- Generation of Aryllithium Reagents from N -Arylpyrroles Using Lithium
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Treatment of 1-aryl-2,5-diphenylpyrroles with lithium powder in tetrahydrofuran at 0 °C results in the generation of the corresponding aryllithium reagents through reductive C-N bond cleavage.
- Ozaki, Tomoya,Kaga, Atsushi,Saito, Hayate,Yorimitsu, Hideki
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p. 3019 - 3028
(2021/06/02)
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- Cascade Synthesis of Pyrroles from Nitroarenes with Benign Reductants Using a Heterogeneous Cobalt Catalyst
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A bifunctional 3d-metal catalyst for the cascade synthesis of diverse pyrroles from nitroarenes is presented. The optimal catalytic system Co/NGr-C@SiO2-L is obtained by pyrolysis of a cobalt-impregnated composite followed by subsequent selective leaching. In the presence of this material, (transfer) hydrogenation of easily available nitroarenes and subsequent Paal–Knorr/Clauson-Kass condensation provides >40 pyrroles in good to high yields using dihydrogen, formic acid, or a CO/H2O mixture (WGSR conditions) as reductant. In addition to the favorable step economy, this straightforward domino process does not require any solvents or external co-catalysts. The general synthetic utility of this methodology was demonstrated on a variety of functionalized substrates including the preparation of biologically active and pharmaceutically relevant compounds, for example, (+)-Isamoltane.
- Ryabchuk, Pavel,Leischner, Thomas,Kreyenschulte, Carsten,Spannenberg, Anke,Junge, Kathrin,Beller, Matthias
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supporting information
p. 18679 - 18685
(2020/09/02)
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- Copper-catalyzed pyrrole synthesis from 3,6-dihydro-1,2-oxazines
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Highly-functionalized pyrroles could be effectively synthesized from 3,6-dihydro-1,2-oxazines using a heterogeneous copper on carbon (Cu/C) under neat heating conditions. Furthermore, the in situ formation of 3,6-dihydro-1,2-oxazines via the hetero Diels-Alder reaction between nitroso dienophiles and 1,3-dienes and the following Cu/C-catalyzed pyrrole synthesis also provided the corresponding pyrrole derivatives in a one-pot manner.
- Yasukawa, Naoki,Kuwata, Marina,Imai, Takuya,Monguchi, Yasunari,Sajiki, Hironao,Sawama, Yoshinari
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supporting information
p. 4409 - 4413
(2018/10/17)
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- Copper(II)-Promoted, One-Pot Conversion of 1-Alkynes with Anhydrides or Primary Amines to the Respective 2,5-Disubstituted Furans or Pyrroles under Microwave Irradiation Conditions
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Furans and pyrroles are prepared from 1-alkynes by using a Cu(II)-promoted, one-pot, microwave irradiation method. Glaser coupling of 1-alkynes and cyclization of the resulting 1,3-diyne in the presence of an anhydride or a primary amine results in the formation of the respective 2,5-diaryl- or 2,5-dialkyl-substituted furans and pyrroles.
- Lee, Hyejeong,Yi, Yeonhui,Jun, Chul-Ho
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supporting information
p. 3485 - 3490
(2016/01/25)
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- s-Block-Metal-Mediated Hydroamination of Diphenylbutadiyne with Primary Arylamines Using a Dipotassium Tetrakis(amino)calciate Precatalyst
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(Chemical Equation Presented). The hydroamination of diphenylbutadiyne with primary arylamines requires a reactive catalyst. In the presence of heterobimetallic K2[Ca{N(H)Dipp}4] (Dipp = 2,6-diisopropylphenyl) the performance of this
- Younis, Fadi M.,Krieck, Sven,G?rls, Helmar,Westerhausen, Matthias
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supporting information
p. 3577 - 3585
(2015/08/06)
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- A general approach to arylated furans, pyrroles, and thiophenes
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A general and practical synthetic method for aryl-substituted five-membered heterocycles has been developed. In the presence of KOH (30%), 1,4-diaryl-1,3-butadiynes undergo the cyclocondensation reaction with water, primary amines, and Na2S·9H2O in DMSO at 80 °C to afford 2,5-diarylfurans, 1,2,5-trisubstituted pyrroles, and 2,5-diarylthiophenes in good to high yields. Further studies have disclosed that aryl-substituted five-membered heterocycles can be also synthesized by a one-pot, two-step strategy from the terminal alkynes in DMSO firstly catalyzed by CuCl, and then via addition of KOH to promote the cyclocondensation of 1,3-butadiynes generated in situ.
- Zheng, Qingwei,Hua, Ruimao,Jiang, Jianhua,Zhang, Lei
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p. 8252 - 8256
(2015/03/05)
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- Organic synthesis in deep eutectic solvents: Paal-Knorr reactions
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Deep eutectic solvents (the combination of either urea or glycerol with choline chloride) are effective solvents/catalysts for Paal-Knorr reactions to form pyrroles of furans. The reaction conditions are quite mild and do not require the addition of an additional Bronsted or Lewis acid catalyst. Given the inexpensive, non-toxic, and recyclable nature of the DES, these reaction conditions are simple and highly environmentally friendly.
- Handy, Scott,Lavender, Kevin
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supporting information
p. 4377 - 4379
(2013/07/26)
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- Synthesis of 2,5-diarylpyrroles by ligand-free palladium-catalyzed ch activation of pyrroles in ionic liquids
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The palladium-catalyzed CH activation and arylation of N-methylpyrrole and N-phenylpyrrole allowed a convenient synthesis of diarylpyrroles. The reactions were performed by using tetrabutylammonium acetate as an ionic solvent, which allowed for the application of a ligand-free catalytic system by using simple palladium salts or polyvinylpyrrolidone-stabilized palladium nanoparticles as the catalyst.
- Ehlers, Peter,Petrosyan, Andranik,Baumgard, Jens,Jopp, Stefan,Steinfeld, Norbert,Ghochikyan, Tariel V.,Saghyan, Ashot S.,Fischer, Christine,Langer, Peter
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p. 2504 - 2511
(2013/08/23)
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- Xanthan sulfuric acid as an efficient, green, biodegradable, and recyclable solid acid catalyst for one-pot synthesis of N-substituted pyrroles under solvent-free conditions at room temperature
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A new, green, and efficient method for synthesis of a variety of N-substituted pyrroles from condensation reactions of 2,5-hexanedione with amines or diamines using xanthan sulfuric acid as a biosupported and reusable ecofriendly catalyst under solvent-free conditions at room temperature is described. The use of a nontoxic, inexpensive, easily available, and reusable biosupported proton source catalyst under solvent-free conditions makes this protocol practical, environmentally friendly, and economically attractive.
- Rahmatpour, Ali
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experimental part
p. 491 - 495
(2012/06/16)
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- Polystyrene-supported GaCl3 as a highly efficient and recyclable heterogeneous Lewis acid catalyst for one-pot synthesis of N-substituted pyrroles
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A new and environmentally benign method for the preparation of N-substituted pyrroles from one-pot condensation reaction of 2,5-hexanedione with amines and diamines in the presence of polystyrene-supported gallium trichloride (PS/GaCl3) as a highly active and reusable heterogeneous Lewis acid catalyst is presented. This new protocol has the advantages of easy availability, stability, reusability and eco-friendly of the catalyst, high to excellent yields, simple experimental and work-up procedure.
- Rahmatpour, Ali
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experimental part
p. 15 - 19
(2012/07/03)
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- An efficient procedure for the synthesis of polysubstituted pyrroles in an ionic liquid
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The ionic liquid 1-butyl-3-methyl-imidazolium hydrogen sulfate, [bmim]HSO4, was used as a catalyst and reaction medium for the pyrrole synthesis, and a wide range of aliphatic, aromatic, heteroaromatic and carboxylic 1,4-diketones easily underwent condensations with aniline and ethylenediamine to form polysubstituted pyrroles. Sequential decarboxylation/Paal-Knorr pyrrole condensation was observed, which provides a new and facile approach to monoester pyrroles from 1,4-diketo-2,3-dicarboxylic acid esters.
- He, Yan-Hong,Wang, Gang-Qiang,Xu, Ke-Ling,Guan, Zhi
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experimental part
p. 191 - 196
(2011/05/07)
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- N-substituted pyrrole synthesis by Paal-Knorr condensation using recyclable cationic exchange resin in water
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(Chemical Equation Presented) Cationic exchange resin has been utilized for the first time as a novel and recyclable heterogeneous catalyst for the synthesis of N-substituted pyrroles from variety of 1,4-diketones and aniline. This simple synthesis has been accomplished with excellent yields. The recovered catalyst can be reused for subsequent runs with only a gradual decrease in activity.
- He, Yan-Hong,Wang, Gang-Qiang,Guan, Zhi
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experimental part
p. 486 - 489
(2010/06/19)
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- CuCl-catalyzed cycloaddition of 1,3-butadiynes with primary amines: An atom-economic process for synthesis of 1,2,5-trisubsituted pyrroles
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1,3-Butadiynes underwent inter- and intramolecular double hydroamination with primary amines in the presence of CuCl at 100°C to afford 1,2,5-trisubsituted pyrroles in good to high yields.
- Zheng, Qingwei,Hua, Ruimao
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supporting information; experimental part
p. 4512 - 4514
(2010/10/02)
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- Access to 2,5-diamidopyrroles and 2,5-diamidofurans by Au(I)-catalyzed double hydroamination or hydration of 1,3-diynes
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(Figure presented) A Au(I)-catalyzed hydroamination or hydration of 1,3-diynes to access 2,5-diamidopyrroles and 2,5-diamidofurans has been developed. This method can also be expanded to 2,5-disubstituted furans and 1,2,5-trisubstituted pyrroles including the formation of deuterated heterocycles and 18O-labeled furans.
- Kramer, Soren,Madsen, Julie L. H.,Rottlaender, Mario,Skrydstrup, Troels
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supporting information; experimental part
p. 2758 - 2761
(2010/08/22)
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- Aggregation-induced emission enhancement of aryl-substituted pyrrole derivatives
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The relationship between the structures and light emission properties of five aryl-substituted pyrrole derivatives was studied during aggregation in THF-water mixtures. Only pentaphenylpyrrole clearly shows, however, an aggregation-induced emission enhanc
- Feng, Xiao,Tong, Bin,Shen, Jinbo,Shi, Jianbing,Han, Tianyu,Chen, Long,Zhi, Junge,Lu, Ping,Ma, Yuguang,Dong, Yuping
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scheme or table
p. 16731 - 16736
(2011/05/06)
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- Cobalt(ll) chloride as a novel and efficient catalyst for the synthesis of 1,2,5-trisubstituted pyrroles under solvent-free conditions
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CoCl2 is used as an efficient catalyst in the Paal-Knorr condensation of 2,5-hexadione with primary amines under solvent-free conditions, leading to the formation of pyrrole derivatives in excellent yield. This method is very easy, rapid, and high yielding reaction for the synthesis N-substituted pyrrole derivatives.
- De, Surya K.
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p. 592 - 595
(2008/12/22)
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- Sulfamic acid as a novel, efficient, cost-effective, and reusable solid acid catalyst for the synthesis of pyrroles under solvent-free conditions
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Paal-Knorr condensation of 2,5-hexadione with primary amines in the presence of a catalytic amount of sulfamic acid under solvent-free conditions has been accomplished with an excellent yield. This is a very easy, rapid, and high-yielding reaction for the synthesis N-substituted pyrrole derivatives. Copyright Taylor & Francis Group, LLC.
- De, Surya K.
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p. 803 - 809
(2008/09/16)
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- Simple synthesis of pyrroles under solvent-free conditions
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Paal-Knorr condensation of 2,5-hexadione with primary amines in the presence of a catalytic amount of praseodymium(III) trifluoromethanesulfonate under solvent-free conditions has been accomplished with an excellent yield. This method is a very easy, rapid, and high-yielding reaction for the synthesis of N-substituted pyrrole derivatives. Copyright Taylor & Francis Group, LLC.
- De, Surya K.
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experimental part
p. 2768 - 2774
(2009/04/11)
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- An approach to the Paal-Knorr pyrroles synthesis catalyzed by Sc(OTf)3 under solvent-free conditions
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A facile synthesis of N-substituted pyrroles by the Paal-Knorr condensation has been accomplished using a simple procedure. Among different metal triflates screened, 1 mol % Sc(OTf)3 efficiently promoted the reaction to give excellent yield (89-98%) under mild reaction conditions. Additionally, Sc(OTf)3 could be recovered easily after the reactions and reused without evident loss in activity.
- Chen, Jiuxi,Wu, Huayue,Zheng, Zhiguo,Jin, Can,Zhang, Xingxian,Su, Weike
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p. 5383 - 5387
(2007/10/03)
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- A straightforward highly efficient Paal-Knorr synthesis of pyrroles
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A straightforward simple synthesis of substituted pyrroles using bismuth nitrate-catalyzed modified Paal-Knorr method has been accomplished with an excellent yield. This method produces pyrroles with multicyclic aromatic amines.
- Banik, Bimal K.,Banik, Indrani,Renteria, Mercy,Dasgupta, Swapan K.
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p. 2643 - 2645
(2007/10/03)
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- Microwave mediated facile one-pot synthesis of polyarylpyrroles from but-2-ene- and but-2-yne-1,4-diones
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Several pyrrole derivates with multiple aryl substituents were prepared conveniently in a one pot-reaction from but-2-ene-1,4-diones and but-2-yne-1,4-diones via hydrogenation of the carbon-carbon double bond/triple bond followed by amination-cyclization. The reaction could be performed with ammonium formate or alkyl/arylammonium formates under Pd/C in polyethylene glycol-200 (PEG-200) under microwave irradiation. Using this procedure, different aryl-substituted pyrroles were prepared. Furthermore, studies on microwave vs thermal conditions indicate faster heating under microwave conditions was responsible for rate enhancement.
- Rao, H. Surya Prakash,Jothilingam,Scheeren, Hans W.
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p. 1625 - 1630
(2007/10/03)
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- One-pot synthesis of pyrrole derivatives from (E)-1,4-diaryl-2-butene-1,4-diones
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2,5-Di- and 1,2,5-trisubstituted pyrrole derivatives can be prepared conveniently from (E)-1,4-diaryl-2-butene-1,4-diones in a one-pot operation through domino-pathways via palladium-assisted transfer hydrogenation followed by a Paal-Knorr reaction using ammonium formate and its analogs.
- Surya Prakash Rao,Jothilingam
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p. 6595 - 6597
(2007/10/03)
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- Photochemistry of N-heterocycles. 7: Light induced reductive ring contractions of sixmembered cyclic iminium ions
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Photochemically induced reductive ring contractions, previously observed for 2,5-dihydro-1,2,4-triazines, have also been verified for 1,4-dihydropyrimidines 2a,b, the dihydro-1,2,4,5-tetrazine 9, and dihydro-1,3,5-triazines 11a,b giving rise to fivemembered fully unsaturated heterocycles (pyrroles 4a,b, imidazoles 13a,b, and triazole 10, respectively). The 1,4-dihydropyrazines 15a-j tend to decompose in acidified 2-propanol in the dark, but on irradiation they also undergo reductive ring contraction furnishing solely the 1,2,5-triarylpyrroles 16a-d rather than the (a priori also possible) isomeric 1,3,4-triarylpyrroles 17a-d. In contrast, the 3,6-diphenylpyrid-azine 18 gives the 4-isopropyl-analogue 19 in low yield upon irradiation in hydrogen chloride saturated 2-propanol. Wiley-VCH Verlag GmbH, 2000.
- Nagy, Jozsef,Madarasz, Zoltan,Rapp, Rudolf,Szoelloesy, Aron,Nyitrai, Jozsef,Doepp, Dietrich
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p. 281 - 290
(2007/10/03)
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- Conversion of pyrroles into bi-1,2,5-thiadiazoles: A new route to biheterocycles
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Trithiazyl trichloride 1 converts 1,2,5-triphenylpyrrole 5 into its 3,4-dichloro derivative together with the isothiazole imine 6 and the imine hydrolysis product, the ketone 3. The best yield of the isothiazole 6 is obtained in the presence of 4 A molecular sieves (Table 1). Conversion of the pyrrole 5 into the isothiazole 6 is exactly analogous to the reaction of 1 with 2,5-diphenyl-furan and -thiophene. Other N-aryl and the related 2,5-diphenylpyrroles 8 give similar results (Table 2). However, 1-methyl-2,5-diphenylpyrrole 11 reacts with 1 in an entirely different way to give 4,4′-diphenyl-3,3′-bi-1,2,5-thiadiazole 12, in which two thiadiazole rings have been fused onto the pyrrole and the CH3N unit has been excised as HCN. The same product 12 is formed, in similar yields, by reaction of 1 with 1,4-diphenylbuta-1, 3-diyne and 1,4-diphenylbut-1-en-3-yne. Other N-alkyl 2,5-diphenylpyrroles 16 react similarly (Table 3), giving the best yield (70%) of bi-thiadiazole 12 in the presence of 4 A molecular sieves (Table 4). 1-Methyl- and 1-ethyl-3,4-dibromo-2,5-diphenylpyrrole also give 12, together with 3-(benzoyldichloromethyl)-4-phenyl-1,2,5-thiadiazole 21 in high combined yield. The formation of bi-1,2,5-thiadiazole 12 from N-alkylpyrroles represents a new dissection of the pyrrole ring and a new and very short route to an aromatic biheterocyclic system. Mechanisms which rationalise the different pathways observed are proposed for all of these reactions.
- Duan, Xiao-Guang,Rees, Charles W.
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p. 3189 - 3196
(2007/10/03)
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- Synthesis of Substituted Pyrroles by Intramolecular Condensation of a Wittig Reagent with the Carbonyl Group of a Tertiary Amide
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1,2,5-Trisubstituted pyrroles are obtained in 50-100percent yields by addition of the conjugate bases of open-chain analogues of Reissert compounds to the vinyltriphenylphosphonium cation, with subsequent cyclization by an intramolecular Wittig reaction and base-catalyzed elimination of hydrogen cyanide.
- Cooney, John V.,McEwen, William E.
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p. 2570 - 2573
(2007/10/02)
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