Photoisomerization of Isatogens to Benzoxazin-4-ones

A mild photoinduced isomerization of isatogens to benzoxazin-4-ones is described. Upon irradiation at 370 nm, a broad range of 2-aryl- and 2-alkyl-substituted isatogens undergo efficient scaffold reorganization under catalyst-free conditions to afford benzoxazin-4-ones in good to excellent yields. The transformation tolerates diverse substitution patterns, including heteroaryl and strained alkyl groups, and is readily scalable. Mechanistic experiments support participation of an excited-state pathway, and inclusion of catalytic 2-picolinic acid provided reproducible outcomes. For a nitro-substituted substrate, a distinct reaction pathway is observed, leading to the formation of a toluene-derived adduct. These results establish isatogens as versatile photochemical precursors to benzoxazinone scaffolds under operationally simple conditions.

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