Photochemical conversions of selected benzazides and azidoquinoneimines

Irradiation [lamda >315 nm, using high-pressure lamp HPK 125 W] of toluene solutions of phthalimidobenzazides 3a, b, and benzazides 4a, b effect a photo- Curtius rearrangement yielding the symmetrical ureas 7a,b and 11a,b, respectively, most likely via the corresponding acylnitrenes which rearrange to the isocyanates. Under similar conditions, 2-azido- and 2,5- diazido-1,4-benzoquinonedi- [benzene sulfonylimines] 5 and 6 produced the triazolo derivatives 12 and 14, respectively. When a solution of azide 5 in dry toluene inside a sealed tube was irradiated with natural sunlight, the diametric triazolo derivative 15 was formed