- An improved method for the preparation of N-unsubstituted 1,4,5,6-tetrahydrocyclopenta[b]pyrroles: Synthesis of an azaprostacyclin analogue and its 7-cyano derivative
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Paal-Knorr cyclization of 2-acetonylcyclopentanone derivatives can be carried out most efficiently by reaction with hexamethyldisilazane (HMDS) when the reagents are previously adsorbed on alumina. By this procedure, the unstable pyrroloprostacyclin derivative rac-6a has been synthesized in 66% yield from racemic 6-oxoprostaglandin E1 (rac)-5b. In order to obtain less sensitive pyrroloprostacyclin derivatives, rac-6a has been transformed into the stable nitriles rac-7a and rac-7b by cyanation of the pyrrole ring with chlorosulfonyl isocyanate in the presence of triethylamine and subsequent cleavage of the protecting groups, respectively.
- Rousseau, Brigitte,Nydegger, Fredy,Gossauer, Albert,Bennua-Skalmowski, Baerbel,Vorbrueggen, Helmut
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Read Online
- An expeditious and highly efficient synthesis of substituted pyrroles using a low melting deep eutectic mixture
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An expeditious green method for the synthesis of diverse valued substituted pyrroles through a Paal-Knorr condensation reaction, using a variety of amines and 2,5-hexanedione/2,5-dimethoxytetrahydrofuran in the presence of a low melting mixture ofN,N’-dimethylurea andL-(+)-tartaric acid (which acts as a dual catalyst/solvent system), has fruitfully been revealed. Herein, we have disclosed the applicability of this simple yet effective strategy for the generation of mono- and dipyrroles in good to excellent yields. Moreover,C3-symmetric tripyrrolo-truxene derivatives have also been assembled by means of cyclotrimerization, Paal-Knorr and Clauson-Kaas reactions as crucial steps. Interestingly, the melting mixture was recovered and reused with only a gradual decrease in the catalytic activity (over four cycles) without any significant drop in the yield of the product. This particular methodology is simple, rapid, environmental friendly, and high yielding for the generation of a variety of pyrroles. To the best of our knowledge, the present work reveals the fastest greener method reported up to this date for the construction of substituted pyrroles by utilizing the Paal-Knorr synthetic protocol, achieving impressive yields under operationally simple reaction conditions without involving any precarious/dangerous catalysts or unsafe volatile organic solvents.
- Alvi, Shakeel,Ali, Rashid
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p. 9732 - 9745
(2021/12/01)
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- Thermal Behavior Analysis of Two Synthesized Flavor Precursors of N-alkylpyrrole Derivatives
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To expand the library of pyrrole-containing flavor precursors, two new flavor precursors—methyl N-benzyl-2-methyl-5-formylpyrrole-3-carboxylate (NBMF) and methyl N-butyl-2-methyl-5-formylpyrrole-3-carboxylate (NUMF)—were synthesized by cyclization, oxidation, and alkylation reactions. Thermogravimetry (TG), differential scanning calorimeter, and pyrolysis–gas chromatography/mass spectrometry were utilized to analyze the thermal degradation behavior and thermal degradation products of NBMF and NUMF. The TG-DTG curve indicated that the maximum mass loss rates of NBMF and NUMF appear at 310 and 268°C, respectively. The largest peaks of NBMF and NUMF showed by the differential scanning calorimeter curve were 315 and 274°C, respectively. Pyrolysis–gas chromatography/mass spectrometry detected small molecule fragrance compounds appeared during thermal degradation, such as 2-methylpyrrole, 1-methylpyrrole-2-carboxylic acid methyl ester, limonene, and methyl formate. Finally, the thermal degradation mechanism of NBMF and NUMF was discussed, which provided a theoretical basis for their application in tobacco flavoring additives.
- Ai, Lvye,Liu, Mengzhen,Ji, Xiaoming,Lai, Miao,Zhao, Mingqin,Ren, Tianbao
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p. 2389 - 2397
(2019/08/01)
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- Synthesis of gamma dicarbonyl and pyrrole compounds
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The present invention discloses processes for producing γ-dicarbonyl compounds by contacting an aldehyde compound, an α,β-unsaturated carbonyl compound, and a catalyst composition in the presence of an amide diluent. The resultant γ-dicarbonyl compounds then can be used to synthesize pyrrole compounds, such as 2,5-dimethylpyrrole.
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Page/Page column 19
(2019/03/01)
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- Acceptorless Dehydrogenative Coupling Using Ammonia: Direct Synthesis of N-Heteroaromatics from Diols Catalyzed by Ruthenium
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The synthesis of N-heteroaromatic compounds via an acceptorless dehydrogenative coupling process involving direct use of ammonia as the nitrogen source was explored. We report the synthesis of pyrazine derivatives from 1,2-diols and the synthesis of N-substituted pyrroles by a multicomponent dehydrogenative coupling of 1,4-diols and primary alcohols with ammonia. The acridine-based Ru-pincer complex 1 is an effective catalyst for these transformations, in which the acridine backbone is converted to an anionic dearomatized PNP-pincer ligand framework.
- Daw, Prosenjit,Ben-David, Yehoshoa,Milstein, David
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supporting information
p. 11931 - 11934
(2018/09/27)
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- Direct Synthesis of Pyrroles via Heterogeneous Catalytic Condensation of Anilines with Bioderived Furans
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Given the wide applications of pyrroles in agriculture, pharmaceuticals, and supramolecular and materials chemistry, a mild and eco-friendly route to produce functionalized pyrroles from bioderived feedstocks is highly desirable. Described herein is a mild and convenient synthesis of pyrroles via direct condensation of an equimolar amount of structurally diverse anilines with biobased furans catalyzed by a simple and efficient solid acid H form zeolite Y catalyst. The protocol tolerates a large variety of functional groups and offers a general and versatile method for scale-up synthesis of a variety of N-substituted pyrrole compounds. Most importantly, the bioactive pyrrole-derived drug pyrvinium, which has lately been confirmed as highly effective in curing colon cancer, can be obtained by this method.
- Tao, Lei,Wang, Zi-Jian,Yan, Tian-Hao,Liu, Yong-Mei,He, He-Yong,Cao, Yong
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p. 959 - 964
(2017/08/09)
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- Indium-Catalyzed Formal N-Arylation and N-Alkylation of Pyrroles with Amines
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Under indium Lewis acid catalysis, a nitrogen atom of N-unsubstituted pyrroles was replaced with a nitrogen atom of primary amines, thereby producing N-aryl- and N-alkylpyrroles. This system formally introducing such carbon frameworks to the pyrrole nitrogen atom shows unique selectivity: only the H?N(pyrrolyl) unit undergoes the N-arylation and N-alkylation even in the coexistence of a similar H?N(indolyl) part; and an aryl–halogen bond remains intact. These are clearly different from the typical method depending on the C?N(pyrrolyl) bond-forming reaction with organic halides as substrates. From a viewpoint of pyrrole N-protection–deprotection chemistry, worth noting is that a methyl group on the pyrrole nitrogen atom can be removed, albeit in a formal way. (Figure presented.).
- Yonekura, Kyohei,Oki, Kenji,Tsuchimoto, Teruhisa
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supporting information
p. 2895 - 2902
(2016/09/16)
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- The Paal-Knorr reaction revisited. A catalyst and solvent-free synthesis of underivatized and N-substituted pyrroles
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A new, modified synthesis of pyrroles is described. The reaction of 2,5-hexandione with a variety of amines yielded the expected pyrrole analogues in excellent yields. The reactions were carried out under the ultimate green conditions excluding both catalyst and solvent applying simple stirring at room temperature. The variety of amines include aqueous ammonium hydroxide for the synthesis of pyrroles with a free NH group, and benzylamines, anilines and phenylene-diamines for the synthesis of several N-derivatized pyrroles. The reaction also occurs efficiently with a variety of 1,4-diketones, although the reaction rates and yields are lower for the diketones that do not possess terminal methyl group(s). This journal is
- Cho, Hyejin,Madden, Richard,Nisanci, Bilal,T?r?k, Bla
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p. 1088 - 1099
(2015/03/04)
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- METHODS FOR THE CONVERSION OF A SUBSTITUTED FURAN TO A SUBSTITUTED PYRROLE
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The present invention discloses processes for producing substituted pyrrole compounds, such as 2,5-disubstituted pyrroles. Synthetic processes which directly convert substituted furan compounds to substituted pyrrole compounds, via a reaction of the substituted furan compound with ammonia and/or an ammonium salt in the presence of a catalyst, also are described.
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Page/Page column 21
(2012/04/11)
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- Flow synthesis using gaseous ammonia in a Teflon AF-2400 tube-in-tube reactor: Paal-Knorr pyrrole formation and gas concentration measurement by inline flow titration
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Using a simple and accessible Teflon AF-2400 based tube-in-tube reactor, a series of pyrroles were synthesised in flow using the Paal-Knorr reaction of 1,4-diketones with gaseous ammonia. An inline flow titration technique allowed measurement of the ammonia concentration and its relationship to residence time and temperature.
- Cranwell, Philippa B.,O'Brien, Matthew,Browne, Duncan L.,Koos, Peter,Polyzos, Anastasios,Pe?a-López, Miguel,Ley, Steven V.
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scheme or table
p. 5774 - 5779
(2012/08/28)
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- PROCESSES FOR THE SYNTHESIS OF GAMMA NITROCARBONYL AND GAMMA DICARBONYL COMPOUNDS AND THEIR PYRROLE DERIVATIVES
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The present invention discloses processes for producing γ-nitrocarbonyl and γ-dicarbonyl compounds, which can be precursors in the synthesis of pyrrole compounds. A process for producing pyrroles such as 2,5-dimethylpyrrole, and structurally similar pyrrole compounds, is also disclosed.
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Page/Page column 15
(2010/10/19)
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- GOLD CATALYZED HYDROAMINATION OF ALKYNES AND ALLENES
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Methods are provided for the catalytic hydroamination of compounds having an alkyne or allene functional group, in which the compound is contacted with ammonia or an amine in the presence of a catalytic amount of a gold complex under conditions sufficient for hydroamination to occur.
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Page/Page column 21; 2/13
(2010/01/29)
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- Homogeneous catalytic hydroamination of alkynes and allenes with ammonia
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(Chemical Equation Presented) A golden ticket to the synthesis of reactive nitrogen-containing compounds, such as imines, enamines, and allyl amines, through the addition of NH3 to unsaturated bonds is the cationic cyclic (alkyl)-(amino)carbene-gold(I) catalyst shown in blue (Dipp=diisopropylphenyl). An ideal initial step for the preparation of simple bulk chemicals, this reaction is also useful for the synthesis of more complex molecules (see examples).
- Lavallo, Vincent,Frey, Guido D.,Donnadieu, Bruno,Soleilhavoup, Michele,Bertrand, Guy
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experimental part
p. 5224 - 5228
(2009/04/11)
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- New method for the synthesis of 2-aza-1,3-butadienes
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2-Aza-1,3-butadienes have been synthesized from carbonyl compounds and 1,1,1,3,3,3-hexamethyl-disilazane in the presence of cobalt-containing catalysts. The best yields (up to 95%) were achieved in the case of aldehydes branched in the α-position and 2-methylcyclohexanone. In the case of two α,β-unsaturated ketones, pyridine derivatives were found as the main products. Copyright Taylor & Francis Group, LLC.
- Sisak, Attila
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p. 3693 - 3702
(2007/10/03)
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- o-Iodoxybenzoic Acid (IBX) as a Viable Reagent in the Manipulation of Nitrogen- and Sulfur-Containing Substrates: Scope, Generality, and Mechanism of IBX-Mediated Amine Oxidations and Dithiane Deprotections
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o-Iodoxybenzoic acid (IBX), a highly versatile hypervalent iodine(V) reagent, was found to efficiently mediate the dehydrogenation of amines in addition to facilitating the oxidative cleavage of dithioacetals and dithioketals. Through the development of relevant IBX-based protocols, a plethora of useful synthetic intermediates, including imines, oximes, ketones, and aromatic N-heterocycles, were found to be readily accessible under notably mild conditions. Further investigation of these transformations led to the elucidation of valuable mechanistic details, resulting in the conclusion that they proceed via ionic rather than single electron transfer (SET) pathways.
- Nicolaou,Mathison, Casey J. N.,Montagnon, Tamsyn
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p. 5192 - 5201
(2007/10/03)
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- A novel facile synthesis of 2,5-di- and 2,3,5-trisubstituted pyrroles
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Heterocyclization of ketoximes with propyne or allene in superbase systems MOR/DMSO (M = K, Cs; R = H, t-Bu), which leads to 2-alkyl(aryl, hetaryl)-5-methyl- and 2,3-dialkyl-5-methylpyrroles or 2-methyl-4,5,6,7-tetrahydroindole in yields of up to 63%, has been accomplished for the first time. The reaction is mostly regioselective affording mainly or exclusively 2,5-di- and 2,3,5-trisubstituted pyrroles. The minor isomers in most cases are the corresponding 2,4-di- and 2,3,4-trisubstituted pyrroles, only in the case of acetoxime the isomer ratio is ca 1:1. For oximes of methyl isopropyl ketone and pinacolone, the 4-methyl-isomers become predominant (78, 83%, respectively).
- Trofimov,Tarasova,Mikhaleva,Kalinina,Sinegovskaya,Henkelmann
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p. 1585 - 1590
(2007/10/03)
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- Concerted rotation in a tertiary aromatic amide: Towards a simple molecular gear
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At least 90% of the rotations about the Ar-CO bond in amide 1 are concerted with rotation about the C-N bond. As a result, 1 demonstrates features of a simple molecular gear.
- Clayden, Jonathan,Pink, Jennifer H.
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p. 1937 - 1939
(2007/10/03)
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- An Electron Spin Resonance Study of the Radical Cations of Pyrroles, Furans, and Thiophenes in Liquid Solution
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Photolysis of alkylpyrroles in trifluoroacetic acid containing mercury(II) trifluoroacetate, alkylfurans in trifluoroacetic acid, or alkylthiophenes in sulphuric acid, induces oxidation to the corresponding radical cations.The e.s.r. spectra show that the electronic configuration is similar in all three species, the unpaired electron occupying the φA MO in which the heteroatom lies in a nodal plane.Photolysis of 2,6-dimethyl- and 2,6-diethyl-thiophene in trifluoroacetic acid containing mercury(II) trifluoroacetate, on the other hand, gave rise to spectra with a high g value (2.0062), showing hyperfine coupling to two non-equivalent pairs of alkyl groups in an unsymmetrical dimer.
- Davies, Alwyn G.,Julia, Luis,Yazdi, Safieh N.
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p. 239 - 244
(2007/10/02)
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- THE SYNTHESIS AND CHEMISTRY OF AZOLENINES. PART 12. ISOLATION OF INTERMEDIATE 2-HYDROXY-3,4-DIHYDRO-2H-PYRROLES IN THE PAAL-KNORR 1H-PYRROLE SYNTHESIS.
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Treatment of 1,4-diketones with liquid ammonia gives high yields of isolable 2-hydroxy-3,4-dihydro-2H-pyrrole intermediates.These intermediates, which do not appear to have been observed previously in the Paal-Knorr synthesis with ammonia, have been fully characterized by i.r. and 1H and 13C n.m.r. spectroscopy; in most cases they decompose quantitatively into 1H-pyrroles on standing.The intermediate from hexane-2,4-dione may also be prepared using concentrated aqueous ammonia.
- Chiu, Pak-Kan,Sammes, Michael P.
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p. 3531 - 3538
(2007/10/02)
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- DISILYLATED COMPOUNDS AS PRECURSORS OF HETEROCYCLES: SYNTHESIS OF BENZIMIDAZOLES, TRIAZOLES, FURAN AND PYRROLE.
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The cyclization of disilylated compounds catalyzed by trifluoromethanesulfonoc acid is an easy way to obtain some heterocycles such as benzimidazole, triazole, furan and pyrrole.
- Rigo, Benoit,Valligny, Dominique,Taisne, Sophie
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p. 167 - 180
(2007/10/02)
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- Novel Synthesis of 3H-Pyrroles, and Novel Intermediates in the Paal-Knorr 1H-Pyrrole Synthesis: 2-Hydroxy-3,4-dihydro-2H-pyrroles from 1,4-Diketones and Liquid Ammonia
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Reaction of 2,2-dimethyl-1,4-diketones with liquid ammonia gives high yields of isolable 2-hydroxy-3,4-dihydro-2H-pyrroles (3) and (5) which are readily dehydrated to give separable mixtures of 3H-pyrroles and methylenedihydropyrroles, while less-substituted 1,4-diketones give analogous hydroxy-compounds (4) and (6) which are hitherto-unsuspected intermediates in the Paal-Knorr 1H-pyrrole synthesis.
- Chiu, Pak-Kan,Lui, Kon-Hung,Maini, Prem Nath,Sammes, Michael P.
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p. 109 - 110
(2007/10/02)
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- The Electron Spin Resonance Spectra of the Radical Cations of Furans, Thiophenes, and Pyrroles in Liquid Solution
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The radical cations of various furans, thiophenes, and pyrroles have been generated in fluid solution and characterised by e.s.r. spectroscopy.
- Davies, Alwyn G.,Julia, Luis,Yazdi, Safieh N.
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p. 929 - 930
(2007/10/02)
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- Maillard Reaction Products Formed from D-Glucose and Glycine and the Formation Mechanisms of Amides as Major Components
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Equimolar aqueous solution of D-glucose and glycine were heated at 50 oC and 95 oC at pH 6.7.The headspace volatiles and the ether extracts from the reaction mixture were analyzed by gaz chromatography and gas chromatography-mass spectrometry, using a fused silica capillary column.The major components formed were identified as diacetyl, furfuryl alcohol, two pyrroles, one pyranone and two amides.In order to elucidate the formation mechanisms of the amides formed from amino-carbonyl reactions, two model systems were adopted.N-Butylacetamide and N-butylformamide were formed as major components from diacetyl-butylamine and glyoxal- butylamine systems, respectively.The results obtained suggest that such α-dicarbonyls as 3-deoxyosone, 1-deoxy-D-erythro-2,3-hexodiulose and diacetyl generated in the amino-carbonyl reaction react with amino compounds, amides then formed by cleavage of the C-C bond in the α-dicarbonyls.
- Hayase, Fumikata,Kim, Bong Seon,Kato, Hiromichi
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p. 2337 - 2342
(2007/10/02)
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- 4-Alkylideneisoxazol-5-ones. Synthesis, Tautomerism, and Rearrangement to Pyrroles
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The synthesis of several 4-alkylidene- and 4-cycloalkylideneisoxazol-5-ones is described and their tautomerism is investigated by 13C NMR, 1H NMR and IR spectroscopy.Through hydrogen shifts involving the exocyclic substituent (2-propylidene, cyclopentylidene, or 2-indanylidene) these compounds can exist in CH, NH, or OH forms (Scheme II).The CH form is favored in solvents of low polarity (CDCl3) and in the absence of special enthalpic and conjugative effects stabilizing the NH form.The NH form is favored in polar solvents (Me2SO), and its dominance is accentuated when the vinylic substituent is stabilized thermodynamically and conjugationally.The OH form is not observed directly, but the ionized O- form is present in the morpholinium salts of 15, 16, and 17.In the 2-propylidene derivative 12 only the CH form was spectroscopically detectable, but H/D exchange experiments on this and other isoxazolones showed that tautomerism does take place (12 * 24).The alkylideneisoxazolones rearrange to pyrrolecarboxylic acids on flash vacuum pyrolysis.Of two possible mechanisms, a vinylnitrene mechanism (Scheme IV) and a nitrile ylide mechanism (Scheme V), the former is shown to apply.The pyrrolecarboxylic acids often decarboxylate under the reaction conditions.
- Wollweber, Hans-Joachim,Wentrup, Curt
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p. 2041 - 2047
(2007/10/02)
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- A General Synthesis of Pyrroles from Aldehydes and Ketones
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The azines of enolisable aldehydes and ketones are converted into pyrroles via thermal rearrangement of the derived benzoyl derivatives and subsequent hydrazinolysis of the resulting N-benzoylpyrroles.
- Baldwin, Jack E.,Bottaro, Jeffrey C.
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p. 624 - 625
(2007/10/02)
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- Synthetic Applications of N-N Linked Heterocycles. Part 10. Preparation of Novel N-N Linked Biheteroaryl Monocations, their Reactions with Nucleophiles, and Electrophilic Reactions of some Dihydro-derivatives
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Novel N-N linked biheteroaryl monocations are prepared from N-aminopyridinium, -quinolinium, or -isoquinolinium salts, with dehydroacetic acid, cyclic anhydrides, hexane-2,4-dione, or the benzoxazinone (15).Reactions of dihydro-derivatives (from reduction of the cations with sodium borohydride or sodium dithionite) with electrophiles are investigated.Reactivity towards nucleophiles was studied to evaluate, (a) the regioselectivity of nucleophilic addition, and (b) the ease of decomposition of the resulting adducts into 4-substituted pyridines.
- Katritzky, Alan R.,Ibrahim, M. Hussain,Valnot, Jean-Yves,Sammes, Michael P.
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p. 859 - 881
(2007/10/02)
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