A convenient synthesis of otherwise inaccessible 3-aminocinnoline-4-carboxylic acid derivatives

Abstract

3-Amino-4-(2-nitroaryl)-2H-isoxazolin-5-ones, readily available by the sodium ethoxide catalysed cyclisation of amidoximes derived from ethyl 2-cyano-2-(2-nitroaryl)acetates, ring-close in the presence of sodium hydride to afford high yields of isoxazolo[3,4-c]cinnolin-1(3H)-one 5-N-oxides; hydrazine effects the chemoselective reductive scission of the isoxazoline ring in these heterocycles allowing simple and efficient synthetic access to erstwhile unavailable 3-aminocinnoline-4-carboxylic acid 1-N-oxides.