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Synthesis of Coumarins and Derivatives. Part 1. Biomimetic synthesis of esculetin and halogenated derivatives

✍ Scribed by Fernanda Borges; Madalena Pinto

Publisher
John Wiley and Sons
Year
1992
Tongue
German
Weight
438 KB
Volume
75
Category
Article
ISSN
0018-019X

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✦ Synopsis

Abstract

Esculetin (1) and the novel compounds 5‐chloroesculetin (5) and 5‐bromoesculetin (6) were obtained from a light‐induced cyclization of trans‐caffeic acid (3) catalyzed by [FeNa(edta)] and/or H~2~SO~4~, HCI, or HBr (Scheme 1). The experimental conditions for trans‐cis‐isomerization of the cinnamic‐acid derivative 3 and subsequent non‐enzymatic cyclization were described. The photoperiod and the presence of air and iron‐chelate catalyst are shown to be important parameters that markedly affect yields. The reactions probably occur by a free‐radical mechanism involving a photo‐initiated one‐electron redox process (Scheme 2).

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## Abstract A short synthesis of the title compounds is reported. Most of the compounds prepared were found to be active against a number of pathogenic microorganisms __in vitro.__