Straightforward chemoselective 4-nitration of 5-aminoisoxazoles

5-Aminoisoxazoles bearing 3-positioned electron-withdrawing group react chemoselectively with trifluoroacetyl nitrate (generated from ammonium nitrate and trifluoroacetic anhydride) to give the corresponding 4-nitro derivatives in yields up to 80%. The results were rationalized by computation studies. Several 5-amino-4-nitroisoxazole-3-carboxilic acid derivatives revealed moderate antibacterial activity.