3-Benzoyl-3,4-dihydro-2H,5H-1-benzopyrano[4,3-b]pyran-5-ones by condensation of 4-hydroxycoumarins with enone mannich bases

✍ Scribed by Ulrich Girreser; Dieter Heber; Martin Schütt

• Publisher: Journal of Heterocyclic Chemistry
• Year: 1998
• Tongue: English
• Weight: 339 KB
• Volume: 35
• Category: Article
• ISSN: 0022-152X
• DOI: 10.1002/jhet.5570350640

✦ Synopsis

Abstract

Starting from 4‐hydroxycoumarins 4 and 1‐aryl‐2‐(dimethylaminomethyl)prop‐2‐en‐1‐ones 2 the title compounds 6 have been synthesized. The reaction is initiated by addition of the C‐3 carbon atom of 4‐hydroxycoumarin to the enone double bond of the Mannich base, subsequent deamination affords the intermediate 3‐(2‐benzoylallyl)‐4‐hydroxycoumarin 8, followed by ring closure. Depending on the reaction time, varying proportions of the ketones 6 and 8 are formed and support the mechanism defined. The spectroscopic data of all products unambiguously distinguish between the coumarin and the chromone structures in favor of the former.