Grignard reagents using amides as stable and selective acylating agents. Moreover, this deaminative alkylation reaction provides a mild method for the N-Deacylation of amides to give free amines.
- Huang, Pei-Qiang,Wang, Yu,Xiao, Kai-Jiong,Huang, Ying-Hong
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p. 4248 - 4254
(2015/06/02)
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- Selective oxidation of alcohols with alkali metal bromides as bromide catalysts: Experimental study of the reaction mechanism
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A bromide-catalyzed oxidation of alcohols was developed which proceeded in the presence of an alkali metal bromide and an oxidant under mild conditions. The reaction involved an organic-molecule-free oxidation using KBr and Oxone and a Br?nsted acid assisted oxidation using KBr and aqueous H 2O2 solution to provide a broad range of carbonyl compounds in high yields. Moreover, the bromide-catalyzed oxidation of primary alcohols enabled the divergent synthesis of carboxylic acids and aldehydes under both reaction conditions in the presence of TEMPO. A possible catalytic mechanism was suggested on the basis of various mechanistic studies.
- Moriyama, Katsuhiko,Takemura, Misato,Togo, Hideo
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p. 6094 - 6104
(2014/07/21)
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- Scope and mechanism in palladium-catalyzed isomerizations of highly substituted allylic, homoallylic, and alkenyl alcohols
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Herein we report the palladium-catalyzed isomerization of highly substituted allylic alcohols and alkenyl alcohols by means of a single catalytic system. The operationally simple reaction protocol is applicable to a broad range of substrates and displays a wide functional group tolerance, and the products are usually isolated in high chemical yield. Experimental and computational mechanistic investigations provide complementary and converging evidence for a chain-walking process consisting of repeated migratory insertion/β-H elimination sequences. Interestingly, the catalyst does not dissociate from the substrate in the isomerization of allylic alcohols, whereas it disengages during the isomerization of alkenyl alcohols when additional substituents are present on the alkyl chain.
- Larionov, Evgeny,Lin, Luqing,Gune, Laure,Mazet, Clment
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supporting information
p. 16882 - 16894
(2015/01/09)
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- Acid-catalyzed oxidative radical addition of ketones to olefins
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Based on a mechanistic study, we have discovered a Bronsted acid catalyzed formation of ketone radicals. This is believed to proceed via thermally labile alkenyl peroxides formed in situ from ketones and hydroperoxides. The discovery could be utilized to develop a multicomponent radical addition of unactivated ketones and tert-butyl hydroperoxide to olefins. The resulting γ-peroxyketones are synthetically useful intermediates that can be further transformed into 1,4-diketones, homoaldol products, and alkyl ketones. A one-pot reaction yielding a pharmaceutically active pyrrole is also described.
- Schweitzer-Chaput, Bertrand,Demaerel, Joachim,Engler, Hauke,Klussmann, Martin
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p. 8737 - 8740
(2014/08/18)
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- Palladium-catalyzed hydrogenation with use of ionic liquid bis(2-hydroxyethyl)ammonium formate [BHEA][HCO2] as a solvent and hydrogen source
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We designed ionic liquid bis(2-hydroxyethyl)ammonium formate [BHEA][HCO2] for use as a solvent and hydrogen donor for hydrogenation. Catalytic hydrogenation of aromatic ketones, nitro groups, and olefins with PdCl2 in [BHEA][HCO2] generated the corresponding reduction products. Selective reduction of aromatic ketones over aliphatic ketones was observed. Hydrogenolysis of benzyl ethers and benzyl amines also proceeded. All these reactions were successfully carried out in good to excellent yields under mild and nonflammable conditions. In addition, the ionic liquid and Pd source can be reused several times.
- Suzuki, Hideyuki,Yoshioka, Seiki,Igesaka, Ami,Nishioka, Hiromi,Takeuchi, Yasuo
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p. 6399 - 6403
(2013/07/25)
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- Synthesis and neuroprotective effect of E-3,4-dihydroxy styryl aralkyl ketones derivatives against oxidative stress and inflammation
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E-3,4-Dihydroxy styryl aralkyl ketones as well as their 3,4-diacetylated derivatives as the analogues of neuroprotective agent CAPE were designed and synthesized for improving stability and lipid solubility. The neuroprotective activities of target compounds 10a-g and 11a-g were tested by three models in vitro, including 1,1-diphenyl-2-picrylhydrazyl radical scavenging capacity, neuronal protecting effect against damage induced by H2O2 in PC12 cells and nitric oxide suppression effect in BV2 microglial cells. The results demonstrated that compounds 10f and 11f exhibited the most potent neuroprotective effect against oxidative stress and inflammation, which is higher than that of the lead compound CAPE.
- Ning, Xianling,Guo, Ying,Ma, Xiaoyan,Zhu, Renzong,Tian, Chao,Wang, Xiaowei,Ma, Zhizhong,Zhang, Zhili,Liu, Junyi
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p. 3700 - 3703
(2013/07/25)
-
- Synthesis of (±)-bimatoprost
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A general synthetic approach has been developed for the synthesis of a key intermediate (6) that can be elaborated into several ophthalmic prostaglandins and their derivatives. Using these strategy, we have obtained (±)-bimatoprost (1) and its analog, (±)-homobimatoprost (5). Copyright Taylor & Francis Group, LLC.
- Harikrishna,Mohan, H. Rama,Dubey,Shankar,Subbaraju, Gottumukkala V.
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experimental part
p. 1288 - 1305
(2012/04/10)
-
- Novel reactivity of N-bridged diiron phthalocyanine in the activation of C-H bonds: Hydroacylation of olefins as an example of the efficient formation of C-C bonds
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Bridge over troubled iron: An N-bridged diiron tetra-tert- butylphthalocyanine complex, usually employed for oxidation reactions, also catalyzes the addition of acetaldehyde to olefins (see scheme) to provide methylketones with a high selectivity (up to 92%) and high turnover numbers (3600-5700). Copyright
- Alvarez, Leonardo X.,Kudrik, Evgeny V.,Sorokin, Alexander B.
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supporting information; experimental part
p. 9298 - 9301
(2011/10/09)
-
- Trifluoromethanesulfonic acid catalyzed isomerization of kinetic enol derivatives to the thermodynamically favored isomers
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Trifluoromethanesulfonic acid catalyzed isomerization of kinetic enol derivatives to the thermodynamically favored isomers was developed. Under the present conditions, kinetic enol phosphates, enol acetates and benzoates, and enol sulfonates were smoothly isomerized to produce the corresponding thermodynamically favored isomers in good to excellent yields.
- Lee, Phil Ho,Kang, Dongjin,Choi, Subin,Kim, Sunggak
-
supporting information; experimental part
p. 3470 - 3473
(2011/08/22)
-
- Organic electrosynthesis using toluates as simple and versatile radical precursors
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The electrolysis of toluate esters leads smoothly to the formation of the radical of the alkyl fragment. This property has been used to develop a new electrochemical deoxygenation reaction. The Royal Society of Chemistry.
- Lam, Kevin,Marko, Istvan E.
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experimental part
p. 95 - 97
(2009/03/11)
-
- Toluates: unexpectedly versatile reagents
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The mechanism of the monoelectronic reduction of aromatic esters has been investigated. The unexpected synthetic utility of the toluate moiety in the deoxygenation of alcohols and the allylation of ketones is also reported. Finally, the use of aromatic esters as robust, though easily removable, protecting groups is depicted.
- Lam, Kevin,Markó, István E.
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experimental part
p. 10930 - 10940
(2010/02/28)
-
- Samarium diiodide mediated ketyl-aryl coupling reactions - Influence of substituents and trapping experiments
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This comprehensive study describes the influence of substituents at the aryl moiety on SmI2-mediated intramolecular ketyl-aryl coupling reactions. Differently substituted γ-aryl ketones were employed as precursors, which were directly prepared
- Wefelscheid, Ulrike K.,Berndt, Mathias,Reissig, Hans-Ulrich
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experimental part
p. 3635 - 3646
(2009/06/06)
-
- Cyclopropyl conjugation and ketyl anions: When do things begin to fall apart?
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Results pertaining to the electrochemical reduction of 1,2- diacetylcyclopropane (5), 1-acetyl-2-phenylcyclopropane (6), 1-acetyl-2-benzoylcyclopropane (7), and 1,2-dibenzoylcyclopropane (8) are reported. While 6?- exists as a discrete species, the barrier to ring opening is very small (107 s-1. For 7 and 8, the additional resonance stabilization afforded by the benzoyl moieties results in significantly lower rate constants for ring opening, on the order of 10 5-106 s-1. Electron transfer to 8 serves to initiate an unexpected vinylcyclopropane → cyclopentene type rearrangement, which occurs via a radical ion chain mechanism. The results for reduction of 5 are less clear-cut: The experimental results suggest that the reduction is unexceptional, with a symmetry coefficient α ≤ 0.5, and reorganization energy consistent with a simple electron-transfer process (one electron reduction, followed by ring opening). In contrast, molecular orbital calculations suggest that 5?- has no apparent lifetime and that reduction of 5 may occur by a concerted dissociative electron transfer (DET) mechanism (i.e., electron transfer and ring opening occur simultaneously). These seemingly contradictory results can be reconciled if the increase in the internal reorganization energy associated with the onset of concerted DET is offset by a lowering of the solvent reorganization energy associated with electron transfer to a more highly delocalized LUMO.
- Tanko,Li, Xiangzhong,Chahma, M'Hamed,Jackson, Woodward F.,Spencer, Jared N.
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p. 4181 - 4192
(2008/02/01)
-
- Direct addition of supercritical alcohols, acetone or acetonitrile to the alkenes without catalysts
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The reactions of the alkenes with supercritical organic compounds under non-catalytic conditions were investigated. The H and CR2OH, CH2C{double bond, long}OCH3 or CH2C{triple bond, long}N of supercritical alcohols (CHR2OH), acetone (CH3C{double bond, long}OCH3) or acetonitrile (CH3C{triple bond, long}N) added to the C{double bond, long}C bonds of alkenes form C-C bonds between the α-carbons of the supercritical organic compounds and the sp2 carbons of the alkenes.
- Kamitanaka, Takashi,Hikida, Tatsuyoshi,Hayashi, Satoshi,Kishida, Nobuhiro,Matsuda, Tomoko,Harada, Tadao
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p. 8460 - 8463
(2008/03/13)
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- Preparation of aliphatic ketones through a ruthenium-catalyzed tandem cross-metathesis/allylic alcohol isomerization
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Grubbs' 2nd generation and Hoveyda-Grubbs' ruthenium alkylidenes are shown to be effective catalysts for cross-metatheses of allylic alcohols with cyclic and acyclic olefins, as well as isomerization of the resulting allylic alcohols to alkyl ketones. The net result of this new tandem methodology is a single-flask process that provides highly functionalized, ketone-containing products from simple allylic alcohol precursors.
- Finnegan, David,Seigal, Benjamin A.,Snapper, Marc L.
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p. 2603 - 2606
(2007/10/03)
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- Samarium diiodide induced reactions of cyclopropyl ketones: Reductive ring cleavage and dimerization leading to 1,8-diketones - Scope, limitations, mechanisms
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Reactions of the samarium diiodide/HMPA complex with alkyl cyclopropyl ketones such as 3, 5, and 7 provided dimers incorporating a 1,8-diketone moiety. The products 4, 6, and 8 were isolated in moderate to good yields. The aryl-substituted cyclopropyl ketones afforded a broader product spectrum, which results from the attack of samarium intermediates to the aryl group. Cyclopropyl phenyl ketone (13) gave dimer 14, where one cyclopropane ring was reductively cleaved, whereas the second one is still present. The reductive dimerization of cyclopropyl 2-thienyl ketone (21) furnished the product 22, which still contains two cyclopropyl groups. Further examples demonstrate the diversity of samarium diiodide induced reductions of cyclopropyl ketones. Plausible reaction mechanisms involving samarium ketyl intermediates are presented. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Aulenta, Francesca,Hoelemann, Alexandra,Reissig, Hans-Ulrich
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p. 1733 - 1739
(2007/10/03)
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- Facile oxidative conversion of alcohols to esters using molecular iodine
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A simple, efficient, and high-yield procedure for the oxidative conversion of alcohols to various types of esters and ketones, with molecular iodine and potassium carbonate was successfully carried out.
- Mori, Naoshi,Togo, Hideo
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p. 5915 - 5925
(2007/10/03)
-
- Free radical-promoted conjugate addition of activated bromo compounds using titanocene(III) chloride as the radical initiator
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Free radical-promoted conjugate addition of activated bromo compounds to α,β-unsaturated ketones and reactive α,β-unsaturated esters has been described using titanocene(III) chloride (Cp2TiCl) as the radical initiator. Cp2TiCl was prepared in situ from commercially available Cp2TiCl2 and activated zinc dust in THF.
- Mandal, Samir Kumar,Jana, Samaraesh,Roy, Subhas Chandra
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p. 6115 - 6117
(2007/10/03)
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- Ruthenium-catalyzed hydrative dimerization of allenes
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Hydrative dimerization and hydration of allenes proceeded in the presence of a ruthenium catalyst and a strong acid such as trifluoroacetic acid. γ,δ-Unsaturated ketones and methyl ketones were isolated in moderate combined yields. No isomeric compound (isomeric enone) was isolated. Copyright
- Saito, Shinichi,Dobashi, Naotomo,Wakatsuki, Yasuo
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p. 504 - 505
(2007/10/03)
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- Reaction of unstabilized iodonium ylides with organoboranes
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Exposure of monocarbonyl iodonium ylides, generated by the ester exchange of (Z)-(2-acetoxyvinyl)-λ3-iodanes with EtOLi, to organoboranes results in a 1,2-shift of a carbon ligand from boron to the ylide carbons, which probably generates hitherto uncharacterized α-boryl ketones.
- Ochiai, Masahito,Tuchimoto, Yoshimi,Higashiura, Nobuyuki
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p. 1505 - 1508
(2007/10/03)
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- Pd(0)-Catalyzed Conjugate Addition of Benzylzinc Chlorides to α,β-Enones in An Atmosphere of Carbon Monoxide: Preparation of 1,4-Diketones
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Pd(0)-catalyzed conjugate addition of benzylzine chloride to methyl vinyl ketone in the presence of chlorotrimethylsilane and lithium chloride in an atmosphere of carbon monoxide at room temperature afforded 1-phenyl-2,5-hexanedione monosilyl enol ether. In this catalytic carbonylation, four components are connected in one reaction. Successive acidic workup generated a variety of 1,4-diketones from substituted benzylzine chlorides or related compounds and α,β-enones. Some products were converted to cyclopentenones or five-membered heterocyclic compounds containing an N, O, or S atom.
- Yuguchi, Motoki,Tokuda, Masao,Orito, Kazuhiko
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p. 908 - 914
(2007/10/03)
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- Organophosphorus compounds and the use thereof
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The invention relates to organophosphorus compounds of general formula (I) wherein A corresponds to general formula (II), wherein one or more of the carbon atoms, selected from the group C3, C4, C5and their respective substituents can be omitted, and at least one substituent of B1to B10is a C3-8cycloalkyl (C0-9) alkyl group, wherein both the C3-8cycloalkyl group and the C0-9alkyl group can have one or more double bonds and one or two carbon atoms of the cycloalkyl group can be substituted by nitrogen, oxygen or sulfur atoms, and wherein both the cycloalkyl group and the alkyl group can be substituted by hydrogen, halogen amine, oxo groups with branched or unbranched C1-9alkyl groups and C2-9alkenyl groups, wherein the C1-9alkyl groups and C2-9alkenyl groups can be substituted by hydrogen, hydroxy, amine, halogen, and oxo groups. The invention further relates to pharmaceutical preparations containing said compounds and to the use thereof for the therapy and prophylaxis of infectious processes in humans and animals, which processes are induced by bacteria, fungi or parasites. The inventive compounds are also used as fungicidal, bactericidal or herbicidal agents in plants.
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- New ketone homoenolate anion equivalents derived from (alkenyl)pentamethyl phosphoric triamides
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Lithiated ambident anions derived from (1-alkyl-2-propenyl)- or (1-phenyl-2-propenyl)-pentamethyl phosphoric triamides undergo regioselectively γ-reaction with various alkylating reagents and isobutyraldehyde. Further hydrolysis of adducts releases the ketone under acid conditions. Number of synthetic applications clearly show the ketone homoenolate behaviour of these new carbanions.
- Grison, Claude,Thomas, Antoine,Coutrot, Frédéric,Coutrot, Philippe
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p. 2101 - 2123
(2007/10/03)
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- An efficient synthesis of vinylsilanes from acylsilanes and alkyl 1-phenyl-1H-tetrazol-5-yl sulfones. Brook vs smiles rearrangement
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Matrix presented Vinylsilanes are formed in high yields in the reaction of representative acyl(trimethyl)silanes with anions generated from Kocienski's sulfones.
- Jankowski, Pawel,Plesniak, Krzysztof,Wicha, Jerzy
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p. 2789 - 2792
(2007/10/03)
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- Synthesis and DHFR inhibitory activity of a series of 6-substituted-2,4-diaminothieno[2,3-d]pyrimidines
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A series of 6-aralkyl substituted 2,4-diaminothieno[2,3-d]pyrimidines in which the 6-aryl group is separated from the thieno[2,3-d]pyrimidine ring by two to five methylene groups were synthesized and studied as inhibitors of dihydrofolate reductase from Pneumocystis carinii, Toxoplasma gondii, Mycobacterium avium, and rat liver. Compounds in which the thieno[2,3-d]pyrimidine ring is separated from the 6-aryl substituent by three methylene groups were the most potent inhibitors of the series (with IC50 values ranging from 0.24 and 11.0 μM) but those with two methylene groups between the aromatic rings were the most selective agents.
- Donkor, Isaac O.,Li, Hui,Queener, Sherry F.
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p. 605 - 611
(2007/10/03)
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- Cleavage of cyclopropyl ketones mediated by alkylmercury(II) hydrides
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Cyclopropyl ketones are converted into their hydrazones which react with mercury(II) oxide and mercury(II) acetate to give α-(acetoxymercurio)alkyl acetates. These are reducedin situ to the corresponding α-acetoxyalkylmercury(II) hydrides which rearrange spontaneously with cleavage of the cyclopropane ring. The procedure is used to obtain D-homo- and 17(13→18)-abeo-pregnanes.
- Di Chenna, Pablo H.,Andre Ferrara,Ghini, Alberto A.,Burton, Gerardo
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p. 227 - 231
(2007/10/03)
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- Chemoselective control of hydrogenation among aromatic carbonyl and benzyl alcohol derivatives using Pd/C(en) catalyst
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The hydrogenolysis of aromatic ketones and aldehydes quite smoothly give the corresponding methylene compounds via the formation of the intermediary benzyl alcohols in the presence of Pd/C as a catalyst. Therefore, it is extremely difficult to isolate the intermediary benzyl alcohol selectively. This paper describes a mild and chemoselective hydrogenation method of an aromatic carbonyl compound to benzyl alcohol using the 10% Pd/C(en) catalyst and its application to the chemoselective deacetoxylation reaction at the benzylic position in the presence of the benzyl alcohol functionality within the molecule.
- Hattori, Kazuyuki,Sajiki, Hironao,Hirota, Kosaku
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p. 4817 - 4824
(2007/10/03)
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- Barbier-type reactions of nitriles and alkyl iodides mediated by samarium(II) iodide in the presence of catalytic nickel(II) iodide
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The samarium(II) iodide-mediated intermolecular Barbier-type reactions of nitriles and alkyl iodides have been investigated. In the presence of a catalytic amount of nickel(II) iodide, the reaction proceeded smoothly to provide the corresponding ketones. Amides also reacted to give ketones under the same Barbier-type conditions. (C) 2000 Elsevier Science Ltd.
- Kang, Han-Young,Song, Sang-Eun
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p. 937 - 939
(2007/10/03)
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- Hydroxyl-directed intermolecular ketone-olefin couplings promoted by SmI2
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SmI2-promoted intermolecular ketone-olefin couplings are facilitated and stereocontrolled by hydroxyl groups incorporated within the starting materials. For example, the SmI2-induced ketone-olefin coupling reactions of α-hydroxy ketone 5 with ethyl acrylate, acrylonitrile, ethyl crotonate, and 2(5H)-furanone proceeded with high stereocontrol to afford the syn-1,2-diol products 6-9 in good yields. Excellent diastereoselectivity was achieved in the reductive couplings of β-hydroxy aldehyde 21 and erythro-β-hydroxy ketone 24 with acrylonitrile using SmI2, to produce the anti-1,3-diols 22 and 25 in good yields. The sense of the stereoselectivity was in full accord with a chelation-control model. In the proposed model, the stereochemistry of the reaction product is explained by assuming that a cyclic ketyl radical is generated during the initial single-electron reduction by SmI2. This radical species results from the chelation of the Sm(III) cation, attached to the ketyl radical, with the hydroxyl group.
- Matsuda,Kawatsura,Hosaka,Shirahama
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p. 3252 - 3259
(2007/10/03)
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- Hydration of Alkynes by a PtCl4-CO Catalyst
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Treatment of PtCl4 with CO at 40-110°C forms a powerful alkyne hydration catalyst that operates both under homogeneous conditions in wet THF and under phase-transfer conditions in (CHCl2)2/H2O in the presence of tricaprylmethylammonium chloride (Aliquat 336). Complex HPtCl(CO)2 is regarded as the active hydration catalyst. It is assumed to be formed by initial transformation of PtCl2 to H2[Pt3(CO)6]n (n = 5, 6) followed by reaction with HCl (generated by decomposition of the starting platinum salt).
- Baidossi, Wa?l,Lahav, Michal,Blum, Jochanan
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p. 669 - 672
(2007/10/03)
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- The Zinc-Trifluoroacetic Acid Reaction in Organic Solvents: A Facile Procedure for the Conversion of Nitroolefins into Carbonyl Compounds under Mild Conditions
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It has been demonstrated that nitroolefins are efficiently converted into the corresponding carbonyl compounds by reaction with stoichiometric amounts of zinc and trifluoroacetic acid in organic solvents like DMF, methanol etc.
- Saikia, Anil K.,Barua, Nabin C.,Sharma, Ram P.,Ghosh, Anil C.
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p. 124 - 125
(2007/10/03)
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- Surface-Mediated Reactions. 6. Effects of Silica Gel and Alumina on Acid-Catalyzed Reactions
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Absorption of a variety of acids to chromatographic silica gel results in substantial enhancement of their catalytic activity-affording easily prepared, environmentally benign heterogeneous acids that are highly effective in mediating a number of processes.This was shown for the isomerization of allene 1 and dimerization of the corresponding 1,3-diene 2; cyclization of (R)-citronellal (5), the related diester 10, and 1,5-cyclooctadiene (15); Rupe rearrangement of alkynol 18; and Friedel-Crafts cyclodehydration of alcohols 21.By contrast, commercially available Nafion-H was significantly less effective as a heterogeneous acid catalyst.Chromatographic alumina displayed enigmatic behavior, showing enhanced acidity on the adsorption of HCl but little or no acidity on the adsorption of a variety of other types of acid.The results are discussed in terms of the surface structures of silica gel and alumina.
- Kropp, Paul J.,Breton, Gary W.,Craig, Stephen L.,Crawford, Scott D.,Durland, William F.,et al.
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p. 4146 - 4152
(2007/10/02)
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