Undesirable side reactions of aryl azides

The reaction products from aryl azides in photoaffinity labeling experiments have not been fully characterized. Indeed the reactions of aryl nitrenes in solution remain a topic of current research. 

A second cause of the relatively low reactivity of aryl nitrenes is the rearrangement of the singlet states to azacycloheptatetraenes or benzaziri-nes (Fig. 3.3 Chapman, 1979 Iddon et al., 1979 Colman et al., 1981  

Undesirable photochemical reactions occur with many aryl azides that have ortho substituents, which should be avoided. Intramolecular reaction of the nitrene results in wastage of the photogenerated intermediates, e.g. Fig. 3.4. 

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