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Issue 6, 2019
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Tandem synthesis of 4-aminoxanthones is controlled by a water-assisted tautomerization: a general straightforward reaction

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Abstract

Aminoxanthones constitute a group of therapeutically promising compounds that so far have been synthetically challenging. Here, we report the synthesis of both aminodihydroxanthones and fully aromatized aminoxanthones by an easy to perform, one-step multicomponent reaction of isocyanides, 3-carbonylchromones and dienophiles. The mechanism of the reaction involves a sequence of a [4 + 1] cycloaddition, iminolactone-aminofuran tautomerization, [4 + 2] cycloaddition, oxygen ring opening and aromatization. Remarkably, DFT quantum chemical computations revealed that the iminolactone-aminofuran tautomerization requires the assistance of a water molecule and, contrary to intuition, it is the rate-determining step. Conversely, both the [4 + 1] and the [4 + 2] cycloadditions have relatively low calculated energy barriers, regardless the substituents on the starting materials. Thus, we have stablished a straightforward and a wide-ranging synthesis of diversely substituted xanthones. This highly convergent process has also been applied to the synthesis of biologically important chromenophenantridines and secalonic acid related xanthone dimers.

Graphical abstract: Tandem synthesis of 4-aminoxanthones is controlled by a water-assisted tautomerization: a general straightforward reaction

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Publication details

The article was received on 11 Oct 2018, accepted on 14 Jan 2019 and first published on 17 Jan 2019


Article type: Paper
DOI: 10.1039/C8OB02527D
Citation: Org. Biomol. Chem., 2019,17, 1410-1422

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    Tandem synthesis of 4-aminoxanthones is controlled by a water-assisted tautomerization: a general straightforward reaction

    A. Bornadiego, J. Díaz and C. F. Marcos, Org. Biomol. Chem., 2019, 17, 1410
    DOI: 10.1039/C8OB02527D

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