Direct α-heteroarylation of amides (α to nitrogen) and ethers through a benzaldehyde-mediated photoredox reaction

A photoredox reaction for cross-dehydrogenative coupling (CDC) was developed to C-alpha-arylate amides (alpha to nitrogen) and ethers using a variety of five-and six-membered electron-deficient heteroarenes. A unique decomposition mechanism of ammonium persulfate enhanced by photoexcited benzaldehydes was revealed. This benzaldehyde-mediated photoredox reaction proceeded smoothly with household 23 W CFL bulbs as the energy source under metal-free conditions, allowing the construction of new C-sp(2)-C-sp(2) and C-sp(3)-C-sp(2) bonds and access to important pharmacophores of broad utility using commercially available reagents.