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. 2022 Jul 14;16:2275–2288. doi: 10.2147/DDDT.S364746

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© 2022 Hamid and Salih.

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Scheme 1 — Synthesis of 7-hydroxy-4-formyl coumarin (3) and 7-methoxy-4-formyl coumarin (4). Reagents and conditions: (a) 7-hydroxy-4-methyl coumarin (1), hot xylene, selenium dioxide, reflux for 12 h, 135–140 °C, filtration, yield = 22%; (b) 7-methoxy-4-methyl coumarin (2), hot xylene, selenium dioxide, reflux for 12 h, 135–140 °C, filtration, yield = 31%.