A new efficient route to imidazo[4,5-c]pyrazol-5-ones

The synthesis of imidazo4,5-c]pyrazol-5-ones ( 6 ) is reported. 5-Amino-4-ethoxycarbonylaminopyra-zoles 3a-g when heated at 200° for 2 hours afford 6a-g. In a similar manner imidazo4,5-c]pyrazol-5-one ( 6a ) is readily obtained from 4-amino-5-ethoxycarbonylaminopyrazole ( 5a ).