Photochromism of 3H-2,1,4-benzoxadiazine 4-oxides with heterocyclic substituents on the benzene ring

Resumo

2H-Benzimidazole 1,3-dioxides undergo thermal isomerization to 3H-2,1,4-benzoxadiazine 4-oxides which are converted to 2H-benzimidazole 1-oxides on further heating. Irradiation of 3H-2,1,4-benzoxadiazine 4-oxides with sunlight induces their transformation to 2H-benzimidazole 1,3-dioxides. 3H-2,1,4-Benzoxadiazine 4-oxides containing nucleophilic heterocyclic substituents are considerably more stable to sunlight, and they can be used as photochromic compounds.