Nitrenes alkylnitrenes

In fact, rearrangements of singlet alkylnitrenes generated in frozen matrices cannot even be suppressed by developing strain in imine products such as 1-3, although some triplet nitrene is detected by EPR and UV-vis spectroscopy upon low-temperature photolysis of 1-azidonorbornane. ... 

G. Nitrenes.—The importance of nitrenes is well known,128 and the prototype NH has been extensively studied in the past,129 but until recently no ab initio work has appeared on other nitrenes. The simplest alkylnitrene, MeN, has not been studied spectroscopically but three recent papers have investigated the ground state and some excited states.11 130 131... 

Since there is no evidence of nitrene intermediates in the solution photochemistry of alkyl azides, attempts were made to detect triplet alkylnitrenes in matrix photochemical experiments. Photolysis of CH3N3 or CD3N3 at cryogenic temperatures in Ar, N2 and CO2 matrices fails to produce an IR spectrum attributable to triplet methylnitrene. The IR spectrum of imine CH2=NH (or CD2=ND) is observed instead. 

Therefore, no experimental data is available which indicates formation of singlet alkyl-nitrenes as discrete intermediates upon photolysis of alkyl azides with the exception of perfluorinated alkylnitrenes. There is also doubt that MeN is a true intermediate, namely, a species which is characterized by a minimum on the potential energy surface (PES). To investigate this issue a series of quantum chemical calculations were performed ... 

Intramolecular insertion and addition reactions are almost unknown for alkylnitrenes. In fact, it is not clear that the nitrenes are formed as discrete species. The migration may be concerted with elimination, as in the case of the Wolff rearrangement. 

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