Correction of a Reported Xanthone Synthesis: The Preparation of a Benzo[<i>c</i>]coumarin

Hurtley condensation was shown to be a perfect tool with which to assemble a diversified library of derivatives of benzo[c]coumarin. Not only do simple resorcinols and ortho‐bromobenzoic acids undergo this reaction, but also dihydroxynaphthalenes and 3‐bromothiophene‐2‐carboxylic acid, affording the desired compounds in moderate yields. In the case of naphthalenediols, intriguing regioselectivity is observed, which holds promise for its utilization in the synthesis of previously inaccessible molecules. Further transformation made it possible to obtain benzo[c]coumarin bearing amino and nitro groups at various positions, which served as entry points to prepare complex hybrids of 1,4‐benzoxazin‐2‐ones and benzo[c]coumarins. The hydroxyl group proved to be the synthetic handle, enabling the synthesis of strongly solvatochromic, soluble analogues. The effect of structural variation on photophysical properties was studied in detail for almost 30 compounds. The relationship between the structure and photophysical properties was thoroughly elucidated by comparison with simple analogues (coumarins, benzoxazinones). All of the obtained compounds exhibit moderate to large Stokes shifts (3300–12500 cm–1). The type of π‐expansion of the chromophore strongly influences the overall optical phenomena. Compounds possessing alkyl substituents on the benzo[c]coumarin core have much higher fluorescence quantum yields than their analogues bearing amino, fluorine, and other complex substituents. Interestingly, the product possessing a fused coumarin–thiophene skeleton exhibits over twofold higher fluorescence quantum yield than any of its coumarin–benzene analogues.

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Versatile Biaryls and Fused Aromatics through Oxidative Coupling of Hydroquinones with (Hetero)Arenes

Aijima,

Ueda,

Nakane

et al. 2024

ChemistrySelect

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Hydroquinones bearing an electron‐withdrawing group at the C2‐position can effectively underwent oxidative coupling with (hetero)arenes (e. g., indoles, electron‐rich benzene derivatives) in the presence of 2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone (DDQ) and FeCl3 to produce the corresponding biaryl products. In the present reactions, the DDQ‐mediated oxidation of hydroquinone derivatives produce benzoquinone intermediate, which subsequently underwent FeCl3‐catalyzed nucleophilic addition of (hetero)arenes to the α,β‐unsaturated carbonyl moiety to give the biaryl product in a one‐pot manner. Especially, the indole‐based biaryl products were further converted into tetracyclic aromatics through DDQ‐mediated oxidation followed by FeCl3‐catalyzed intramolecular cyclization. Thiophene derivatives were also applicable to give the tetracyclic aromatics. Moreover, the photophysical properties of the indole‐ and thiophene‐based tetracyclic aromatics in the solution and the solid states were investigated.

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Correction of a Reported Xanthone Synthesis: The Preparation of a Benzo[c]coumarin

Cited by 3 publications

References 11 publications

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Versatile Biaryls and Fused Aromatics through Oxidative Coupling of Hydroquinones with (Hetero)Arenes

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