1- naphthyl azide, photochemistry

The photochemistry of naphthyl azides 79 and 80 in solution at ambient temperature has been studied using LFP ° and TRIR techniques and the femtosecond transient absorption spectroscopy. LFP study of naphthyl azide photochemistry in glassy solvents at 77 K has also been performed. ... 

In 1980 Dunkin and Thomson [84] studied the photochemistry of these azides by infrared spectroscopy. These workers photolyzed 1- and 2-naphthyl azides in argon at 10 K and observed the formation of several new IR bands between 1708 and 1736 cm 1 attributed to azirine type of species. Prolonged photolysis of the matrix isolated azirines isomerized these primary photoproducts to dehydroazepines which were observed by IR spectroscopy between 1911 and 1926 cm 1. 

With the assumption that the undetected precursors to triplet 1- and 2-naphthylnitrenes are the azirines seen in the low temperature experiments, we can reach useful conclusions about the photochemistry of polynuclear aromatic azides. First, unlike phenyl azide where the closed-shell singlet intermediate formed in room temperature irradiations is dehydroazepine [46, 49, 69], the intermediates formed from both 1- and 2-naphthyl azide are azirines. The difference in the chemistry of 1- and 2-naphthyl azides is traced to a difference in the lifetime of the respective azirines. The azirine from 2-naphthyl azide survives at least 200 times longer than does the azirine formed from 1-naphthyl azide. The increase in lifetime permits the bimolecular trapping reaction by diethylamine to compete with isomerization to the triplet nitrene in the case of the 2-naphthyl but not the 1-naphthyl azides. 

The discovery of the temperature dependence of the photochemistry of phenyl azide prompted Leyva and Platz [85] to reexamine the photochemistry of 1-naphthyl azide. As mentioned previously photolysis of 1-naphthyl azide at 298 K in the presence of diethylamine fails to produce an azepine adduct, instead only a trace of diamine 9 is observed along with small amounts of azonaphthalene [51, 57, 91], The major product is 1-naphthy-lamine. Carroll et al. [51] improved the yield of diamine adduct with piperidine by adding N, N, N, N tetramethylethylenediamine (TMEDA) to complex with singlet 1-naphthyl nitrene. TMEDA did not improve the yield of diethylamine adduct, however. 

Much effort has been devoted to the study of the photochemistry of 1- and 2-naphthyl azides (79 and 80). The products obtained upon pyrolysis and photolysis of the naphthyl azides were reported in the 1970s and In 1974, the Suschitzky group ... 

Scheme 11.46 Photochemistry of 1-naphthyl azide 79 in solution at ambient temperature...

The photochemistry of other polynuclear aromatic azide has been investigated in less detail than that of the naphthyl azides, althongh some azides have been studied to a certain extent. For instance, photolysis of 1-, 2-, and 9-azidoanthracenes in organic matrices at 77 K yields the corresponding triplet nitrenes, whose electronic absorption... 

Thus the results of a ns time resolved LFP study of 1-pyrenyl azide are very similar to that of 1-azidoanthracene. On the contrary, the photochemistry of 2-pyrenyl azide (101, Scheme 11.49) is quite similar to that observed for 2-naphthyl azide gO. Irradiation in benzene gives primarily 2,2 -azopyrene (102). In the presence of DEA (HNEta), the product is almost exclusively l-amino-2-diethylaminopyrene (103) and it reaches its maximum value at a very low concentration of DEA (4 x 10 M). ... 

Therefore, as in the case of parent phenyl azide 47 and its simple derivatives, the photochemistry of polynuclear aromatic azide, especially that of naphthyl azides 79 and 80, is now well understood. Specifically, the dynamics of the primary photophysical processes as well as the subsequent photochemical steps have been directly investigated using a variety of modem and conventional experimental techniques and compntational chemistry. It is clear now, that the difference between the photochemistry of phenyl azide (and its simple derivative) and polynuclear aromatic azide is caused mainly by the difference in the thermodynamics of the singlet nitrene rearrangement to azinine type species. 

J. Wang, J. Kubicki, G. Burdzinski, J.C. Hackett, T.L. Gustafson, C.M. Hadad, M.S. Platz, Early events in the photochemistry of 2-naphthyl azide from femtosecond UVWis spectroscopy and quantum chemical calculations Direct observation of a very short-lived singlet nitrene, J. Org. Chem., 2007, 72, 7581-7586. 

Leyva, E. and Platz, M. S., The temperature-dependent photochemistry of 1-naphthyl azide. Tetrahedron Lett., 28, 11, 1987. 

Comprehensive studies of the photochemistry of 2-naph-thoyl and substituted benzoyl azides were undertaken to determine the multiplicity of the ground state of aroylni-trenes. Irradiation (254 nm) of 2-naphthoyl azide (26) in cyclohexane at room temperature produces N-cyclo-hexyl-2-naphthamide (27, -45%), 2-naphthyl isocyanate (28, -50%), and a trace (<1%) of 2-naphthamide (29). 

Schrock, A. K. and Schuster, G. B., Photochemistry of naphthyl and pyrenyl azides chemical properties of the transient intermediates probed by laser spectroscopy, /. Am. Chem. Soc., 106, 5234, 1984. 

---