Rhodium-catalyzed Annulative Coupling of Coumarin-3-Carboxylic Acids with Alkynes

Hayashi, Mikishiro; Komori, Kengo; Usuki, Yoshinosuke; Satoh, Toshifumi

doi:10.1246/cl.230082

Cited by 2 publications

(2 citation statements)

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“…On the basis of previous studies of the formation of isocoumarins, , isoquinolinium salts, , and indenone imines, as well as our mechanistic experiments, we can propose a plausible reaction pathway (Scheme ; for a more detailed mechanism, see Supporting Information). The tandem reaction begins with the formation of a Schiff base from benzaldehyde 1 and aminobenzoic acid 2 , followed by its involvement in the isocoumarin cycle with the first equivalent of alkyne 3 .…”

Section: Resultsmentioning

confidence: 76%

“…Transition-metal-catalyzed C–H activation has become one of the most efficient synthetic methods in terms of step- and atom-economy. , This methodology allows one to create a variety of heterocyclic motifs from simple starting materials in just one step. For example, one of the most efficient methods for the synthesis of isocoumarins is based on the C–H annulation of readily available benzoic acids with alkynes (Scheme a) . In 2012, Cheng with co-workers developed a versatile approach to isoquinolinium salts, starting from benzaldehydes, amines, and alkynes (Scheme b) .…”

Section: Introductionmentioning

confidence: 99%

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Tandem C–H Annulation Reaction of Benzaldehydes and Aminobenzoic Acids with Two Equivalents of Alkyne toward Isocoumarin-Conjugated Isoquinolinium Salts: A Family of Organic Luminophores

et al. 2023

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A novel rhodium-catalyzed tandem C−H annulation of commercially available benzaldehydes and aminobenzoic acids with 2 equiv of alkyne is reported for the construction of isocoumarin-conjugated isoquinolinium salts that demonstrate diverse outstanding photoactivity. Depending on the substituents in the isoquinolinium moiety, they display either highly efficient fluorescence (up to 99% of quantum yield) or strong fluorescence quenching, which is provided by the transfer of the HOMO from the isoquinolinium to the isocoumarin moiety. Importantly, the functional groups in the benzaldehyde coupling partner also strongly affect the reaction selectivity, shifting the pathway to the formation of the photoinactive isocoumarin-substituted indenone imines and indenyl amines. Selective formation of the latter can be achieved by using a reduced amount of the oxidizing additive.

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