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A direct electrooxidative cross-dehydrogenative-coupling (CDC) reaction between N-aryl-tetrahydroisoquinolines and 4-hydroxycoumarins has been realized. This protocol provides a green, mild and fast method to construct 3-tetrahydroisoquinoline substituted coumarins in the absence of any catalysts and exogenous oxidants. A variety of N-aryl-tetrahydroisoquinolines and 4-hydroxycoumarins are compatible with this transformation to give the corresponding products in moderate to excellent yields. Moreover, the results of control experiments, cyclic voltammetry experiments, and density functional theory (DFT) calculations indicated that the electrooxidative CDC reaction might involve both radical addition and nucleophilic addition processes. [ABSTRACT FROM AUTHOR]

A mild and efficient visible-light-induced synthesis of C-3 dicarbonyl coumarins from 3-arylacetylene coumarins without a photocatalyst was reported. This iodide-mediated method exhibited broad substrate scope and good functional group tolerance, and a series of C-3 dicarbonyl coumarins were obtained in moderate to excellent yields. Based on the control experimental results, it was found that the visible-light-induced oxidation might be via both radical and ionic processes. Moreover, some synthesized compounds displayed high sensitivity to hydrogen peroxide (H2O2) with a low detection limit (DL, down to 0.149 μM). [ABSTRACT FROM AUTHOR]

An efficient and mild one-pot stepwise method to synthesize 3-alkyl coumarins is reported. Various 3-alkyl coumarins were synthesized under 3 W blue LEDs irradiation at room temperature from cheap and easily available salicylaldehydes. Based on the results of control experiments and the literature, it is found that the reaction might proceed via Wittig/cyclic condensation/radical alkylation processes. [Display omitted] [ABSTRACT FROM AUTHOR]

Cu-catalyzed CDC reactions of coumarins with cyclic ethers and cycloalkanes were achieved to afford a variety of C-3 functionalized coumarins bearing the C(sp 2 )–C(sp 3 ) bond in moderate to excellent yields. The conversion was proposed to proceed via a radical process. [ABSTRACT FROM AUTHOR]

An efficient one-pot method involving visible-light-induced cyclization and Pd-catalyzed Suzuki cross-coupling processes to construct 3,4-diaryl coumarins is developed. Under the light on-off optimized conditions, a series of alkynoates and aryl boronic acids were well suitable for this catalytic system, and were successfully transformed into the corresponding products in moderate to high yields. Meanwhile, this synthetic system has good applicability for other Pd-catalyzed coupling reactions, such as Heck and Sonogashira reactions. 3,4,7-Triphenyl coumarin could be produced not only via the Suzuki reaction of 3-bromo-4,7-diphenyl with PhB(OH) 2 , but also via the Pd-catalyzed C–H activation. Based on the spectral studies, we found that some of the 3,4-diaryl coumarins may have AIE activities. This work provides a straight forward way to create valuable multi-substituted coumarins with potential AIE properties. Image 1 • The one-pot method involves photocatalysis and thermocatalytic processes. • The light "on-off" stepwise one-pot method has excellent substrate tolerance. • A straight forward way to obtain various types of multi-substituted coumarins. • Some of the synthesized 3,4-diaryl coumarins have potential AIE activities. [ABSTRACT FROM AUTHOR]

4-Methylcoumarins yield only trace amounts of product due to steric hindrance. [ABSTRACT FROM AUTHOR]