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Fe(II)-Catalyzed Isomerization of 4‑Vinylisoxazoles into Pyrroles

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journal contribution
posted on 2017-07-20, 00:00 authored by Ekaterina E. Galenko, Vladimir A. Bodunov, Alexey V. Galenko, Mikhail S. Novikov, Alexander F. Khlebnikov
The first synthesis of pyrroles by Fe­(II)-catalyzed isomerization of 4-vinylisoxazoles is reported. 5-Alkoxy, amino, and N,N-dialkylamino-3-aryl/alkyl-4-(2-R-vinyl)­isoxazoles afford 2-aryl/alkyl-5-aryl/alkyl/methoxycarbonyl-1H-pyrrol-3-carboxylic acid derivatives typically under mild conditions with cheap and available FeCl2·4H2O as a catalyst. The isomerization of 5-alkoxy/amino-3-arylisoxazoles, bearing unsaturated carbo and heterocyclic substituents at the position 4, gives the corresponding fused pyrrolecarboxylic acid derivatives in high yields. DFT calculations were used to elucidate a probable mechanism of the isomerization and explain the influence of steric congestion of the vinyl moiety on the isomerization pathway.

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