Photochemistry acyl azides

The parallel to the photochemistry of azides found in the arylimines is also observed on irradiation of 1,2,4-triazole 4-acyl-,129 133 4-sulfonyl-,81 and 4-carbamoylimines.133 In methanol the same products are generated as in the photolysis of the corresponding azides. Their formation is consistent with the mechanism given in Scheme 15 the AT-acyl- and sulfonyl-imines afford 1,2,4-triazole and a nitrene which yields the typical nitrene products 107a-d with methanol. Furthermore, carbamic esters (109) are formed, by addition of methanol to an isocyanate (108). These isocyanates can originate directly from the N-imine by a synchronous reaction or from the nitrene by a sextet rearrangement. Although irradiation of s-triazole... 

Abraham and co-workers investigated the photochemistry of acyl azides as a means of preparing acyl nitrenes (Scheme 1.158). They generated benzoyl nitrene from benzoyl azide in the presence of 2-butyne, 1,2-diphenylacetylene, and phenylacetylene and isolated 4,5-dimethyl-2-phenyloxazole 579, 2,4,5-triphenyl-oxazole 231c, and 2,5-diphenyloxazole 11, respectively, in 18-30% yield. The... 

The photochemistry of aryl azides is quite complex, suggesting that the nitrene 14 may not be the only reactive intermediate and that insertion reactions may not be the only route to form photoconjugates.Although aryl nitrenes are much less susceptible to rearrangements than acyl nitrenes, they may still occur and lead to the formation of reactive intermediates such as azepines, which may go on to react with nucleophiles.[911 141 Addition of nitrenes to double bonds will generate azirines, while dimerization will produce azobenzenesJ11 Aryl azides are stable to most of the procedures used in the course of peptide synthesis except for reduction reactions. Non-photochemical reduction of aryl azides to the primary amines by thiols has been reported by Staros et al.[15]... 

The photochemistry of 3-aryl-substituted l,4,2-dioxazol-2-in-5-ones (79) can be interpreted in terms of ring cleavage and loss of carbon dioxide with the formation of an acyl nitrene (80) such nitrenes are also formed by the photolysis of acid azides. In dimethyl sulfide, therefore, the 3-phenyl derivative itself (79 Ar=Ph) is converted into the photoproduct (81).05 When the phenyl group is substituted in... 

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