10.1021/acs.joc.8b00069.s001 Kirill I. Mikhailov Kirill I. Mikhailov Ekaterina E. Galenko Ekaterina E. Galenko Alexey V. Galenko Alexey V. Galenko Mikhail S. Novikov Mikhail S. Novikov Alexander Yu. Ivanov Alexander Yu. Ivanov Galina L. Starova Galina L. Starova Alexander F. Khlebnikov Alexander F. Khlebnikov Fe(II)-Catalyzed Isomerization of 5‑Chloroisoxazoles to 2<i>H</i>‑Azirine-2-carbonyl Chlorides as a Key Stage in the Synthesis of Pyrazole–Nitrogen Heterocycle Dyads American Chemical Society 2018 2 H Pyrazol -1-ylcarbonyl H azirine -2-carbonyl chlorides pyrrol -2-ylcarbonyl H Fe DFT azirine -2-carbonyl chloride Pyrazol -1-yl show pyrazole 2018-02-15 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Fe_II_-Catalyzed_Isomerization_of_5_Chloroisoxazoles_to_2_i_H_i_Azirine-2-carbonyl_Chlorides_as_a_Key_Stage_in_the_Synthesis_of_Pyrazole_Nitrogen_Heterocycle_Dyads/5936164 2-(1<i>H</i>-Pyrazol-1-ylcarbonyl)-2<i>H</i>-azirines were synthesized by in situ trapping of 2<i>H</i>-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 2<i>H</i>-azirine-2-carbonyl chloride by a pyrazole nucleophile, which is a mixture of two tautomers, is controlled by thermodynamic factors. 2-(1<i>H</i>-Pyrazol-1-ylcarbonyl)-2<i>H</i>-azirines are excellent precursors for the preparation of two other pyrazole–nitrogen heterocycle dyads: 5-(1<i>H</i>-pyrazol-1-yl)­oxazoles by photolysis and 1-(1<i>H</i>-pyrrol-2-ylcarbonyl)-1<i>H</i>-pyrazoles by a Ni­(II)-catalyzed reaction with 1,3-dicarbonyl compounds. 5-(1<i>H</i>-Pyrazol-1-yl)­oxazoles show strong emission in acetonitrile at 360–410 nm with high quantum yields.