O-Nitrophenylazide

In conclusion it should be noted that the reactions of 2 equiv of ketone which result in dihydrodiazepine formation are characteristic not only of 1,2-diamines. For example, described in [104] is the interaction of or o-nitrophenylazide 95 with aliphatic and aromatic ketones (acetone, for example) in the presence of Sml2 which produces dihydrobenzodiazepines at high yields (Scheme 4.31). 

The impure azide is dissolved in 110-120 ml. of 95% ethanol at 50-55° (Note 4), and 2 g. of activated carbon is added to aid in the removal of impurities. After being filtered through a steam-heated funnel, the warm solution is allowed to cool to room temperature, whereupon 14-15 g. of the product precipitates as light-yellow prisms, m.p. 53-55°. Concentration (Note 5) of the mother liquor to 30-40 ml. by evaporation at room temperature under an air stream causes the separation of an additional 7-8 g. of material, m.p. 52-54° (Note 6). The total yield of purified o-nitrophenylazide is 63-69%. 

If the o-nitroaniline is contaminated with -nitroaniline, as it is likely to be, the yield and quality of the o-nitrophenylazide are lowered. The submitters obtained yields of 72-80% from o-nitroanilinc melting at 70-71° obtained from the Eastman Kodak Company. The yields reported were obtained with o-nitroaniline melting at 72 73.5°. 

Recrystallization of o-nitrophenylazide from a smaller volume of ethanol gives a considerably higher recovery, but it may be rather difficult to avoid separation of the product as an oil. 

Benzofurazan oxide has been prepared by a thermal decomposition of o-nitrophenylazide 4-8 by oxidation of the dioxime of o-benzoquinone by dilute nitric acid or potassium ferricyanide in alkaline solution 4 and by oxidation of o-nitroaniline with sodium hypochlorite.9 The present synthesis is a modification of the methods of Noelting and Kohn 8 and of Zincke and Schwarz.4... 

The thermolysis of methylazide was studied first by Ramsperger 21a> who found it to be a homogenous first-order reaction. Studies of thermolyses of several other organic azides in various solvents and at different concentrations also show first-order kinetics 22-28). This led to the conclusion that free nitrene intermediates are involved. There are however thermal decompositions of azides where nitrene intermediates are not involved. For example ortho-substituted arylazides like o-nitrophenylazide 2, undergo formation of benzofurazan 3 by a concerted mechanism according to l.c.21b). 

Aryl azides. In one synthesis of benzofurazane oxide (3) an aqueous solution of sodium azide is added to a solution of diazotized o-nitroaniline at 0-5°. Nitrogen is evolved, and o-nitrophenylazide separates as a light cream to colorless solid. Crystallization from 95% ethanol gives material (m.p. 52-54°) satisfactory for the... 

Benzoxadiazole-l-oxide is obtained by heating o-nitrophenylazide in acetic acid or by oxidation of o-nitroaniline with sodium hypochlorite ... 

Murata, S. and Tomioka, H., Photochemistry of o-nitrophenylazide in matrices. The first direct spectroscopic observation of o-dinitrosobenzene, Chem. Lett., 57,1992. 

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