Pentafluorophenyl azide

Pentafluorophenylnitrene generated by the photolysis of pentafluorophenyl-azide in toluene at 25 gives pentafluoroaniline and benzyl-substituted anilines At low temperatures (-78 to -196 °C), perfluoroazobenzene also is formed [7] (equation 8)... 

Banks and co-workers found that gas-phase pyrolysis of pentafluorophenyl azide yields a diazaheptafulvalene (Scheme 16).50 The formation of the product was viewed as dimerization of the perfluoro analogue of 4b, although it is possible that it could, instead, have been formed by dimerization of the corresponding cyclic ketenimine. 

The first nickel tetrazadiene complex, Ni(C6FjNNNNC6F5XC8H,2), obtained from Ni(CgHj2)2 and pentafluorophenyl azide, reacts with... 

Studies of the photodecomposition of azido derivatives of PCB have attracted interest because of their potential use as photolabels in intracellular distribution studies.Polyfluorinated aryl azides are also of current interest as new reagents for photoaffinity labelling. The major products of photolysis of methyl 4-azidotetrafluorobenzoate in cyclohexane or diethylamine, for example, arise by insertion, a property which enhances its use in labelling. Singlet pentafluorophenyl nitrene, formed in an analogous fashion on irradiation of pentafluorophenyl azide, can be trapped by toluene as the insertion products (79) and (80). °... 

Pentafluorophenyl azide was first synthesized by Haszeldine et al. in 1962 [92]. Ten years later, Banks and Sparkes [93] began to study the chemistry of polyfiuorinated aryl nitrenes generated by thermolysis of fluorinated aryl azides. 

Some results were also reported for the pyrolysis of pentafluorophenyl azide [94]. 

In 1986 Leyva et al. [82] reported the photochemistry of pentafluorophenyl azide in toluene. 

Figure 11. The transient absorption spectrum of pentafluoro dehydroazepine produced by laser flash photolysis of pentafluorophenyl azide in CH2C12 at ambient temperature.

TABLE 8 The Distribution of Products Formed on Photolysis of Pentafluorophenyl Azide in Cyclopentane [105 ... 

A different transient is produced upon flash photolysis of pentafluorophenyl azide in the presence of dilute pyridine (Figure 16) [109]. The transient (xmax = 520 nm) observed upon LFP of pentafluorophenyl azide in dilute pyridine is very similar to the transient observed upon LFP of phenyl azide in neat pyridine (Figure 17). The transient derived from photolysis of pentafluorophenyl azide in dilute pyridine is formed in a process which is first order in pyridine concentration and is formed with bimolecular rate constant fc = 3.1 x 109 M 1 s. The transient derived from phenyl azide reacts with pyridine with k = 4.8 x 105 M -1 s. The lifetime of the intermediate which reacts to form the transient of Figure 17, in the absence of pyridine is found... 

Poe et al. [ 109] have measured the rate of formation of ketenimine ylide 20 in the presence of traps of singlet C6F5N such as dimethylsulfide. Laser flash photolysis of pentafluorophenyl azide in the presence of various amounts of dimethylsulfide (a scavenger of singlet pentafluoro phenyl nitrene), at a fixed concentration of pyridine, lowers the yield of ylide 20, but does not increase the rate of formation of the ylide. This demonstrates that dimethylsulfide reacts with a precursor of ylide 20 (singlet pentafluorophenyl nitrene) but not the immediate precursor of the ylid (perfluorodehydroazepine). This result... 

Some studies have shown that the generation of the nitrene from pentafluorophenyl azide or from 2,6-dimethylphenyl azide from irradiation in a low-temperature matrix, permits its trapping by carbon monoxide and the formation of the corresponding isocyanate. No evidence for the ring-expansion process was seen in these experiments. Other low-temperature studies in the absence of CO trap and using N-labelled phenyl azide have shown that even at 12 K there is evidence for the ring expansion to the didehydroazepine. ... 

Photolysis of 2-, 3- and 4-fluorophenylazide (39a,b,c) in aniline gives the products (40), (41) and (42) in the yields shown in Scheme 8. " With 2,6-difluoro- and 2,3,4,5,6-pentafluorophenyl azide, however, ring expansion to azepine products analogous to (42) is suppressed, and the corresponding unsymmetrical azobenzenes cf. 41) are formed in 50% and 55% yield, respectively. The azobenzenes are presumed to arise from insertion of a singlet nitrene into an N-H bond of aniline, followed by oxidation of the resulting hydrazine. 

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