Download full text in PDF Opens in a new window. Article suggestions will be shown in a dialog on return to ScienceDirect. ... Please enable JavaScript to use all the features on this page. ... The 3,7-diaryl-2H-imidazo[2,1-b][1,3,4]oxadiazines 1 in sunlight undergo a reversible transformation into mesoionic imidazole compounds 2. ... The 3,7-diaryl-2H-imidazo[2,1-b][1,3,4]oxadiazines (1) undergo by sunlight a reversible transformation into a mesoionic imidazo-compound ...