Alkyl azides alkylnitrenes

Alkylnitrenes are very poor in functionalizing C—H bonds, even if the insertion is intramolecular. Earlier claims that pyrrolidines (6) could be formed by insertion of alkylnitrenes derived from simple alkyl azides have subsequently been disproved,and the only apparently genuine example of a reaction of this type involves the azidosteroid 6P-azido-5a-pregnane (7), which leads to functionalization of the... 

Most calculations available in the literature are concerned with the simplest alkyl azide and alkylnitrene, CH3-N3 (13) and CHg-N (14), respectively. The first ab initio theoretical study of the different electronic states of 14 was reported in 1974 by Yakony et al. The geometries of the lowest E, and electronic states of 14 were calculated at the self-consistent-field level of theory with a double basis set. The and states were predicted to lie 14,200 and 27,700 cm above the Ag ground state. Yakony et al. did not try to explain why 14 has been so difficult to isolate in the laboratory. ... 

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. 

The first experimental evidence for the existence of alkylnitrenes was provided by ESR spectroscopy in glassy matrixes. Very weak ESR signals were detected upon direct irradiation. Sensitized photolysis of alkyl azides was found to be the most appropriate procedure to generate triplet alkylnitrenes in glassy matrixes. ... 

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 ... 

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