Acylnitrenes and Thio Analogs

Capozzi, V. Lucchini, G. Modena, and P. Scrimin, Tetrahedron Lett., 911 (1977). 

Acylnitrenes are formed by photolysis of acyl azides and react intramolec-ularly to form lactams.149 154 Evidence was adduced that it is a singlet nitrene which cyclizes to the lactam 108 on photolysis of the sulfilimine 107.155 Thermolysis gave only mesityl isocyanate (109).155 Isocyanates often,156 but not always157 accompany photolyses of acyl azides but generally this is thought to be a nonnitrene process (see below, however). 

Eibler and Sauer15 8 demonstrated with the aid of competition experiments that the same intermediate, in all likelihood the benzoylnitrene, was formed by photolysis of 110-112 (Eq. 34). Phenyl isocyanate was formed both thermally and photolytically from all three precursors, but no evidence for a nitrene was obtained under thermal conditions. 

Lwowski, in Nitrenes (W. Lwowski, ed), Chapter 6. Wiley (Interscience), New York, 1970. 

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