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. 2021 Jun 4;26(11):3409. doi: 10.3390/molecules26113409

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© 2021 by the authors.

Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

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Scheme 3 — Synthesis of chromeno[4,3-c]pyrazol-4(1H)ones 9. Reagents and conditions. (a) POCl₃, DMF, CHCl₃; (b) NH₂NHR, EtOH, TEA or NaOAc, 25 °C, 2 h, five outputs with 67–89% yield [18], 14 outputs with 38–69% yield [25].