- Aroylation of Electron-Rich Pyrroles under Minisci Reaction Conditions
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The development of Minisci acylation on electron-rich pyrroles under silver-free neutral conditions has been reported featuring the regioselective monoacylation of (NH)-free pyrroles. Unlike conventional Minisci conditions, the avoidance of any acid that could result in the polymerization of pyrroles was the key to success. The umpolung reactivity of the nucleophilic acyl radical, generated in situ from arylglyoxylic acid, could help explain the mechanism of product formation with electron-rich pyrroles. Alternatively, the nucleophilic substitution of the acyl radical on the electron-deficient pyrrole radical cation is proposed.
- Laha, Joydev K.,Kaur Hunjan, Mandeep,Hegde, Shalakha,Gupta, Anjali
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p. 1442 - 1447
(2020/02/22)
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- Selective Methylation of Amides, N-Heterocycles, Thiols, and Alcohols with Tetramethylammonium Fluoride
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We herein disclose the use of tetramethylammonium fluoride (TMAF) as a direct and selective methylating agent of a variety of amides, indoles, pyrroles, imidazoles, alcohols, and thiols. The method is characterized by operational simplicity, wide scope, and ease of purification. Our computational studies suggest a concerted methylation-deprotonation as the preferred reaction pathway.
- Cheng, Hong-Gang,Pu, Maoping,Kundu, Gourab,Schoenebeck, Franziska
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supporting information
p. 331 - 334
(2019/12/30)
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- A Novel and Chemoselective Process of N -Alkylation of Aromatic Nitrogen Compounds Using Quaternary Ammonium Salts as Starting Material
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The process of N-alkylation of several pyrroles, indoles, and derivative heterocycles is herein described, using quaternary ammonium salts as the source of an alkylating agent. These reactions were carried out on several heterocyclic rings with triethylbenzylammonium chloride or tetradecyltrimethylammonium bromide and an NaOH solution at 50%, leading to a chemoselective N-alkylated product and an average yield of 73%. This is an alternative process to the traditional benzylation and methylation of N-heterocycles with direct handling of alkyl halides.
- González-González, Carlos A.,Vega, Juan Javier Mejía,Monroy, Ricardo García,González-Calderón, Davir,Corona-Becerril, David,Fuentes-Benítes, Aydeé,Mascarúa, Joaquín Tamariz,González-Romero, Carlos
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- Synthesis of hetaryl-substituted 1,2,4-trithiolanes via a three-component reaction with dihetaryl thioketones, benzyl azide, and 2,2,4,4-tetramethyl-3-thioxocyclobutanone
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The three-component reactions with a hetaryl thioketone, 2,2,4,4-tetramethyl-3-thioxocyclobutanone, and excess benzyl azide performed at 60°C in the presence of LiClO4 lead to the formation of two types of 1,2,4-trithiolanes. As the major produ
- Mlosto, Grzegorz,Celeda, Malgorzata,Linden, Anthony,Heimgartner, Heinz
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- Acylation of pyrroles and their free (N-H)-derivatives via palladium-catalyzed carbopalladation of nitriles
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An efficient regioselective synthesis of 2-acylpyrroles via palladium-catalyzed addition of pyrroles with benzonitriles and subsequent hydrolysis is developed. The direct acylation reaction of protected as well as (NH)-free pyrroles proceeded smoothly to
- Jafarpour, Farnaz,Hazrati, Hamideh,Darvishmolla, Masoumeh
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supporting information
p. 3784 - 3788
(2015/02/19)
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- Solvent free synthesis of 2-acylpyrroles and its derivatives catalysed by reuseable zinc oxide
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A highly efficient procedure for preparing 2-acylpyrroles and its derivatives is described. The products were obtained through regioselective Friedel-Crafts reactions of pyrroles and its derivatives with alkyl or aryl acid chlorides catalysed by zinc oxide under solvent-free conditions. This method has the advantages of green chemistry, operational simplicity, solvent-free conditions, and recoverable catalyst.
- Zhang, Shuguang,Feng, Chengliang,Cai, Jin,Chen, Junqing,Hu, Huayou,Ji, Min
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p. 480 - 482
(2013/09/12)
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- Iodide as an activating agent for acid chlorides in acylation reactions
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Acid chlorides can be activated using a simple iodide source to undergo nucleophilic attack from a variety of relatively weak nucleophiles. These include Friedel-Crafts acylation of N-methylpyrroles, N-acylation of sulfonamides, and acylation reactions of hindered phenol derivatives. The reaction is believed to proceed through a transient acid iodide intermediate.
- Wakeham, Russell J.,Taylor, James E.,Bull, Steven D.,Morris, James A.,Williams, Jonathan M. J.
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supporting information
p. 702 - 705
(2013/04/11)
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- Friedel - Crafts acylation of pyrroles and indoles using 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) as a nucleophilic catalyst
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1,5-Diazabicyclo[4.3.0]non-5-ene (DBN) has been shown to be an effective catalyst for the regioselective Friedel - Crafts C-acylation of pyrroles and indoles in high yields. A detailed mechanistic study implies that DBN is acting as a nucleophilic organocatalyst, with the X-ray crystal structure of a key N-acyl-amidine intermediate having been determined for the first time.
- Taylor, James E.,Jones, Matthew D.,Williams, Jonathan M. J.,Bull, Steven D.
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supporting information; experimental part
p. 5740 - 5743
(2011/03/18)
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- Unexpectedly high activity of Zn(OTf)2·6H2O in catalytic Friedel-Crafts acylation reaction
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Zn(OTf)2·6H2O was used to promote Friedel-Crafts acylation of aromatics. The work describes the high activity and efficiency of Zn(OTf)2·6H2O in acylation of aromatics, and the catalyst has surpassed most metal triflates in dispensing when dried at high temperature under vacuum before use. Copyright Taylor & Francis Group, LLC.
- He, Fei,Wu, Huayue,Chen, Jiuxi,Su, Weike
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p. 255 - 264
(2008/03/17)
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- Vilsmeier-Haack preparation of 2-acylpyrroles using bis(trichloromethyl) carbonate and N,N-dimethylacylamines
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A series of 2-acylpyrroles were synthesized by using bis(trichloromethyl) carbonate and N,N-dimethylacylamines as Vilsmeier-Haack reagents under mild conditions in good yields.
- Shi,Su,Shan
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p. 1019 - 1021
(2007/10/03)
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- Ytterbium (III) trifluoromethanesulfonate catalysed Friedel-Crafts acylation of 1-methylpyrrole in ionic liquid
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In the presence of a catalytic amount of ytterbium (III) trifluoromethanesulfonate [Yb(OTf)3], 1-methylpyrrole can easily react with acyl chlorides in an ionic liquid [bpy][BF4](bpy=1- butylpyridine) to form corresponding ketones in satisfactory yield. The recyclability of the ionic liquid/catalyst system is demonstrated.
- Su, Weike,Wu, Chunlei,Su, Hao
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- Oxidative radical cyclization to pyrroles under reducing conditions. Reductive desulfonylation of α-sulfonylpyrroles with tri-n-butyltin hydride
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1-(2-Bromobenzyl)-2-alkanesulfonylpyrroles (1c, 1d) and 1-(4-bromobutyl)-2-methylsulfonylpyrrols (8) undergo oxidative radical cyclization with partial or complete reductive desulfonylation to the pyrrolizidine derivatives 5 and 9 by an AIBN initiated reaction with tri-n-butyltin hydride.These cyclizations are suggested to proceed via a pseudo SRN1 process involving radical addition to the α position of the pyrrole nucleus not bearing the sulfonyl group.Reductive removal of the alkylsulfonyl moiety is proposed to occur in a second process after completion of the oxidative radical cyclization.The site of the radical addition is supported by deuterium labelling studies.Consistent with the timing of the loss of the sulfonyl group is that 2-alkylsulfonylpyrroles 11 are reductively desulfonylated under the same conditions that effect the oxidative radical cyclizations.
- Antonio, Yulia,Cruz, Ma. Elizabeth De La,Galeazzi, Edvige,Guzman, Angel,Bray, Brian L.,et al.
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- Differential Reactivity of β-Amino Enones and 3-Dimethylaminoacrylaldehyde towards α-Amino Derivatives
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Unsubstituted β-amino enones react with α-amino derivatives by a well established route with implies a fast transamination process - 1,4-addition followed by elimination - and cyclodehydration of the intermediate to 3-functionalized pyrroles.In contrast, 3-dimethylaminoacrylaldehyde undergoes 1,2-addition followed by cyclization to give the final 2-substituted pyrroles.Isolation of the intermediates supports the proposed mechanism for each reaction.
- Alberola, Angel,Andres, Jose M.,Gonzalez, Alfonso,Pedrosa, Rafael,Vicente, Martina
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p. 2681 - 2685
(2007/10/02)
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- Acylation of Pyrrole and N-Methylpyrrole with 1,3-Benzoxathiolium Tetrafluroborates. A High-Yield Method for the Synthesis of Diacylpyrroles
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2-Substituted 1,3-benzoxathiolium tetrafluoroborates (I) were used as masked acylating agents for pyrrole and N-methylpyrrole.The reactions on pyrrole (II) were regiospecific, and according to the molar ratio of the reagents (I:II = 1:3 or 2.5-3:1), 2-acylpyrroles were obtained in moderate to good yields (38-82percent) and 2,5-diacylpyrroles were obtained in excellent yields (in most cases, quantitative).The reactions on N-methylpyrrole (III) were not regioselective, and both α- and β-positions were attacked.So, depending on the molar ratio of the reagents (I:III = 1:3 or 2,5-3:1), 2- and 3-acyl-N-methylpyrroles (9-51percent and 27-68percent yields, respectively) and 2,4- and 2,5-diacyl-N-methylpyrroles (60-93percent and 17-40percent, respectively) were obtained.A very interesting feature of the new method is the possibility of introducing two identical or different acyl groups in the pyrrole ring under mild conditions. 1H and 13C NMR spectra of all the new compounds and IR spectra, recorded in the gas phase, of 2- and 3-acylpyrroles and of 2,4- and 2,5-diacylpyrroles are reported.
- Barbero, Margherita,Cadamuro, Silvano,Degani, Iacopo,Fochi, Rita,Gatti, Antonella,Regondi, Valeria
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p. 2245 - 2250
(2007/10/02)
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- Rate Measurements of Certain Vilsmeier-Haack Reactions. Part 3. The Reactivities of Various Pyrrole Substrates
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The rates of reaction of six pyrrole substrates with the Vilsmeier-Haack reagent derived from NN-dimethylbenzamide (and in some cases from N-benzoylmorpholine or NN-diethylbenzamide) and phosphoryl chloride were measured.The deactivating effect on substit
- White, Julian,McGillivray, George
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p. 1179 - 1182
(2007/10/02)
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- Preparation of β-acyl pyrroles
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A process for rearranging α-acyl pyrroles to β-acyl pyrroles which comprises reacting the former with an excess of a strong, anhydrous, non-oxidizing acid, preferably with heating.
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