Synthesis and analgesic activity of 4-amino-1,2-dihydro-5-(2-hydroxyphenyl)-3H-pyrazol-3-ones and 5-amino-6-(2-hydroxyphenyl)pyrimidin-4(3H)-ones

Abstract 4-Amino-1,2-dihydro-5-(2-hydroxyphenyl)-3 H -pyrazol-3-ones 2a–c and 5-amino-6-(2-hydroxyphenyl)pyrimidin-4(3 H )-ones 3a–f were synthesized from 4-methoxy- and 4-hydroxy-3-nitrocoumarins, and tested for analgesic activity upon oral administration to mice. Most of the compounds prepared exhibited analgesic activity which was superior to that of aminopyrine. In particular, 2a–c and 3a, d showed prominent activity which was 3–4.5 times as potent as that of aminopyrine.