2-(1H-Pyrazol-1-ylcarbonyl)-2H-azirines were synthesized by in situ trapping of 2H-azirine-2-carbonyl chlorides, generated by Fe(II)-catalyzed isomerization of 5-chloroisoxazoles, with pyrazoles. According to DFT calculations, the selectivity of nucleophilic substitution at the carbonyl group of 2H-azirine-2-carbonyl chloride by a pyrazole nucleophile, which is a mixture of two tautomers, is controlled by thermodynamic factors. 2-(1H-Pyrazol-1-ylcarbonyl)-2H-azirines are excellent precursors for the preparation of two other pyrazole-nitrogen heterocycle dyads: 5-(1H-pyrazol-1-yl)oxazoles by photolysis and 1-(1H-pyrrol-2-ylcarbonyl)-1H-pyrazoles by a Ni(II)-catalyzed reaction with 1,3-dicarbonyl compounds. 5-(1H-Pyrazol-1-yl)oxazoles show strong emission in acetonitrile at 360-410 nm with high quantum yields.
CITATION STYLE
Mikhailov, K. I., Galenko, E. E., Galenko, A. V., Novikov, M. S., Ivanov, A. Y., Starova, G. L., & Khlebnikov, A. F. (2018). Fe(II)-Catalyzed Isomerization of 5-Chloroisoxazoles to 2 H -Azirine-2-carbonyl Chlorides as a Key Stage in the Synthesis of Pyrazole-Nitrogen Heterocycle Dyads. Journal of Organic Chemistry, 83(6), 3177–3187. https://doi.org/10.1021/acs.joc.8b00069
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