1-Aryl-3-(2-hydroxyphenyl)-2-pyrazolin-5-ones are prepared from 4-hydroxycoumarin and arylhydrazines and then cyclised with triethyl orthoacetate to give 2-aryl-4-methyl[1]benzopyrano[4,3-c]pyrazol-3(2H)-ones.
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Froggett et al. (1997) studied this question.