- Hypoiodous acid-catalyzed regioselective geminal addition of methanol to vinylarenes: synthesis of anti-Markovnikov methyl acetals
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A novel metal-free, catalytic geminal dimethoxylation of vinylarenes based on in situ generated HOI species from iodide salt and oxone is reported. The preliminary mechanistic investigations suggest that the key factor for achieving the anti-Markovnikov regioselectivity is the semipinacol rearrangement of an iodo functionalized intermediate, which is confirmed by an isotope labeling experiment. In addition, the reaction involves the de-iodination of a co-iodo intermediate via its oxidation to hypervalent iodine species rather than a common iodide abstraction by electrophiles. The HRESI-MS studies support the conversion of monovalent iodine containing intermediates to trivalent iodine intermediates during the catalytic conversion of aromatic alkenes into the corresponding terminal acetals.
- Peraka, Swamy,Mameda, Naresh,Marri, Mahender Reddy,Kodumuri, Srujana,Chevella, Durgaiah,Sripadi, Prabhakar,Nama, Narender
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- An efficient protection of carbonyls and deprotection of acetals using decaborane
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Carbonyls were efficiently converted to the corresponding dimethyl acetals at room temperature using trimethyl orthoformate and 1 mol% of decaborane under a nitrogen atmosphere. In turn, acetals were deprotected to the corresponding carbonyls using 1 mol% of decaborane in aqueous THF chemoselectively.
- Lee, Seung Hwan,Lee, Ji Hee,Yoon, Cheol Min
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- Termolecular Trapping of Benzylchlorocarbene by Methanol
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The trapping of benzylchlorocarbene by methanol is termolecular leading to a frequency factor of 2 x 105 l2 mol-2 s-1 and an activation energy of -4.5 kcal mol-1 (18.8 kJ mol-1).
- Liu, Michael T. H.,Subramanian, Ramasamy
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- Atom-economical synthesis of 3,3,3-trifluoropropanal dialkyl acetals through Pd/C catalyzed acetalization of 3,3,3-trifluoropropene
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A facile and efficient procedure for one-step synthesis of 3,3,3-trifluoropropanal dialkyl acetals from readily available 3,3,3-trifluoropropene (TFP) has been developed. The catalyst can be recycled for 4 times without obvious deactivation. This process provides a novel and atom-economical synthetic strategy for the preparation of functional CF3-containing compounds.
- Kang, Jian-Ping,Lu, Ju-You,Li, Yang,Wang, Zhi-Xuan,Mao, Wei,Lu, Jian
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- Reactivity of hydroxy- and aquo(hydroxy)-λ3-iodane-crown ether complexes
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We have designed a series of hydroxy(aryl)-λ3-iodane-[18] crown-6 complexes, prepared from the corresponding iodosylbenzene derivatives and superacids in the presence of [18]crown-6, and have investigated their reactivities in aqueous media. These activated iodosylbenzene monomers are all non-hygroscopic shelf-storable reagents, but they maintain high oxidizing ability in water. The complexes are effective for the oxidation of phenols, sulfides, olefins, silyl enol ethers, and alkyl(trifluoro)borates under mild conditions. Furthermore, hydroxy-λ3-iodane-[18]crown-6 complexes serve as efficient progenitors for the synthesis of diaryl-, vinyl-, and alkynyl-λ3-iodanes in water. Other less polar organic solvents, such as methanol, acetonitrile, and dichloromethane, are also usable in some cases. Aqua-friendly iodosylbenzene equivalents: Hydroxy- and aquo(hydroxy)-λ3-iodane-[18]crown-6 complexes (see graphic), readily prepared from commercial PhI(OAc)2 or PhIO, serve as excellent oxygen atom donors toward olefins, phenols, sulfides, and alkyl(trifluoro)borates. They also serve as progenitors for diaryl-, vinyl-, and alkynyl-λ3-iodane-[18]crown-6 complexes. These reactions can be carried out in aqueous media under mild reaction conditions.
- Miyamoto, Kazunori,Yokota, Yukie,Suefuji, Takashi,Yamaguchi, Kentaro,Ozawa, Tomoyuki,Ochiai, Masahito
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- Palladium-catalyzed aerobic oxidation of terminal olefins with electron-withdrawing groups in scCO2
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Product control of palladium-catalyzed aerobic oxidation of terminal olefins with electron-withdrawing groups can be achieved through modifying reaction conditions. When the oxidant, such as CuCl2/O2, benzoquinone/O2 or O2, was present in scCO2, aerobic oxidation of terminal olefins goes smoothly. With enough MeOH and sufficient oxygen, acetalization preponderated over cyclotrimerization, while with little MeOH as co-solvent in scCO2 or no MeOH in DMF and an appropriate pressure of O2, cyclotrimerization of terminal olefins became the dominated reaction. When oxygen is absent and triethylamine was added into the reaction system, palladium-catalyzed C-N bond formation occurs to produce β-amino acid derivatives as the sole product.
- Jiang, Huan-Feng,Shen, Yan-Xia,Wang, Zhao-Yang
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- Synthesis, structure and catalytic activity of a gold(i) complex containing 1,2-bis(diphenylphosphino)benzene monoxide
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The gold(i) complex [Au(dppbO)Cl] was synthesized by reaction of Na[AuCl4]·2H2O with 1,2-bis(diphenylphosphino)benzene (dppb) in the presence of water. This is a new method for the synthesis of a bisphosphine monoxide gold(i) complex. The new gold(i) complex was characterized by NMR spectroscopy and X-ray crystal structure analysis. In the solid state structure a relatively short contact between the oxygen atom of the phosphine oxide group and the gold center was observed. The catalytic activity of [Au(dppbO)Cl] was tested for three different intermolecular alkyne hydrofunctionalization reactions. Silver tetrafluoroborate was used as co-catalyst for halide abstraction. While the bisphosphine monoxide gold(i) complex showed moderate activity for the hydration of various alkynes and the hydroamination of phenyl acetylene, high activity was observed for the hydroarylation of ethylpropiolate. Electron-rich arenes add very fast to the C-C triple bond but with relatively low selectivity.
- Hahn, Christine,Cruz, Leticia,Villalobos, Amanda,Garza, Liliana,Adeosun, Samuel
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- TRIMETHYLSILYLFLUOROSULFONATE (TMSOFs): AN ALTERNATIVE TO TMS TRIFLATE AS A SOURCE OF Me3Si+
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Generation of trimethylsilylfluorosulfonate in situ provides a useful source of TMS+, the reactivity of which is essentially equivalent to that of TMS triflate.Its precursors, in particular FSO3H, are less costly than those of TMSOTf or the reagent itself.
- Lipshutz, Bruce H.,Burgess-Henry, Jana,Roth, Gregory P.
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- Substituent and Temperature Effects on the Reactions of Benzylchlorocarbene with Alcohol
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The insertion reaction of the para-substituted benzylchlorocarbenes with methanol shows a second-order dependence in methanol, but only a first-order dependence in ethylene glycol.The results are consistent with a mechanism whereby the carbene inserts into the O-H bond of the alcohol dimer or oligomer by electrophilic attack of the carbene on the oxigenone pair to produce a reversibly formed ylide intermediate.The effects of the substituents indicate that electron-releasing group favours rearrangement while electron-withdrawing group facilitates insertion.Photolysis of halogenodiazirines in methanol at low temperatures give rise to V-shaped Arrhenius behaviour and the importance of N2 in influencing the reactivity of the singlet halogenocarbene in the matrix is demonstrated.
- Liu, Michael T. H.,Subramanian, Ramasamy
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- Method for the selective formation of dimethyl acetals in the presence of hydroxylamine
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An inexpensive and mild method for the formation of dimethyl acetals from the corresponding aldehydes is achieved using hydroxylamine and methanol under neutral conditions at room temperature. Notably, the reaction is selective for aldehydes in the presence of ketones, rendering this an example of a chemoselective acetalization. For saturated, sterically accessible aldehydes, catalytic amounts of hydroxylamine may be employed to attain the corresponding dimethyl acetal as the sole product in good to excellent yield. Unsaturated and hindered aldehydes required stoichiometric amounts of hydroxylamine but provided dimethyl acetals as the major product in typically excellent yield. In some cases, the corresponding oxime was also observed but may be separated from the acetal by flash column chromatography or distillation. The involvement of an intermediate oxime compound is postulated. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications to view the free supplemental file. Taylor & Francis Group, LLC.
- Mickelsen, Ky J.,Tajc, Chelsea M.,Greenwood, Kevin R.,Browder, Cindy C.
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- Lewis Base Catalyzed Dioxygenation of Olefins with Hypervalent Iodine Reagents
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1,2-Diols are extremely useful building blocks in organic synthesis. Hypervalent iodine reagents are useful for the vicinal dihydroxylation of olefins to give 1,2-diols under metal-free conditions, but strongly acidic promoters are often required. Herein, we report a catalytic vicinal dioxygenation of olefins with hypervalent iodine reagents using Lewis bases as catalysts. The conditions are mild and compatible with various functional groups.
- Pan, Liangkun,Ke, Zhihai,Yeung, Ying-Yeung
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supporting information
p. 8174 - 8178
(2021/10/25)
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- Electrochemical oxidative decarboxylation and 1,2-aryl migration towards the synthesis of 1,2-diaryl ethers
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Carboxylic acid compounds are important chemicals and are widely present in various natural products. They are not only nucleophiles, but also radical precursors. Classic transition-metal-catalyzed and photochemical decarboxylation have shown their excellent site selectivity in radical chemistry. However, electrochemical decarboxylation with a long history hasn't got enough attention in recent years. In this work, the electrochemical oxidative decarboxylation and 1,2-aryl migration of 3,3-diarylpropionic acids have been introduced to construct C-O bonds with alcohols. Remarkably, this transformation can proceed smoothly without metal catalysts and external oxidants.
- Bu, Faxiang,Hu, Xia,Lei, Aiwen,Lu, Lijun,Wang, Shengchun,Zhang, Heng
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p. 10000 - 10004
(2020/10/06)
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- Two-way homologation of aliphatic aldehydes: Both one-carbon shortening and lengthening via the same intermediate
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Aliphatic aldehydes can be homologated to both one-carbon shorter and one-carbon longer homologous carbonyl compounds through the 2–4 steps of reactions via the same intermediates, β,γ-unsaturated α-nitrosulfones, prepared from the proline-catalyzed sequential reactions of several aliphatic aldehydes with phenylsulfonylnitromethane. While the oxidative cleavage of the key intermediates gave one-carbon less homologous carbonyl compounds, the reduction of the same key intermediates followed by an oxidation produced one-carbon more homologous carbonyl compounds.
- Yoo, Jae Won,Seo, Youngran,Park, Jong Beom,Kim, Young Gyu
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- Nickel-Catalyzed Chemoselective Acetalization of Aldehydes With Alcohols under Neutral Conditions
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A molecularly defined NiII-complex catalyzing the chemoselective acetalization of aldehydes with alcohols under neutral conditions is reported. The reaction is general, efficient and showed a wide substrate scope (including aliphatic aldehydes) as well as excellent functional group tolerance. Reusability of the present nickel catalyst is also demonstrated.
- Subaramanian, Murugan,Landge, Vinod G.,Mondal, Akash,Gupta, Virendrakumar,Balaraman, Ekambaram
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supporting information
p. 4557 - 4562
(2019/08/30)
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- House bulb light-induced photochemical acetalization of carbonyl compounds catalyzed by Eosin Y
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We have systematically studied the reactions of acetalization and found that high reaction efficiency can be achieved using cheap and readily available organic Eosin Y as catalyst. The reaction proceeds smoothly under house bulbs and shows excellent functional group tolerance. The substrates of the reaction system are compatible with aromatic aldehydes, aliphatic aldehydes, aromatic ketones, and cyclic ketones with high yields.
- Zhou, Quan,Jia, Tao,Li, Xiao-Xuan,Zhou, Lin,Li, Chang-Jiang,Feng, Yi-Si
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supporting information
p. 1068 - 1075
(2018/05/23)
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- Cleavage of the lignin β-O-4 ether bond: Via a dehydroxylation-hydrogenation strategy over a NiMo sulfide catalyst
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The efficient cleavage of lignin β-O-4 ether bonds to produce aromatics is a challenging and attractive topic. Recently a growing number of studies have revealed that the initial oxidation of CαHOH to CαO can decrease the β-O-4 bond dissociation energy (BDE) from 274.0 kJ mol-1 to 227.8 kJ mol-1, and thus the β-O-4 bond is more readily cleaved in the subsequent transfer hydrogenation, or acidolysis. Here we show that the first reaction step, except in the above-mentioned pre-oxidation methods, can be a Cα-OH bond dehydroxylation to form a radical intermediate on the acid-redox site of a NiMo sulfide catalyst. The formation of a Cα radical greatly decreases the Cβ-OPh BDE from 274.0 kJ mol-1 to 66.9 kJ mol-1 thereby facilitating its cleavage to styrene, phenols and ethers with H2 and an alcohol solvent. This is supported by control experiments using several reaction intermediates as reactants, analysis of product generation and by radical trap with TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) as well as by density functional theory (DFT) calculations. The dehydroxylation-hydrogenation reaction is conducted under non-oxidative conditions, which are beneficial for stabilizing phenol products.
- Zhang, Chaofeng,Lu, Jianmin,Zhang, Xiaochen,Macarthur, Katherine,Heggen, Marc,Li, Hongji,Wang, Feng
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supporting information
p. 6545 - 6555
(2018/06/06)
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- Green synthesis method of acetal-type or ketal-type compound
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The invention discloses a green synthesis method of an acetal-type or ketal-type compound. A carbonyl compound is used as a raw material, a hydrogen-loaded compound is used as a catalyst, then an alcohol substance is added, a reaction is performed to generate the acetal-type or ketal-type compound. The synthesis method is simple and convenient, is high in conversion rate and yield, is safe and stable, has low toxicity and is easy to operate; the used catalyst is simple to prepare, and is cheap and easy to obtain; the reaction process is mild and efficient; the product is easy to separate and purify; the green synthesis method has a wide substrate application range, can be used for synthesizing acetal and ketal spices, and has potential industrial application value.
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Paragraph 0057-0062
(2017/05/26)
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- Catalysed anti-Markovnikov oxidation of terminal aryl alkenes to aldehydes and transformation of methyl aryl tertiary amines to formamides with H2O2 as a terminal oxidant
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Anti-Markovnikov oxidation of terminal aryl alkenes to aldehydes and transformation of N-methyl aryl tertiary amines to formamides with H2O2 as a terminal oxidant under mild conditions have been achieved with moderate to good product yields using [FeIII(TF4DMAP)OTf] as catalyst. This journal is
- Du, Yi-Dan,Tse, Chun-Wai,Xu, Zhen-Jiang,Liu, Yungen,Che, Chi-Ming
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supporting information
p. 12669 - 12672
(2015/05/20)
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- A generalized approach for iron catalyzed chemo- and regioselective formation of anti-Markovnikov acetals from styrene derivatives
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Fe(BF4)2·6H2O in the presence of pyridine-2,6-dicarboxylic acid and PhI(OAc)2 can efficiently catalyze the formation of chemoselective dialkyl acetals from styrene derivatives with anti-Markovnikov regioselectivity in good to high yields under mild and benign reaction conditions.
- Chowdhury, Abhishek Dutta,Lahiri, Goutam Kumar
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supporting information; experimental part
p. 3448 - 3450
(2012/05/20)
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- Rhodium-catalyzed anti-Markovnikov intermolecular hydroalkoxylation of terminal acetylenes
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We report here the first transition-metal-catalyzed anti-Markovnikov intermolecular hydroalkoxylation of terminal acetylenes to give enol ethers in high yields without using bases. Arylacetylenes as well as alkenyl- and alkylacetylenes were coupled with aliphatic alcohols, and the products were obtained with high Z selectivity in most cases. Effective catalysts were 8-quinolinolato rhodium complexes, which are structurally simple but have been relatively unexplored as catalysts.
- Kondo, Masataka,Kochi, Takuya,Kakiuchi, Fumitoshi
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scheme or table
p. 32 - 34
(2011/03/16)
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- Polymer-supported α-aminonitriles: Alkylation reactions and carbonyl compound cleavage
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A polystyrene-supported α-aminonitrile has been prepared and its successive mono- and dialkylations achieved. Complementary procedures allow cleavage of the alkylated moities in either carbonyl or acetal form. Georg Thieme Verlag Stuttgart - New York.
- Beaufort-Droal, Virginie,Pereira, Elisabeth,Vergne, Fabrice,Aitken, David J.
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experimental part
p. 2913 - 2917
(2011/02/25)
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- Metal organic frameworks as solid acid catalysts for acetalization of aldehydes with methanol
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Room temperature acetalization of aldehydes with methanol has been carried out using metal organic frameworks (MOFs) as solid heterogeneous catalysts. Of the MOFs tested, a copper-containing MOF [Cu3(BTC)2] (BTC=1,3,5-benzenetricarboxylate) showed better catalytic activity than an iron-containing MOF [Fe(BTC)] and an aluminium containing MOF [Al 2(BDC)3] (BDC=1,4-benzenedicarboxylate). The protocol was validated for a series of aromatic and aliphatic aldehydes and used to protect various aldehydes into commercially important acetals in good yields without the need of water removal. In addition, the reusability and heterogeneity of this catalytic system was demonstrated. The structural stability of MOF was further studied by characterization with powder X-ray diffraction, Brunauer-Emmett- Teller surface area measurements and Fourier-transformed infrared spectroscopic analysis of a deactivated catalyst used to convert a large amount of benzaldehyde. The performance of copper MOF as acetalization catalyst compares favourably with those of other conventional homogeneous and heterogeneous catalysts such as zinc chloride, zeolite and clay. Copyright
- Dhakshinamoorthy, Amarajothi,Alvaro, Mercedes,Garcia, Hermenegildo
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scheme or table
p. 3022 - 3030
(2011/02/24)
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- o-benzenedisulfonimide as reusable bronsted acid catalyst for acid-catalyzed organic reactions
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Acid-catalyzed organic reactions, such as etherification, esterification, acetal synthesis, cleavage, and interconversion, and pinacol rearrangement were carried out in the presence of catalytic amounts of o-benzenedisulfonimide as Bronsted acid catalyst; the conditions were mild and selective. The catalyst was easily recovered and purified, ready to be used in further reactions, with economic and ecological advantages. Georg Thieme Verlag Stuttgart.
- Barbero, Margherita,Cadamuro, Silvano,Dughera, Stefano,Venturello, Paolo
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p. 1379 - 1388
(2008/12/21)
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- Efficient addition of alcohols, amines and phenol to unactivated alkenes by AuIII or PdII stabilized by CuCl2
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The nucleophilic addition of alcohols, amines and phenol to unactivated alkenes catalyzed by cationic gold and palladium becomes limited due to the fast reduction into metallic gold under reaction conditions. The presence of CuCl2 retards the reduction of AuIII and PdII, strongly increasing the turnover number of gold and palladium catalysts. It is shown that new AuIII-CuCl2 and PdII-CuCl 2 catalysts are active and selective for the nucleophilic addition of alcohols, amines and phenol to unactivated alkenes. This journal is The Royal Society of Chemistry.
- Zhang, Xin,Corma, Avelino
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p. 397 - 403
(2008/09/17)
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- Indium(III)trifluoromethanesulfonate as a mild, efficient catalyst for the formation of acetals and ketals in the presence of acid sensitive functional groups
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Aldehydes and ketones, including acetophenone and benzophenone, are readily protected under mild, neutral conditions in the presence of various alcohols or orthoformates and catalytic amounts of indium(III) trifluoromethanesulfonate (0.8 mol %) under either room temperature or mild heating conditions to give the corresponding cyclic and acyclic acetals and ketals in good to excellent yields. Acid sensitive functional groups, N-Boc, THP, and TBDMS do not undergo competitive deprotection under the reported conditions.
- Gregg, Brian T.,Golden, Kathryn C.,Quinn, John F.
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p. 3287 - 3295
(2008/09/21)
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- Effective Au(III)-CuCl2-catalyzed addition of alcohols to alkenes
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Alkenes can be activated by Au(III) catalysts, and the effective addition of alcohols to alkenes can be carried out under mild conditions with Au(III), provided that catalytic amounts of CuCl2 are added, which significantly stabilize the cationic Au(III). The Royal Society of Chemistry.
- Zhang, Xin,Corma, Avelino
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p. 3080 - 3082
(2008/02/10)
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- IPy2BF4-mediated rearrangements of 1,2-difunctionalized compounds and olefins
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Acetal derivatives are easily obtained from 1,2-difunctionalized compounds by a new reaction mediated by IPy2BF4 with a mechanism based on a 1,2-migration of aryl or alkyl groups. A new oxidative rearrangement reaction of olefins is also described. Moreover, when this metal-free protocol is applied to cyclic olefins, interesting ring-contraction reactions are observed. The new methodologies described here are a clean and efficient alternative to known strategies that make use of potentially toxic metallic complexes.
- Fananas, Francisco J.,Alvarez-Perez, Monica,Rodriguez, Felix
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p. 5938 - 5944
(2007/10/03)
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- Copper(II) tetrafluoroborate as a novel and highly efficient catalyst for acetal formation
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Commercially available copper(II) tetrafluoroborate hydrate has been found to be a highly efficient catalyst for dimethyl/diethyl acetal formation in high yields from aldehydes and ketones by reaction with trimethyl/triethyl orthoformate at room temperature and in short period. Acetalisation was carried out under solvent-free conditions with electrophilic aldehydes/ketones. For weakly electrophilic aldehydes/ketones (e.g., benzaldehyde, cinnamaldehyde and acetophenone) and for aldehydes having a substituent that can coordinate with the catalyst, the corresponding alcohol was used as solvent.
- Kumar, Raj,Chakraborti, Asit K.
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p. 8319 - 8323
(2007/10/03)
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- Photochemical acetalization of carbonyl compounds in protic media using an in situ generated photocatalyst
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Carbonyl compounds are conveniently converted into their corresponding dimethyl acetals in good yields and short reaction times by means of a photochemical reaction in methanol with a catalytic amount of chloranil (2,3,5,6-tetrachloro-1,4-benzoquinone, CA) as the sensitizer. Using aldehydes gives better results than using ketones, which also tend to form enol ethers as side products. These results are similar to those of simple acid-catalyzed acetalization reactions, suggesting the involvement of a photochemically generated acid. On the basis of steady state and laser flash photolysis data the reaction is proposed to involve the in situ generation of a photocatalyst (2,3,5,6-tetrachloro-1,4-hydroquinone, TCHQ) via reaction of CA with the solvent. The acetalization process is initiated by ionization of TCHQ, followed by loss of a proton to the solvent or the carbonyl, which starts a catalytic reaction. The photocatalyst is regenerated via a disproportionation reaction.
- De Lijser, H.J. Peter,Rangel, Natalie Ann
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p. 8315 - 8322
(2007/10/03)
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- New oxidative transformations of alkenes and alkynes under the action of diacetoxyiodobenzene
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Treatment of alkenes and alkynes with diacetoxyiodobenzene activated by mineral and organic acids predominantly results in oxidative rearrangement. 1,4-Diphenylbutadiene in MeOH gives 3,4-dimethoxy-1,4-diphenylbut-1-ene.
- Yusubov,Zholobova,Filimonova,Chi, Ki-Whan
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p. 1735 - 1742
(2007/10/03)
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- Isolation, Characterization, and Reaction of Activated Iodosylbenzene Monomer Hydroxy(phenyl)iodonium Ion with Hypervalent Bonding: Supramolecular Complex PhI+OH·18-Crown-6 with Secondary I...O Interactions
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The isolation, characterization, and reaction of the active species hydroxy(phenyl)iodonium ion with hypervalent bonding are reported. Reaction of iodosylbenzene with HBF4-Me2O in the presence of equimolar 18-crown-6 in dichloromethane afforded the hydroxy-λ3-iodane complex PhI(OH)BF4·18-crown-6 as stable yellow prisms. X-ray structure analysis indicated that both the close contacts between the iodine(III) and the three adjacent oxygen atoms of 18-crown-6, and the hydrogen bonding OH...O(crown ether) will be responsible for the increased stability of the complex as compared to the uncomplexed PhI(OH)BF4. The crown ether complex is highly reactive and serves as a versatile oxidant even in water: thus, the complex undergoes oxidative transformations of a variety of functional groups such as olefins, alkynes, enones, silyl enol ethers, sulfides, and phenols under mild conditions. Copyright
- Ochiai, Masahito,Miyamoto, Kazunori,Shiro, Motoo,Ozawa, Tomoyuki,Yamaguchi, Kentaro
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p. 13006 - 13007
(2007/10/05)
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- Solvolysis of styryliodonium salt: Products, rates, and mechanisms
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The solvolysis of phenyl[(E)-styryl]iodonium tetrafluoroborate in various solvents was examined at 50-70°C by means of product and kinetic studies with the normal and labeled substrates. The reactions involved are α-elimination and substitutions with configurational retention and inversion. In methanol and ethanol, the main reaction is α-elimination, along with about 5% of substitution with the ratio of inversion/retention from 4/6 to 3/7. As the basicity of the solvent decreases, the reaction rate and the fraction of α-elimination decrease, and at the same time the ratio of inversion/retention of substitution also decreases. In 2,2,2- trifluoroethanol, only the substitution with retention was observed. Labeling experiments showed that complete isotope scrambling occurred between the olefinic hydrogens of the retained product while the deuterium remained at the original position of the inverted product. The substitution mechanism is concluded to involve parallel pathways: an S(N) 1-type with a vinylenebenzenium ion intermediate leading to retention and a vinylic S(N) 2- type with a direct attack by the nucleophilic solvent leading to inversion.
- Okuyama, Tadashi,Ishida, Yoshimi,Ochiai, Masahito
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p. 163 - 170
(2007/10/03)
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- Regioselective addition of alcohols to internal 1-aryl-1-alkynes catalyzed by a triangular heterobimetallic Ir2Pd sulfido cluster
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The triangular heterobimetallic sulfido cluster [(Cp*Ir)2(μ3-S)2PdCl2] prepared from [PdCl2(cod)] and [Cp*IrCl(μ-SH)2IrCp*Cl] was found to catalyze the addition of alcohols to alkynes to give the corresponding ketals. In particular, internal 1-aryl-1-alkynes were transformed into the corresponding 2,2-dialkoxy-1-arylalkanes with high regioselectivity. The analogous Ir2PtS2 cluster proved to be much less selective.
- Masui, Dai,Ishii, Youichi,Hidai, Masanobu
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p. 717 - 718
(2007/10/03)
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- A simple one-pot procedure for the conversion of aldehydes to methyl esters
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Several methyl esters were obtained by an efficient and simple one-pot procedure from the corresponding aldehydes in high yields. This procedure involves dimethyl acetal formation from aldehydes and subsequent oxidation.
- Rhee, Hakjune,Kim, Jin Yeon
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p. 1365 - 1368
(2007/10/03)
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- Total synthesis of isodeoxypodophyllotoxin using the Me3Sn radical initiated carbocyclization
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The lactone portion of the podophylotoxin framework was assembled from a free-radical carbocyclization reaction, and the target structure was constructed based on intramolecular Friedel-Crafts reaction. In addition to isodeoxypodophyllotoxin, there were formed unusual tri- and tetracyclic compounds.The lactone portion of the podophylotoxin framework was assembled from a free-radical carbocyclization reaction, and the target structure was constructed based on intramolecular Friedel-Crafts reaction. In addition to isodeoxypodophyllotoxin, there were formed unusual tri- and tetracyclic compounds.
- Hanessian, Stephen,Ninkovic, Sacha
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p. 1880 - 1888
(2007/10/03)
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- Oxidation of Some Olefinic Compounds using Iodosobenzene
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Oxidation of dihydropyran, cyclohexene and styrene with iodosobenzene under suitable conditions leads to rearranged products; dihydrofuran gives addition products in this oxidation process.
- Moriarty, Robert M.,Prakash, Om,Duncan, Michael P.,Vaid, Rahde K.,Rani, Neena
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p. 432 - 433
(2007/10/03)
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- NUCLEOPHILIC ADDITION TO ALKYNES IN SUPERBASIC CATALYTIC SYSTEMS. IV. VINYLATION OF ALCOHOLS BY PHENYLACETYLENE. A PATH TO PHENYLACETALDEHYDE AND ITS ACETALS
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A method is proposed for the synthesis of phenylacetaldehyde, involving nucleophilic addition of methanol to phenylacetylene in the potassium hydroxide-DMSO system followed by acid-catalyzed hydrolysis of the obtained methyl styryl ether.Electrophilic addition of alcohols and glycerol to the latter in the presence of p-toluenesulfonic acid leads to high yields of the corresponding acetals of phenylacetaldehyde.
- Tarasova, O. A.,Mikhailova, A. I.,Shmidt, E. Yu.,Polovnikova, R. I.,Trofimov, B. A.
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p. 860 - 862
(2007/10/02)
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- Process for the preparation of arylacetaldehyde-dialkylacetals
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Arylacetaldehyde-dialkylacetals are prepared with high yields and selectivity from the corresponding chloromethylaromatics in the presence of hydrogen chloride acceptors and methyl carbonyl compounds as catalysts and in the presence of orthoesters as water-binding agents by hydroformylation with carbon monoxide and hydrogen.
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- Antipsoriatic Anthrones with Modulated Redox Properties. 1. Novel 10-Substituted 1,8-Dihydroxy-9(10H)-anthracenones as Inhibitors of 5-Lipoxygenase
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The syntheses, the biological evaluation, and the structure-activity relationships of a novel series of 1,8-dihydroxy-9(10H)-anthracenones bearing acyl-, alkyl-, or alkylidene-linked aromatic substituents in the 10-position are described.The phenylacyl and phenylalkylidene analogs were far more potent inhibitors of 5-lipoxygenase (5-LO) from bovine polymorphonuclear leukocytes (IC50 values in the 10-7 M range) than the antipsoriatic drug anthralin, whereas phenylalkyl analogs were only weak inhibitors.Among the active compounds were both potent generators of hydroxyl radicals, as determined by deoxyribose degradation, and strong reducers of the stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH).However, several derivatives of this series maintained 5-LO inhibitory activity but did not generate hydroxyl radicals and were not reactive with DPPH.In particular, phenylacyl analogs were also 6 times more efficient in inhibition of lipid peroxidation in model membranes than anthralin.Structure-activity relationships have shown that the presence of free phenolic groups in the attached aromatic ring is beneficial but not required for 5-LO inhibitory potency.The inhibitory potency in the 10-phenylacyl series increased with the length of the acyl chain with three methylene units being the optimum, suggesting a specific enzyme interaction which would not be expected for nonspecific redox inhibitors.
- Mueller, Klaus,Guerster, Dieter,Piwek, Susanne,Wiegrebe, Wolfgang
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p. 4099 - 4107
(2007/10/02)
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- BROMINATION OF DIMETHYLACETALS WITH Br2-CHLOROTRIMETHYLSILANE-NaBr
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α-Bromodimethylacetals are obtained in excellent yields by treating dimethylacetals with Br2-NaBr-chlorotrimethylsilane in CH3OH/CH3CN (2:1). The method is suitable for large scale preparation.
- Bellesia, Franco,Boni, Monica,Ghelfi, Franco,Pagnoni, Ugo Maria
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p. 629 - 632
(2007/10/02)
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- (Benzotriazol-1-yl)methoxymethyl anion: A novel methylal anion equivalent
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The title anion readily reacts with a variety of electrophiles to give adducts which, upon treatment with methanol in the presence of p-toluenesulfonic acid, afford the corresponding α-functionalized dimethyl acetals.
- Katritzky,Yang,Cundy
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p. 3061 - 3071
(2007/10/02)
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- Copper-Mediated Oxygenation of Aldehydes and Internal Cannizzaro-like Rearrangement of Phenylglyoxal
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Under the influence of Cu(II) in MeOH containing py and Et3N, PhCH2CHO undergoes competitive O2-dependent conversions to PhCHO and phenylglyoxal.The latter, as the MeOH hemiacetal, undergoes a Cu(II)-catalyzed rearrangement to PhCHOHCOOMe and a Cu(II) oxidation to PhCOCOOMe, and there appears to be independent O2-mediated production of PhCOCOOH.Phenylglyoxal also undergoes oxidative cleavage to PhCOOH, but does not give rise to PhCHO.The homologous aldehyde PhCH2CH2CHO is converted mainly via PhCH2CHO to a product mixture derived from the latter.This result is interp reted in terms of preferential C-C cleavage of an α-hydroxyperoxide intermediate initially formed from PhCH2CH2CHO.The alternative pathway for this intermediate, dehydration to α-keto aldehyde PhCH2COCHO, is barely competitive, because the independently prepared α-keto aldehyde gives a distinct set of products under the reaction conditions.The preference for cleavage over dehydration explains the previously published finding of a stepwise degradation of long-chain aldehydes to formate units by the Cu(II)-py-Et3N-MeOH-O2 system.Product comparisons using either an O2 atmosphere or a N2 atmosphere (with varying equivalents of CuII) permit a distinction between stoichiometric Cu(II) oxidations and O2-dependent reactions.Mechanism are proposed for the observed transformations.
- Jin, Shiow-Jen,Arora, Pramod K.,Sayre, Lawrence M.
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p. 3011 - 3018
(2007/10/02)
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- ELECTROOXIDATIVE REARRANGEMENT OF CONJUGATED ARYLOLEFINS TO ARYLACETALDEHYDE DIMETHYL ACETALS
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Electrochemical oxidation of conjugated arylolefins 1 in trimethyl orthoformate containing iodine gave arylacetaldehyde dimethyl acetals 2 in high yields.
- Shono, Tatsuya,Matsumura, Yoshihiro,Katoh, Susumu,Ikeda, Kaoru,Fujita, Tetsuhiro,Kamada, Tohru
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p. 5309 - 5312
(2007/10/02)
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- Metalation of Alkynes. Part 2. Behaviour of Alkynes with Mercury(II)Acetate in Methanol: a Systematic Reinvestigation
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The reaction of a series of alkynes with mercury(II)acetate, both in equimolar and catalytic amounts, were investigated in methanol.Hex-1-yne, oct-1-yne, oct-4-yne, 1,4-diacetoxybut-2-yne, methyl oct-2-ynoate, methyl 3-phenylpropynoate, oct-2-ynoic acid, phenylpropynoic acid, oct-1-yn-3-ol, 1-ethynylcyclohexanol, 1-ethynylcyclohexamine, phenylethyne, diphenylethyne, and ethynylferrocene were the examined substrates.The non-mercuriated products from the reaction were the corresponding vinyl ether, dialkoxyalkane, and ketone, isolated under preparative conditions.The presence of 0.1percent toluene-p-sulphonic acid increased the reactivity.The reactions of oct-1-yne and oct-4-yne were studied in detail by following with time the formation of the products under a variety of conditions, and a mechanistic scheme was drawn.For comparison, styrene, trans-oct-4-ene, and trans-β-methylstyrene were treated with 5 molpercent mercury(II) acetate.The reaction of alkenes was found to be non-catalytic.
- Bassetti, Mauro,Floris, Barbara
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p. 227 - 234
(2007/10/02)
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- Effect of Diazirine Concentration on the Reaction of 3-Benzyl-3-chlorodiazirine with Methanol
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In the reation of 3-chloro-3-benzyldiazirine with methanol, the concentration of diazirine has pronounced effects on the acetal/chlorostyrene product ratio.A mechanism is proposed to account for these results.
- Liu, Michael T. H.,Subramanian, Ramasamy
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- CONVERSION OF ALKYL PHENYL SELENIDES AND SELENOXIDES INTO DIALKYL ETHERS. NUCLEOFUGACITY ENHANCEMENT OF THE PLENYLSELENINYL GROUP BY meta-CHLOROPERBENZOIC ACID IN ALCOHOLS
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The recently reported conversion of alkyl phenyl selenides into dialkyl ethers, promoted by MCPBA in alcohols, has been reinvestigated.It is concluded that the reactive intermediate does not derive from the selenones, as reported, but from the selenoxides.It is suggested that MCPBA adds to the selenoxide function to give an intermediate which easily gives rise to solvolysis; thus, the addition of MCPBA greatly enhances the nucleofugacity of the phenylseleninyl group.The synthesis and the reactivity of several 1-phenyl, 2-phenylseleninyl- and 1-phenyl-, 2-phenylselenonyl-ethanes are also described.
- Tiecco, Marcello,Testaferri, Lorenzo,Tingoli, Marco,Chianelli, Donatella,Bartoli, Donatella
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p. 423 - 428
(2007/10/02)
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- Electrochemical Oxidation of (S)-Malic-Acid Derivatives: a Route to Enantiomerically Pure Alkylmalonaldehydic Esters
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The 3,3-dialkylmalic-acid diesters, prepared by the previously described diastereoselective alkylations through dilithium alkoxide enolates, are saponified to the monoesters containing a free α-hydroxycarboxylic-acid moiety.The monoesters are subjected to electrochemical oxidative decarboxylation in MeOH.If the intermediate monoacids are purified, the malonaldehydic esters (2-formyl-2-alkoxycarboxylates) obtained by this procedure are enantiomerically pure; they have the same structural features, i.e. two enantiotopic functionalized branches on the (persubstituted) stereogenic center, as the well known 3-hydroxy-2-methylpropanoic acid ('Roche acid') which was employed frequently as a starting material for the preparation of either enantiomer of various target molecules.
- Renaud, Philippe,Muerzeler, Marianne,Seebach, Dieter
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p. 292 - 298
(2007/10/02)
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