Under light irradiation, a reaction of N ‐(2‐(prop‐1‐en‐2‐yl)phenyl)benzamides, thianthrenium salts and sodium hydrogen sulfite under copper catalysis and photocatalysis is developed. Diverse sulfonated benzo d 1,3oxazines are generated in good yields with broad functional group tolerance by using sodium hydrogen sulfite as the sulfur dioxide surrogate. During the reaction process, a radical pathway with the insertion of sulfur dioxide is proposed.
Chen et al. (2025) studied this question.