Photochemical and Thermal Transformations of 1-Aryloxy-2- and 4-Azidoanthraquinones

The photolysis of 1-aryloxy-2-azidoanthraquinones (3) in benzene is described herein which gave 1-hydroxy-2-arylaminoanthraquinones (4) and two types of 5H-naphtho[2,3-c]phenoxazine-8,13-diones (5 and 6). Thermolysis of 3 yielded only one of phenoxazines 5 and small amount of 4. On the other hand thermolysis of 3 in the presence of phenols gave phenoxazine 6 as a major product. The mechanism of the photolysis and thermolysis of 2-azido-1-aryloxyanthraquinones (3) is proposed and supported by the results from semiempirical calculations. A relative contribution of the primary photoreactions-azido group dissociation and aryl group migration was estimated to be 3:1. Photolysis and thermolysis of 4-azido-1-(p-tert-butylphenoxy)-9,10-anthraquinone (8) gave 3-(p-tert-butylphenoxy)-anthra[1,9-cd]-izoxazole-6-one (9) as the only product.