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ACID-CATALYZED REARRANGEMENT OF 1-ACYL-2-AZABUTA-1,3-DIENES TO 4-PYRROLIN-2-ONES

Николай В. Ростовский, Илья А. Сметанин, Александр Н. Коронатов, Анастасия В. Агафонова, Василий В. Потапенков, Александр Ф. Хлебников, Михаил С. Новиков
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Abstract


1-Acyl-2-azabuta-1,3-dienes underwent rearrangement to 4-pyrrolin-2-ones in the presence of acidic catalysts (silica gel or ZnCl2) and water. The reaction proceeded via the formation of 2,3-dihydroxy-3,4-dihydropyrrole and 2-hydroxy-2Н-pyrrole intermediates, the latter of which was transformed by [1,5]-sigmatropic shift of carbonyl substituent and prototropic isomerization. 4-Chloro-substituted 1-acetyl-2-azabuta-1,3-dienes were stable toward rearrangement, while brominated analogs rearranged into 4-pyrrolin-2-ones, probably as a result of the initial radical hydrodebromination. According to calculations performed at the DFT level, two steps of the reaction were catalyzed by acid: the cyclization of 2-azabutadiene and the sigmatropic shift in the 2-hydroxy-2Н-pyrrole intermediate.

Authors: Nikolai V. Rostovskii, Ilia A. Smetanin, Alexander N. Koronatov, Anastasiya V. Agafonova, Vasilii V. Potapenkov, Alexander F. Khlebnikov, Mikhail S. Novikov*


Keywords


azabuta-1,3-dienes; pyrrolinones; acid catalysis; sigmatropic shift

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