136660-99-6Relevant articles and documents
Modified Paal-Knorr synthesis of novel and known pyrroles using tungstate sulfuric acid as a recyclable catalyst
Karami, Bahador,Jamshidi, Masih,Khodabakhshi, Saeed
, p. 12 - 16 (2013)
Tungstate sulfuric acid (TSA) as a solid acid catalyst has been synthesized and used in Paal-Knorr synthesis of some novel and known pyrroles under solvent-free conditions. Catalyst loadings can be as low as 1 mol percent to give high yields of the corresponding pyrroles at 60 °C. To make the catalyst, sodium tungstic reacted with chlorosulfonic acid in nhexane.
An EPR analysis of β-dimerization in α-blocked pyrroles in oxidant conditions
Julia, Luis,Rius, Jordi,Torrelles, Xavier
, p. 164 - 167 (2011)
Electron paramagnetic resonance (EPR) analysis of neutral and acidic solutions of 2,5-dimethyl-1-phenylpyrrol (1) and meta-, para-, and ortho-bis(2,5-dimethylpyrrol-1-yl)benzenes (4-6) in the presence of Tl(III) trifluoroacetate as oxidant reveals the poor stability of their generated monomeric radical cations which dimerize through C(β) i￡C(β) bond formation. EPR spectra of the monomeric radical cations 4?+, 5?+, and 6 ?+ coincide with that of 1?+, suggesting that the unpaired electron in these charged species is confined in one of the pyrrolic rings. The very twisted angles between pyrrolic and phenyl planes due to steric hindrance in the X-ray analysis of the molecular structure of 4 confirm the absence of extended conjugation in the π-system. Copyright
An expeditious and highly efficient synthesis of substituted pyrroles using a low melting deep eutectic mixture
Alvi, Shakeel,Ali, Rashid
, p. 9732 - 9745 (2021/12/01)
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.
Efficient synthesis of substituted pyrroles through Pd(OCOCF3)2-catalyzed reaction of 5-hexen-2-one with primary amines
Chen, Xi,Yang, Meng,Zhou, Min
supporting information, p. 5215 - 5218 (2016/11/11)
An efficient and facile Pd(OCOCF3)2-catalyzed one-pot cascade protocol has been developed for the synthesis of multiple substituted pyrroles in good to excellent yields. Unlike the reported method starting from the 2-alkenal-1,3-carbonyl compounds, the process utilizes the less reactive 5-hexen-2-one and the method has great potential as a complement to the current developed methods.
Greener Paal-Knorr Pyrrole Synthesis by Mechanical Activation
Akelis, Liudvikas,Rousseau, Jolanta,Juskenas, Robertas,Dodonova, Jelena,Rousseau, Cyril,Menuel, Stphane,Prevost, Dominique,Tumkeviius, Sigitas,Monflier, Eric,Hapiot, Frdric
, p. 31 - 35 (2016/01/20)
A straightforward and solventless synthesis of pyrroles was developed by using mechanochemical activation and a biosourced organic acid as the catalyst. Relative to traditional Paal-Knorr methodologies, various N-substituted pyrroles were obtained in very short reaction times. By reaction with unreactive diketones, desymmetrized aliphatic and aromatic compounds were also synthesized.
