On the Bromination of Diethyl 3,5-dimethyl-1H-pyrrole-2,4-dicarboxylate: the True Structure of the Halbig’s Product
Salkeyeva L.K. Pevzner L.M. Vojtíšek P. Minayeva Y.V.
2024E.A. Buketov Karaganda University Publish house
Eurasian Journal of Chemistry
2024#29Issue 114 - 23 pp.
Pyrrole and its derivatives have attracted the attention of researchers as promising objects of practical importance in various areas of human life. Focusing on Knorr pyrrole as the most readily available pyrrole derivative, our objective was to obtain its bromo derivatives, containing an allyl bromine atom followed by phosphorylation reactions. The reaction involving bromination was carried out with 2 mol of Nbromosuccinimide per 1 mol of Knorr pyrrole 1 in carbon tetrachloride. This reaction was initiated with azobis(isobutyronitrile) and carried out at a boiling point. In acetic acid, the bromination reaction was carried out at a temperature of 38‒45°C with a molar ratio of Knorr pyrrole to bromine of 1:4 and another reaction was carried out at 40‒50°C with a molar ratio of Knorr pyrrole to bromine of 1:5. The bromination reaction was also performed in chloroform at 27‒30°C in the presence of catalytic amounts of aluminum chloride. The same crystalline product was obtained in all cases. X-ray diffraction analysis revealed that the single crystal structure is diethyl 5-(dibromomethyl)-3-methyl-2-oxo-2,3-dihydro-1H-pyrrole-3,4-dicarboxylate 5 with two bromine atoms. This composition is identical to that of the Halbig product. It was found that the bromination of Knorr pyrrole 1 occurs stepwise with excess N-bromosuccinimide and bromine, resulting in the unsaturated lactam 5, commonly known as Halbig’s product. The true structure of product 5 was determined.
bromination , bromo derivatives , Diethyl 3,5-dimethyl-1H-pyrrole-2,4-dicarboxylate , Knorr pyrrole , phosphorylation , reaction mechanism , the Halbig’s product , α-methylpyrroles
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Department of Organic Chemistry and Polymers, Karaganda Buketov University, Universitetskaya str., 28, Karaganda, 100024, Kazakhstan
Department of Organic Chemistry, Saint Petersburg State Technological Institute (Technical University), Moskovsky prospect, 26, Saint Petersburg, 190013, Russian Federation
Jan Evangelista Purkyně University in Ústí nad Labem, Department of Chemistry, Faculty of Science, Pasteurova 3632/15, Ústí nad Labem, 400 96, Czech Republic
Department of Organic Chemistry and Polymers, Karaganda Buketov University, Karaganda, 100024, Kazakhstan
Department of Organic Chemistry and Polymers
Department of Organic Chemistry
Jan Evangelista Purkyně University in Ústí nad Labem
Department of Organic Chemistry and Polymers
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