- A SIMPLE AND EFFICIENT ROUTE TO β-SUBSTITUTED PYRROLES
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N-Phenylsulfonylpyrrole undergoes Friedel-Crafts acylation exclusively at the β-position of the pyrrole ring, thus allowing a simple and efficient synthesis of β-acylated pyrroles.
- Rokach, Joshua,Hamel, Pierre,Kakushima, Masatoshi,Smith, Graham M.
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- Friedel-Crafts acylation of pyrrole over ultrasonic-assisted phosphoric acid-modified Hβ zeolite
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Friedel-Crafts acylation of pyrrole with acetic anhydride was studied over different zeolites and an ultrasonic-assisted phosphoric acid-modified Hβ (P-Hβ-US) zeolite was found to have the best catalytic performance among all the zeolites examined. The conversion of acetic anhydride reached 98.8% and the selectivity to acetylpyrroles was 97.0% under the optimized conditions. The high activity of the P-Hβ-US zeolite is attributed to the increase of weak acid sites, caused by the synergistic effect between the phosphoric acid modification and ultrasound. Moreover, the carbonaceous deposits, mainly due to the adsorption of reactants and products, on the surface acid sites and the blockage of the pores is believed to be the reason for the deactivation of the reused P-Hβ-US zeolite, confirmed from the Brunauer-Emmett-Teller (BET) method, scanning electron microscopy, and X-ray photoelectron spectroscopy. Furthermore, the catalyst activity can be recovered effectively by a subsequent calcination. Springer Science+Business Media B.V. 2011.
- Bai, Guo Yi,Yang, Yong Hui,Ma, Zheng,Xu, Jian Zhong,Qiu, Man De,He, Fei,Yan, Xi Long,Dou, Hai Yang
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- Synthesis of industrially important aromatic and heterocyclic ketones using hierarchical ZSM-5 and Beta zeolites
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Hierarchical ZSM-5 and Beta zeolites were investigated in the synthesis of wide range of industrially important aromatic/heterocyclic ketones by Friedel-Crafts acylation and benzoylation reactions. For comparative study, conventional ZSM-5 and Beta, and amorphous mesoporous Al-MCM-41 were investigated. Hierarchical zeolites were prepared by multi-ammonium structure directing agents whereas conventional zeolites were prepared by mono-ammonium structure directing agents. Among the catalysts investigated in this study, hierarchical Beta exhibited the highest reactant conversion in the acylation and benzoylation reactions. In this study, the systematic assessment of the catalytic activity of acid catalysts for wide range of aromatic and heterocyclic compounds is shown under one umbrella. To the best of our knowledge, these reactions over hierarchical zeolites (ZSM-5 and Beta) are reported here for the first time. Structure activity relationship is explained based on the physico-chemical properties, molecular size, reactivity of reactants, and reaction mechanism. Catalysts can be easily recovered and reused with negligible loss in the catalytic activity.
- Kore, Rajkumar,Srivastava, Rajendra,Satpati, Biswarup
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- Pyrrole Hemithioindigo Antimitotics with Near-Quantitative Bidirectional Photoswitching that Photocontrol Cellular Microtubule Dynamics with Single-Cell Precision**
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We report the first cellular application of the emerging near-quantitative photoswitch pyrrole hemithioindigo, by rationally designing photopharmaceutical PHTub inhibitors of the cytoskeletal protein tubulin. PHTubs allow simultaneous visible-light imaging and photoswitching in live cells, delivering cell-precise photomodulation of microtubule dynamics, and photocontrol over cell cycle progression and cell death. This is the first acute use of a hemithioindigo photopharmaceutical for high-spatiotemporal-resolution biological control in live cells. It additionally demonstrates the utility of near-quantitative photoswitches, by enabling a dark-active design to overcome residual background activity during cellular photopatterning. This work opens up new horizons for high-precision microtubule research using PHTubs and shows the cellular applicability of pyrrole hemithioindigo as a valuable scaffold for photocontrol of a range of other biological targets.
- Akhmanova, Anna,Heise, Constanze,Meiring, Joyce C. M.,Pettersson, Linda N.,Sailer, Alexander,Thorn-Seshold, Julia,Thorn-Seshold, Oliver
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supporting information
p. 23695 - 23704
(2021/10/05)
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- Reactions of nitrilium salts with indole and pyrrole and their derivatives in the synthesis of imines, ketones and secondary amines
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Abstract Reactions of N-methyl- and N-ethyl-nitrilium salts with indole and pyrrole and their derivatives yield imines or imine salts in good yields. The related imines are obtained from the salts after careful basification and hydrolysis of the imine salts or the imines by heating with aqueous base give the related ketones in good yields. Alternatively, the imine salts can be reduced using sodium borohydride in methanol to give the related secondary amines.
- Giles, Robert G.,Heaney, Harry,Plater, M. John
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p. 7367 - 7385
(2015/08/24)
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- Synthesis of 2,2′-bipyrrole-5-carboxaldehydes and their application in the synthesis of B-ring functionalized prodiginines and tambjamines
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Facile, versatile, and cost-effective synthetic routes for the preparation of a range of new 3-alkyl-, 4-alkyl-, 3,4-dialkyl-, and 3-halo-4-alkyl-2, 2′-bipyrrole-5-carboxaldehydes have been developed. These 2,2′-bipyrrole-5-carboxaldehydes offer interesting potential as building blocks for making bioactive natural and unnatural products, as demonstrated by the synthesis of B-ring functionalized prodiginines (PGs) and tambjamines.
- Kancharla, Papireddy,Reynolds, Kevin A.
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p. 8375 - 8385
(2013/09/02)
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- Direct synthesis of chiral 1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazines via a catalytic asymmetric intramolecular aza-Friedel-Crafts reaction
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The direct asymmetric intramolecular aza-Friedel-Crafts reaction of N-aminoethylpyrroles with aldehydes catalyzed by a chiral phosphoric acid represents the first efficient method for the preparation of medicinally interesting chiral 1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazines with high yields and high enantioselectivities. This strategy has been shown to be quite general toward various aldehydes and pyrrole derivatives.
- He, Yuwei,Lin, Maohui,Li, Zhongmin,Liang, Xinting,Li, Guilong,Antilla, Jon C.
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supporting information; scheme or table
p. 4490 - 4493
(2011/10/09)
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- Amberlyst-15 catalyzed acetylation of heteroaromatics with acetic anhydride under solvent free conditions
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Amberlyst-15 has been found to be an efficient reusable heterogeneous catalyst for acetylation of indole, 2-methylindole and pyrrole with acetic anhydride under solvent free conditions.
- Das, Biswanath,Pal, Rammohan,Banerjee, Joydeep,Mahender,Holla, Harish,Venkateswarlu
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p. 198 - 200
(2007/10/03)
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- Aluminum dodecatungstophosphate (AlPW12O40) as a non-hygroscopic Lewis acid catalyst for the efficient Friedel-Crafts acylation of aromatic compounds under solvent-less conditions
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Stable and non-hygroscopic aluminum dodecatungstophosphate (AlPW 12O40), which is prepared easily from cheap and commercially available compounds was found to be an effective catalyst for Friedel-Crafts acylation reactions using carboxylic acids, acetic anhydride and benzoyl chloride in the absence of solvent under mild reaction conditions.
- Firouzabadi, Habib,Iranpoor, Nasser,Nowrouzi, Farhad
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p. 10843 - 10850
(2007/10/03)
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- Aromatic heterocycle compounds having HIV integrase inhibiting activities
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A compound of the formula (I): wherein X is hydroxy, protected hydroxy or optionally substituted amino; Y is —COORAwherein RAis hydrogen or ester residue, —CONRBRCwherein RBand RCeach is independently hydrogen or amide residue, optionally substituted aryl or optionally substituted heteroaryl; and A1is optionally substituted heteroaryl; provided that a compound wherein Y and/or A1is optionally substituted indol-3-yl is excluded, a tautomer, a prodrug, a pharmaceutically acceptable salt or a hydrate thereof has an inhibitory activity against an integrase.
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- Diethoxymethyl protected pyrroles: Synthesis and regioselective transformations
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Treatment of the acceptor-substituted pyrroles 1a-k with neat triethyl orthoformate gives access to the diethoxymethyl (DEM) protected derivatives 2a-k in high yield. Convenient and mild cleavage was achieved by subsequent treatment of the DEM-pyrroles 2a-k with trifluoroacetic acid in acetonitrile and aqueous NaOH at room temperature. DEM protection proved suitable for a variety of regioselective transformations involving directed orthometalation and iodine-magnesium exchange processes. Furthermore, electrophilic halogenations and Pd-catalyzed coupling reactions were also carried out.
- Bergauer,Gmeiner
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p. 2281 - 2288
(2007/10/03)
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- β-Acylation of ethyl pyrrole-2-carboxylate by Friedel-Crafts acylation: Scope and limitations (synthetic studies on indoles and related compounds. XXXVIII
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The Friedel-Crafts acylation of ethyl pyrrole-2-carboxylate (3) was studied under several conditions using various Lewis acids and acyl chlorides. The acylation with various acyl chlorides in the presence of aluminum chloride gave exclusively ethyl 4-acylpyrrole-2-carboxylate (5), whereas weaker Lewis acids such as zinc chloride and boron trifluoride etherate gave a mixture of ethyl 4- and 5-acylpyrrole-2-carboxylates.
- Tani,Ariyasu,Nishiyama,Hagiwara,Watanabe,Yokoyama,Murakami
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- General Methods for Synthesizing 2,4-Diacylpyrroles and their Precursors Containing One or Two Masked Acyl Groups
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A thorough study of the synthesis of 2,4-diacylpyrroles by direct acylation of pyrrole and 2- and 3-acylpyrroles is reported.Among these, Friedel-Crafts acylation of 3-acylpyrroles is the most general and advantageous method because it utilises easily accessible starting materials.In addition it is always regiospecific and readily provides 2,4-diacylpyrroles containing identical or different acyl groups in very high yields (81-100percent) under mild conditions, Alternative procedures concern the synthesis of precursors of 2,4-diacylpyrroles containing one or two acyl groups masked by a 1,3-benzodithiolyl or 1,3-benzoxathiolyl group and subsequent hydrolysis with HgO-35percent aq.HBF4-Me2SO.Overall yields are always good (52-60percent).Indirect acylation constitutes a secure complement to direct acylation when it is necessary to operate in the presence of protected acyl groups.
- Cadamuro, Silvano,Degani, Iacopo,Dughera, Stefano,Fochi, Rita,Gatti, Antonella,Piscopo, Laura
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p. 273 - 284
(2007/10/02)
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- Gas-phase heteroaromatic substitution. 11. Electron transfer mechanism in the gas-phase acylation of simple five-membered heteroarenes
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The results of a study of the gas-phase reactions of unsaturated carbocations, such as the CH3CO+ ion from γ-radiolysis of CH3F/CO mixtures, and the C6H4TCO+ ion from the β-decay of 1,4-ditritiobenzene in the presence of CO, with pyrrole, N-methylpyrrole, furan, and thiophene, are reported.In all systems investigated, acylated heteroarenes represent the predominant reaction products, accompanied by the methylated derivatives in the CH3F/CO radiolytic mixtures, and by the phenylated ones in the 1,4-ditritiobenzene/CO decay samples.All substrates investigated are found to undergo predominat α substitution by both acetyl (88.6-98.4percent (pyrrole); 90.8-98.7percent (N-methylpyrrole); 97.2-98.9percent (furan); 94.9-98.6percent (thiophene)) and benzoyl cations (92.6-96.5percent (pyrrole)) under all conditions.The predominant formation of the α-acylated pyrroles from both reactants (>88percent), whose relative yields appear unaffected within the temperature interval from 303 to 383 K, indicates, in agreement with ancillary FT-ICR mass spectrometric evidence, that gas-phase acylation reactions toward simple five-membered heteroarenes proceed via a two-step substitution mechanism, involving a quasi-resonant single-electron transfer (SET) step followed by recombination of the ensuing radical - radical ion pair.By virtue of this entropy-favored mechanism, gaseous electrophiles with relatively high SCF STO-3G calculated LUMO energies such CH3CO+ and C6H4TCO+ are effectively oriented toward the "soft" Cα sites of the selected heteroarenes, at variance with Klopman's Charge and Frontier Orbital Control predictions.The behavior of gaseous acylating reactants toward simple heteroarenes is discussed and compared with that of other gaseous electrophiles, whose reactivity appears instead in qualitative agreement with Klopman's model.
- Filippi, Antonello,Occhiucci, Giorgio,Sparapani, Cinzia
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p. 740 - 748
(2007/10/02)
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- N-(Triisopropylsilyl)pyrrole. A Progenitor "Par Excellence" of 3-Substituted Pyrroles
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A very effective strategy has been devised for the synthesis of 3-substituted pyrroles based on the use of the triisopropylsilyl (TIPS) moiety as a sterically demanding nitrogen substituent to obstruct the attack of electrophilic reagents at the α positions. 1-(Triisopropylsilyl)pyrrole (1) undergoes highly preferential kinetic electrophilic substitution at the β position with a variety of electrophiles (Br+, I+, NO2+, RCO+, etc.) and fluoride ion induced desilylation of the products provides the corresponding 3-substituted pyrroles in good overall yields.Competitive trifluoroacetylation experiments demonstrate that substitution of TIPS-pyrrole at the α positions is decelerated by a factor of >104, vs pyrrole at the same sites, without affecting reactivity at the β positions. 1-(Triisopropylsilyl)-3-bromopyrrole (2) is readily converted into the 3-lithio compound 44 by bromine-lithium interchange with alkyllithium reagents.This previously unavailable, formal equivalent of 3-lithiopyrrole is itself an excellent source of a wide range of β-substituted pyrroles, many of which would not be directly preparable from 1.TIPS-pyrrole can be 3,4-dihalogenated and these compounds undergo sequential halogen-metal interchange trapping reactions.This process is exemplified by an efficient, three-step synthesis of the antibiotic verrucarin E (63) from the dibromo compound (5).
- Bray, Brian L.,Mathies, Peter H.,Naef, Reto,Solas, Dennis R.,Tidwell, Thomas T.,et al.
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p. 6317 - 6328
(2007/10/02)
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- First Reactions of Dialkoxycarbenium Tetrafluoroborates with Pyrroles, 5H-Dibenzazepines, and Electron-Rich Arenes
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Pyrrole (2a) and 2,5-dimethylpyrrole (2b) react with the dialkoxycarbenium tetrafluoroborates 1a-1c under kinetic control to yield the corresponding acylpyrrole derivatives. 5H-Dibenzazepine (9a) and the 10,11-dihydro derivative 9b react only with the most elecrophilic of the series of electrophiles tested, namely, diethoxycarbenium tetrafluoroborate (1a), to furnish the corresponding formyl derivatives.Similarly, in arene chemistry, the highly electron-rich N,N-dimethylaniline (13a) and 1,3,5-trimethoxybenzene (13b) are formylated by reaction with 1a.
- Pindur, U.,Flo, C.
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p. 1563 - 1568
(2007/10/02)
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- Synthesis of 2-Alkylputrescines from 3-Alkylpyrroles
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Acylation of 2-(trichloroacetyl)pyrrole gave the 4-acyl derivatives (from 4-formyl to 4-hexanoyl) in good yields.Alkaline treatment gave corresponding 4-acyl-2-pyrrolecarboxylic acids, were decarboxylated to the 3-acylpyrroles by prior conversion to the 3-acyl-2,4,5-triiodopyrroles followed by hydrogenolysis.The 3-acylpyrroles were reduced by treatment with hydrazine in alkaline medium to the 3-alkylpyrroles.The latter were ring-opened by treatment with hydroxylamine in the presence of bicarbonate to give the dioximes of the corresponding 2-alkylsuccinaldehydes, which were then reduced to the 2-alkylpurescines (1,4-diaminobutanes).Ring-opening of 2,3-dimethylpyrrole followed by reduction of the dioxime gave 1,2-dimethylputrescine; the same sequence gave 1,3-dimethylputrescine from 2,4-dimethylpyrrole, while 3,4-dimethylpyrrole did not ring-open and gave the dioxime of 3,4-dimethylmaleimide.
- Garrido, Daniel O. A.,Buldain, Graciela,Ojea, Maria I.,Frydman, Benjamin
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p. 403 - 407
(2007/10/02)
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- PYRROLE CHEMISTRY. PART XXIX. A RE-EXAMINATION OF THE DECARBOXYLATION OF 4-ACETYL-, 4-FORMYL- AND 4-CYANO-PYRROLE-2-CARBOXYLIC ACIDS
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Decarboxylation of the readily available 4-acyl-2-pyrrolecarboxylic acids has been neglected owing to the poor yields reported in the literature.This study shows that high yields are possible under the correct reaction conditions.
- Anderson, Hugh J.,Clase, J. Andrew,Loader, Charles E.
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p. 401 - 408
(2007/10/02)
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- FRIEDEL-CRAFTS ACYLATION OF 1-TERT-BUTYLDIMETHYLSILYLPYRROLE, A VERY SHORT AND SIMPLE ROUTE TO 3-SUBSTITUTED PYRROLES.
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1-tert-Butyldimethylsilylpyrrole undergoes Friedel-Crafts acylation almost exclusively at β-position giving after sodium fluoride supported hydrolysis the 3-pyrroloketones.
- Simchen, Gerhard,Majchrzak, Michal W.
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p. 5035 - 5036
(2007/10/02)
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- 3-Lithiopyrroles by Halogen-Metal Interchange of 3-Bromo-1-(triisopropylsilyl)pyrroles. Synthesis of Verrucarin E and Other 3-Substituted Pyrroles.
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3-Lithio-1-(trimethylsilyl)pyrrole (7, Scheme 2), obtained by halogen-metal interchange from the 3-bromo compound 2, reacted with various electrophilic reagents to provide products, which on fluoride ion desilylation, gave 3-substituted pyrroles in good overall yields.One such pyrrole 13 (Scheme 3), was converted into 2-formyl-3-octadecylpyrrole (14), reputed to be a metabolite of the marine sponge Oscarella lobularis. 3,4-Dibromo-1-(triisopropylsilyl)pyrrole (5) was efficiently transformed, by a process involving two conscutive bromine-lithium exchange reactions (Scheme 4), into the antibiotic verrucarin E 17.
- Muchowski, Joseph M.,Naef, Reto
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p. 1168 - 1172
(2007/10/02)
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- Regioselective Synthesis of Acylpyrroles
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The regioselective synthesis of several pyrrole derivatives is described.AlCl3-catalyzed acylation reactions of 1-(phenylsulfonyl)pyrrole (1) give 3-acyl derivatives, whereas the corresponding BF3*OEt2-catalyzed reactions give 2-acyl derivatives predominantly.Mild alkaline hydrolysis gives the corresponding acyl-1H-pyrroles in excellent yields.AlCl3-catalyzed reactions of 1 with 1,1-dichloromethyl methyl ether and oxalyl chloride give 1-(phenylsulfonyl)-2-formylpyrrole (6) and 1-(phenylsulfonyl)-2-(chlorocarbonyl)pyrrole (7), respectively. 3-Pyrrolylacetic acid (10) was prepared by thallium(III) nitrate promoted rearrangement of 1-(phenylsulfonyl)-3-acetylpyrrole (2a).Trifluoroacetic anhydride catalyzed cyclization of 4-butyric acid (14) gives 1-(phenylsulfonyl)-7-oxo-4,5,6,7-tetrahydroindole (17).Attempts to cyclize 14 at the 4-position have been unsuccessful.
- Kakushima, Masatoshi,Hamel, Pierre,Frenette, Richard,Rokach, Joshua
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p. 3214 - 3219
(2007/10/02)
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- PYRROLE CHEMISTRY XXV: A SIMPLIFIED SYNTHESIS OF SOME 3-SUBSTITUTED PYRROLES
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A new synthesis is reported which allows the rapid preparation in good yield of 3-aroyl-, 3-acetyl- and 3-nitro- pyrroles from pyrrole utilizing the 1-benzenesulfonyl group as a blocking group.
- Xu, Ru Xun,Anderson, Hugh J.,Gogan, Niall J.,Loader, Charles E.,McDonald, Robert
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p. 4899 - 4900
(2007/10/02)
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- Acid-Mediated Rearrangement of Acylpyrroles
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N-Alkyl-2-acylpyrroles are converted by strong anhydrous acid to 1-alkyl-3-acylpyrroles.An equilibrium mixture of 2- and 3-acylpyrrole is produced by treatment of a 2- or 3-acyl NH pyrrole with acid.Pyrrolecarboxaldehydes similarly afford isomeric mixtures.A cross-ring migration, 7->8, is observed when the adjacent position is blocked.The mechanism of acid-mediated rearrangement of acylpyrroles is discussed.
- Carson, John R.,Davis, Nancy M.
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p. 839 - 843
(2007/10/02)
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- Pyrrole chemistry. XXII. A "one-pot" synthesis of some 4-acylpyrrole-2-carboxaldehydes from pyrrole
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The Vilsmeier-Haack intermediates formed from pyrrole and from 1-methylpyrrole may be acylated under normal Friedel-Crafts conditions.Hydrolytic work-up then gives 4-acylpyrrole-2-carboxaldehydes in good yield.The methoxide/methanol treatment of the 4-trichloroacetylated intermediate leads to methyl 2-formylpyrrole-4-carboxylate.These are all "one-pot" syntheses from pyrrole.The formyl group has been removed from several of the products thus affording some 3-acylpyrroles in two operations.
- Anderson, Hugh J.,Loader, Charles E.,Foster, Aidan
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p. 2527 - 2530
(2007/10/02)
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