Synthese von Furfuranderivaten aus dem Diacetbernsteinsäureester

Knorr, Ludwig

doi:10.1002/cber.188401702254

Cited by 233 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. 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).…”

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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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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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“…6,7 Equivalent amounts of starting materials were used in the reaction, and the compounds were synthesized under nitrogen. Ethanol was used as solvent.…”

Section: Methodsmentioning

confidence: 99%

“…3,4 The condensation of diketones with primary amines constitutes a very useful method for generating pyrroles. This reaction is called the Paal-Knorr condensation, [5][6][7] and is described in Scheme 1.…”

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confidence: 99%

Extensive rearrangement reactions observed for differently N-substituted 2,5-dimethylpyrroles under electron ionization

Joutsiniemi

Leppälä

Vainiotalo

1998

Rapid Commun. Mass Spectrom.

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The 70 eV electron ionization mass spectra of fourteen differently N-substituted 2,5-dimethylpyrroles were studied. In accord with the aromatic character of the pyrrole ring, all the compounds studied gave rise to an intense molecular ion peak. Regardless of the functional group at the 1-substituent, for all the compounds the principal fragmentation products were practically the same, although the relative peak intensities varied depending on the structure of the substituent. In addition, an amino group substituent prompted intense radical site initiated cleavages which were minor or totally absent with other compounds. The data showed that extensive rearrangement reactions took place. Some of these were seen directly from the mass spectra, and some only from closer examination of the ion structures. The structures of the ions at m/z 108 and 94, formally representing the [MÀ1]ions of 1,2,5-trimethylpyrrole and 2,5-dimethylpyrrole, respectively, were carefully studied using the collision induced dissociation (CID) technique. Measurements showed that ring expansion reactions took place, protonated 2,5-lutidine and protonated 2-picoline being the most likely isomers formed for the m/z 108 and 94 ions, respectively. The results obtained from the CID experiments were supported by semi-empirical calculations of heats of formation. # 1998 John Wiley & Sons, Ltd. Received 22 December 1997; Revised 5 January 1998; Accepted 10 January 1998 Rapid Commun. Mass Spectrom. 12, 231-238 (1998 A pyrrole ring is a part of many important biologically active compounds.1,2 In fact, some polysubstituted pyrroles have even been reported to have various biological and pharmaceutical activities.3,4 The condensation of diketones with primary amines constitutes a very useful method for generating pyrroles. This reaction is called the Paal-Knorr condensation, 5-7 and is described in Scheme 1.Unsubstituted pyrrole and its relatively simple alkylsubstituted derivatives have been studied by mass spectrometry to some extent. [8][9][10][11] In the present work, we synthesized fourteen differently N-substituted 2,5-dimethylpyrroles (listed below), by the Paal-Knorr condensation from 2,5-hexanedione and appropriate primary amines.The mass spectrometric behaviour of these compounds was studied under electron ionization. The main intention was to find the most important fragmentation routes of Nsubstituted pyrroles and the possible dependence of the fragmentation pathways and the nature of the substituent. The fragmentation routes were verified by exact mass measurements, metastable ion analysis and collision induced dissociation (CID) techniques. The spectra observed directly showed that several rearrangements take place. It is also known from the work of Glish et al.9 that ring expansion reactions are common with dimethylpyrroles. For these reasons, some detailed ion structural studies were carried out for long-lived ions generated from compounds 12 and 13, using a low energy CID technique. Heat of formation values were also calculated by a semiem...

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“…This is commonly referred to as the Paal-Knorr reaction. 11,12 The limited availability of different 1,4-diketones and the requirement for a strong acid are both limitations of this procedure. Accordingly, one-pot procedures for the synthesis of furans via the metal-catalyzed formation of 1,4-diketone intermediates have been developed.…”

Section: Synthesis Of Disubstituted Furansmentioning

confidence: 99%