Nitre heteroarenes react with ethyl isocyanoacetate in the presence of 1, 8-diazabicyclo [5.4. 0] undecene (DBU) to give pyrroles or pyrimidine N-oxide depending on the structure of the starting nitro compounds. For example, 4-nitro-2, 1, 3-benzothiadiazole 3a reacted with ethyl isocyanoacetate to give ethyl 2, 1, 3-benzothiadiazole [3, 4-c] pyrrole-2-carboxylate 4a (33%), while a similar reaction with 5-nitro-2, 1, 3-benzothiadiazole 3b gave the ...
