- Hexafluoroisopropanol as solvent and promotor in the Paal-Knorr synthesis of N-substituted diaryl pyrroles
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An additive-free synthesis of challenging N-substituted aryl pyrroles from the often poorly soluble corresponding 1,4-diketones by means of the Paal-Knorr pyrrole synthesis is reported, which makes use of the unique properties of 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) as a solvent and reaction promotor. Our procedure offers simple execution and purification as well as easy scale-up and can be applied in the Paal-Knorr synthesis of a large number of structurally diverse pyrroles including the synthetically challenging tetra- and penta-substituted pyrroles in moderate to excellent yields. HFIP can also be used as solvent in the Paal-Knorr synthesis of furans and thiophenes; however, the solvent effect is more pronounced in synthesis of pyrroles.
- Schirmacher, Robert H.E.,R?sch, Daniel,Thomas, Franziska
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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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- Phosphine-Free Palladium-Catalyzed Direct Bisarylation of Pyrroles with Aryl Iodides on Water
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(Chemical Presented). The Pd-catalyzed bisarylation of pyrroles with aryl iodides on water is described. The reaction proceeds under mild reaction conditions, i.e., relatively low temperature (40 C) and phosphine-free.
- Cho, Beom Shin,Bae, Hyun Jung,Chung, Young Keun
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p. 5302 - 5307
(2015/05/27)
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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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- 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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- Electrocyclization reactions of 1-Aza- and 1-oxapentadienyl and -heptatrienyl cations: Synthesis of pyrrole and furan derivatives
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Quantum chemical DFT calculations (B3LYP/6-31+G) have been used to gain insight into the conformational and energy properties of the 1-aza- and 1-oxapentadienyl and -heptatrienyl cations 1, 2, 3, and 4. The calculated thermodynamic and kinetic data of the ring-closure reactions giving the cyclic products 5-14 are reported and discussed with respect to the experimental results. Experimentally, synthetic routes to the α,β-unsaturated carbonyl compounds 24 and 27, each with a leaving group in the γ-position, have been developed. These compounds have been investigated with respect to their ability to undergo 1,5-electrocyclization reactions to yield 2,5-disubstituted furans 28 upon heating in the presence of acid, presumably through the intermediate formation of the 1-oxapentadienyl cations 2. From the corresponding imine 29a the pyrrole 30d was obtained after treatment with tetrakis (triphenylphosphane) palladium. In the presence of benzylamine and the Pd° catalyst, the corresponding pyrroles 30a-c were formed from 24 and 27. The homologous α,β,γ,δ-unsaturated carbonyl compounds 31 afforded 2-vinyl-substituted furans 32 upon heating with acid, and the 2-vinyl-substituted pyrroles 34 on treatment with benzylamine and the Pd catalyst. No seven-membered heterocyclic rings were formed. Surprisingly, the α,β-unsaturated carbonyl compounds with two phenyl substituents at the γ-position also provided pyrrole derivatives 40 through a formal dimerization. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
- Alickmann, Dirk,Froehlich, Roland,Maulitz, Andreas H.,Wuerthwein, Ernst-Ulrich
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p. 1523 - 1537
(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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- 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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- Oxidative Halogenation of Substituted Pyrroles with Cu(II). Part I. Bromination of some 3-Acetylpyrroles
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3-Acetylpyrroles are brominated with copper(II) bromide.The reaction afforded almost quantitatively only nuclear monobromination.Evidence for the structures of final compounds was by mass spectrometry, 1H-nuclear magnetic resonance, ir, and elemental analysis.
- Petruso, S.,Caronna, S.,Sprio, V.
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p. 1209 - 1211
(2007/10/02)
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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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