Microwave-assisted synthesis of substituted fluorophenyl mono- and diazides by SNAr. A fast methodology to prepare photoaffinity labeling and crosslinking reagents

The reaction of sodium azide with perfluorobenzene, containing an electron-withdrawing group, under microwave irradiation results in the fast preparation of p-substituted tetrafluorophenyl monoazides. Having an excess of sodium azide and a strong electron-withdrawing group like NO2 or CN, fluorophenyl diazides are also produced upon conventional or microwave heating. A synergic effect between the amount of sodium azide and the electron-withdrawing character of the substituents is observed giving different products. A discussion on the products and reaction mechanism is presented.