Carbonylnitrenes, insertion

It appears that carbonylnitrenes insert at a detectable rate only in their singlet states, while phenylnitrene and cyanonitrene can insert in both their singlet and triplet states. Also, activated C—bonds (such as aromatic C—bonds or those next to ether linkages) may react with triplet carbonylnitrenes . ... 

The yields of the isocyanates produced upon photolysis of benzoyl azide (R=Ph, 31b) and its pam-methoxy, para-chloro and meta- uoro derivatives were found to be in the range of 40-50% in both inert solvents and in solvents that intercept acylnitrenes. Similar results were obtained for 2-naphthoyl azide (35). Irradiation of 35 in cyclohexane at room temperature produces isocyanate (36, -45%), A-cyclohexyl-2-naphthamide - the product of 2-naphthoylnitrene (37) insertion (-50%), and a trace (<1%) of 2-naphthamide (38). Therefore, it was concluded that carbonylnitrenes (R-CO-N) do not rearrange to isocyanates (R-N=C=0) at a rate that is competitive with their capture by trapping agents. ... 

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