Ionic liquids/[bmim][N3] mixtures: promising media for the synthesis of aryl azides by SNAr

The nucleophilic aromatic substitution of some activated aryl or heteroaryl halides has been performed in ionic liquid solution, using the 1-butyl-3-methylimidazolium azide as a nucleophile. The reaction course was studied varying the structures of both substrates and ionic liquids. In particular, in the latter case, the reaction of 2-bromo-5-nitrothiophene was carried out in five different ionic liquids ([bmim][BF4], [bmim][PF6], [bmim][NTf2], [bm2im][NTf2], and [bmpyrr][NTf2]). Finally, for all the substrates considered, a comparison with data obtained in MeOH solution in the presence of NaN3 was also performed. Data collected indicate that in some cases it is possible to obtain aromatic or heteroaromatic azide derivatives in satisfactory yield by means of a SNAr reaction using [bmim][N3] as the nucleophile.