ChemInform Abstract: Synthesis of New Heterocyclocoumarins from 3,4‐Diamino‐ and 4‐Chloro‐3‐nitrocoumarins.

Abstract

The cyclocondensation reactions of 3,4‐diaminocoumarin (II), prepared by electrochemical reduction of 3‐nitro‐4‐aminocoumarin (I), with various carbonyl compounds are described.

3‐Nitrocoumarin Amidines: A New Synthetic Strategy for Substituted [1]Benzopyrano[3,4‐d]imidazol‐4(3H)‐ones

“…3,4-Diaminocoumarin (5) is a known product. [3] General Procedure for the Synthesis of Amidine Derivatives 3a؊e:…”

“…Annular tautomerism is common in heteroaromatic compounds and has been widely studied, but literature relating to the benzopyranoimidazolone nucleus pays poor attention to the tautomerism problem. [3,5] The authors of the cited references [3,5] assign two opposite tautomeric structures to the same compound and the 1 H NMR spectroscopic data for this product are not very detailed.…”

“…[14] When the reactions were carried out in aqueous methanol solution at room temperature, mixtures of two products were obtained. Chromatographic separation of the crude mixtures afforded the coumarin imidazolones 4aϪe and the known 3,4-diaminocoumarin (5) [3] as a by-product in yields varying from 15 to 20% (Scheme 2). Scheme 2 The isolation of 3,4-diaminocoumarin (5) is not surprising.…”

“…The main synthetic approach involves the condensation of 3,4-diaminocoumarin with formic [2] or acetic acid. [3] Benzopyranoimidazolones can also be obtained from 3,4-diaminocoumarin through fusion or anodic oxidation of the useful amidic [5] or iminic [6] derivatives, respectively. These methods provide coumarin-imidazole derivatives in good yields, but they are restricted to the synthesis of 1-and 2-alkyl(and/or aryl)-substituted compounds.…”

“…[1] In the recent years a range of activities have been claimed for some coumarins fused to imidazole rings. The coumarin-imidazole nucleus, for instance, is present in compounds useful as CNS depressants, [2] as growth inhibitors of mammalian cancer [3] and also as phosphodiesterase VII inhibitors for treatment of immunity-associated diseases. [4] Few synthetic ways to prepare benzopyranoimidazolone derivatives have been reported in the literature.…”