Scheme 5.
Synthesis of chromeno[4,3-c]pyrazol-4(2H)-ones 16. Reagents and conditions. (a) POCl3, DMF, CHCl3, 4 outputs with 65–80% yield; (b) NaN3, DMF, 4 outputs with 50–80% yield; (c) R1NHNH2, DMF, 40–50 °C, six outputs with 70–90% yield.
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