Synthesis of 2‑Isoxazoline N‑Oxides by Copper-Mediated Radical Annulation of Alkenes with α‑Nitrobenzyl Bromides
journal contributionposted on 2020-09-16, 20:45 authored by Masayuki Iwasaki, Yuichi Ikemoto, Yasushi Nishihara
Copper-mediated [3 + 2] annulation of alkenes with α-nitrobenzyl bromides has been developed. The reaction is promoted simply by a copper salt to produce the corresponding 2-isoxazoline N-oxides with perfect regioselectivity. The present method can be conducted under mild conditions, affording a diverse array of 2-isoxazoline N-oxides. The obtained products can readily be converted to the related heterocycles such as 2-isoxazoline and isoxazole. A radical-polar crossover pathway initiated by single-electron transfer from nitronate to a copper salt is proposed.