An approach to the Paal–Knorr pyrroles synthesis catalyzed by Sc(OTf)3 under solvent-free conditions

Chen, Jiuxi; Wu, Huayue; Zheng, Zhiguo; Jin, Can; Zhang, Xingxian; Su, Weike

doi:10.1016/j.tetlet.2006.05.085

Cited by 177 publications

(68 citation statements)

References 56 publications

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“…Classical methods for their preparation include the Knorr, 4 Hantzsch, 5 and PaalKnorr condensation reactions. [6][7][8][9][10][11][12][13][14][15][16] Among these methods, the most commonly used and straightforward approach for the preparation of pyrroles is the direct condensation of -diketones and amines (Paal-Knorr reaction) in the presence of protonic acids such as AcOH, 6 p-TsOH. 7 Some improved procedures were reported to utilize Lewis acids such as Bi(NO 3 ) 3 .…”

Section: Introductionmentioning

confidence: 99%

Indium(III)-catalyzed synthesis of N-substituted pyrroles under solvent-free conditions

Chen¹,

Liu²,

Yang³

et al. 2008

J. Braz. Chem. Soc.

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Vários pirróis N-substituídos foram sintetizados pela reação de -dicetonas (R 1 C(O) CH 2 CH 2 C(O)R 2 : R 1 , R 2 = Me, Ph) com aminas (RNH 2 : R = Alkyl, Aryl, TsNH) ou diaminas (1,6-diaminohexano and 1,2-diaminoetano) na presença de tribrometo de índio, tricloreto de índio ou trifluorometanossulfonato de índio a temperatura ambiente e sem solventes. O protocolo envolve operações simples e os produtos são isolados em excelentes rendimentos (81-98%).A variety of N-substituted pyrroles have been synthesized by reacting -diketones (R 1 C(O) CH 2 CH 2 C(O)R 2 : R 1 , R 2 = Me, Ph) with amines (RNH 2 : R=Alkyl, Aryl, TsNH) or diamines (1,6-diaminohexane and 1,2-diaminoethane) in the presence of indium tribromide, indium trichloride or indium trifluoromethanesulfonate at room temperature under solvent-free conditions. The experiment protocol features simple operations, and the products are isolated in high to excellent yields (81-98%). Keywords: indium tribromide, indium trichloride, indium trifluoromethanesulfonate, pyrroles, solvent-free conditions IntroductionHeterocyclic small molecules play an important role in the search for new therapeutic and drug candidates. 1Pyrroles are an important class of heterocyclic compounds and are structural units found in a vast array of natural products, synthetic materials, and bioactive molecules, such as heme, vitamin B12, and cytochromes.2 Pyrroles also play crucial roles in nonlinear optical materials as well as in supramolecular chemistry.3 Therefore, the enormous number of procedures have been developed for the construction of pyrroles. Classical methods for their preparation include the Knorr, 4 Hantzsch, 5 and PaalKnorr condensation reactions. [6][7][8][9][10][11][12][13][14][15][16] Among these methods, the most commonly used and straightforward approach for the preparation of pyrroles is the direct condensation of -diketones and amines (Paal-Knorr reaction) in the presence of protonic acids such as AcOH, 6 p-TsOH. In continuation of our interest in Lewis acid-catalyzed and green chemistry organic reactions, 23 we herein wish to report a simple, practical and efficient method for the synthesis of pyrroles from -diketones and amines using indium(III) salt as catalyst at room temperature under solvent-free conditions (Scheme 1). Results and DiscussionInitially, the efficacy of various catalysts was tested in the model reaction under solvent-free condition at room temperature (Table 1). The results showed that InCl 3 , InBr 3 and In(OTf) 3 were superior to other Lewis acids with respect to reaction times and product yields. Entry 1 showed the blank reaction without addition of any catalyst, in this case only 29% 2,5-dimethyl-1-phenyl-1H-pyrrole (3a) was obtained after 24 h. For the sake of comparison, the reaction was carried out using other anhydrous chloride, such as ZnCl 2 , NiCl 2 , SrCl 2 and CuCl 2 under solvent free conditions (Entries 2-8). However, these chlorides showed lower activity than InCl 3 under same reaction conditions. We examined influence of solvents ...

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Section: Introductionmentioning

confidence: 99%

Indium(III)-catalyzed synthesis of N-substituted pyrroles under solvent-free conditions

Chen¹,

Liu²,

Yang³

et al. 2008

J. Braz. Chem. Soc.

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“…Current publications describe the use of solvent-free conditions with Lewis acid catalysts (24), microwave heating (25,26), ionic liquids (27), and ultrasound (28). Most of these processes lead to triand tetra-substituted pyrroles.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of highly substituted pyrroles using ultrasound in aqueous media

Almeida

2012

Green Chemistry Letters and Reviews

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A two-step protocol for the synthesis of highly substituted pyrroles in aqueous media and without catalyst is described. The first step is the dimerization of a 1,3-dicarbonyl compound by ceric ammonium nitrate/ultrasound to produce a tetracarbonyl derivative. This derivative is then combined with an amine in the absence of any catalysts to obtain the pyrrole via a PaalÁKnorr reaction. This route is an improvement when compared with classical methodologies toward Green Chemistry objectives.

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“…The heterogeneous catalyst could be recovered easily by applying an external magnet device and reused many times without significant loss of its catalytic activity. [41] I 2 0.5 h 92 [41] Bi(NO 3 ) 3 Á5H 2 O 1 0 h 9 5 [43] Microwave 0.5 min 90 [42] Sc(OTf) 3 30 min 94 [44] α-Zr(KPO 4 ) 2 2 h 78 [45] …”

Section: Discussionmentioning

confidence: 99%

Sulfamic acid heterogenized on functionalized magnetic Fe₃O₄ nanoparticles with diaminoglyoxime as a green, efficient and reusable catalyst for one‐pot synthesis of substituted pyrroles in aqueous phase

Veisi

Mohammadi

Gholami

2014

Applied Organom Chemis

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Surface functionalization of magnetic nanoparticles is an elegant way to bridge the gap between heterogeneous and homogeneous catalysis. We have conveniently loaded sulfonic acid groups on amino-functionalized Fe 3 O 4 nanoparticles affording sulfamic acid-functionalized magnetic Fe 3 O 4 nanoparticles (MNPs/DAG-SO 3 H) as an active and stable magnetically separable acidic nanocatalyst, which was characterized using X-ray diffraction, Fourier transform infrared and energy-dispersive X-ray spectroscopies, scanning and transmission electron microscopies, vibrating sample magnetometry and elemental analysis. The catalytic activity of MNPs/DAG-SO 3 H was probed through one-pot synthesis of N-substituted pyrroles from γ-diketones and primary amines in aqueous phase at room temperature. The heterogeneous catalyst could be recovered easily by applying an external magnet device and reused many times without significant loss of its catalytic activity.

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An approach to the Paal–Knorr pyrroles synthesis catalyzed by Sc(OTf)3 under solvent-free conditions

Cited by 177 publications

References 56 publications

Indium(III)-catalyzed synthesis of N-substituted pyrroles under solvent-free conditions

Indium(III)-catalyzed synthesis of N-substituted pyrroles under solvent-free conditions

Synthesis of highly substituted pyrroles using ultrasound in aqueous media

Sulfamic acid heterogenized on functionalized magnetic Fe₃O₄ nanoparticles with diaminoglyoxime as a green, efficient and reusable catalyst for one‐pot synthesis of substituted pyrroles in aqueous phase

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An approach to the Paal–Knorr pyrroles synthesis catalyzed by Sc(OTf)3 under solvent-free conditions

Cited by 177 publications

References 56 publications

Indium(III)-catalyzed synthesis of N-substituted pyrroles under solvent-free conditions

Indium(III)-catalyzed synthesis of N-substituted pyrroles under solvent-free conditions

Synthesis of highly substituted pyrroles using ultrasound in aqueous media

Sulfamic acid heterogenized on functionalized magnetic Fe3O4 nanoparticles with diaminoglyoxime as a green, efficient and reusable catalyst for one‐pot synthesis of substituted pyrroles in aqueous phase

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Product

Resources

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Sulfamic acid heterogenized on functionalized magnetic Fe₃O₄ nanoparticles with diaminoglyoxime as a green, efficient and reusable catalyst for one‐pot synthesis of substituted pyrroles in aqueous phase