Facile and one-pot synthesis of aryl azides via diazotization of aromatic amine using cross-linked poly(4-vinylpyridine)-supported nitrite ion and azidation by a Sandmeyer-type reaction

Aromatic azides are important intermediates with a variety of applications in organic and bioorganic chemistry. In this article an efficient, simple and effective method for one-pot synthesis of aryl azides from aromatic amines is described. In this procedure diazotization of aromatic amine occurs under mild conditions using cross-linked poly(4-vinylpyridine)-supported nitrite ion, [P-4-VP]NO2, in the presence of concentrated H2SO4 at low temperature (0-5 A degrees C). The in situ generated aryl diazonium salts, followed by azidation with sodium azide in water at room temperature to produce the corresponding aryl azides by the salient of nitrogen gas (Sandmeyer-type reaction). After optimization of the reaction conditions, a good range of available aromatic amines were also subjected to diazotization-azidation by using [P-4-VP]NO2/H2SO4/NaN3 in water. Various aromatic amines, with electron-withdrawing groups as well as electron-donating groups, were transformed into aryl azides in good yields. The aryl azide products were characterized by Fourier transform infrared, some of them were also characterized by proton nuclear magnetic resonance (H-1 NMR) spectroscopy, and physical properties were compared with the literature values of known compounds. The present method is compared with other reported methods in the literature, for preparation of aryl azides. The advantages of the present method over conventional classical methods are; mild reaction conditions, safe handling, rapid, and very simple work-up. The spent polymeric reagents can be regenerated and reused for several times without significant loss of their activity. In this paper we report the first procedure for facile and rapid diazotization-azidation using cross-linked poly(4-vinylpyridine)-supported nitrite ion.