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We report visible light-induced cross-dehydrocoupling of 3-cyanocoumarins with unactivated aliphatic aldehydes for the direct synthesis of 4-acylated coumarins. Inexpensive and readily available (n-Bu)4NBr was used as a precursor of the hydrogen atom transfer (HAT) catalyst and [Ir(ppy)2(dtbbpy)PF6] as a photocatalyst. A variety of aldehydes including linear, branched, cyclic, and α,β-unsaturated aliphatic aldehydes were suitable for this reaction yielding the desired acylated coumarin derivatives in 41–98% yields. This method provides a mild, atom-economical, and environmentally friendly synthetic route for the direct acylation of 3-cyanocoumarins. This is the first example so far of C-4 aliphatic acylation of coumarins.

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