Cu-Photoredox-Catalyzed C(sp)-C(sp3) Coupling of Redox-Active Esters with Terminal Alkynes
Visible-light-induced C(sp)-C(sp3) coupling of redox-active esters with terminal alkynes has been developed. The activation of carboxylic acids as their redox-active ester derivatives was important to this decarboxylative alkynylation. The strategy established here facilitates the straightforward introduction of triple-bonded functional groups and avoids additional photocatalysts. A wide range of primary, secondary and tertiary acids can be converted into the target products, so this reaction exhibits a broad substrate scope and tolerance of functional groups. Mechanistic experiments suggested that this reaction may undergo a radical process. Under mild reaction conditions, copper acetylides-ligand as photocatalysts delivered an electron to redox-active ester derivatives, and generated alkyl radicals. The radical reacted with Cu (II) to deliver a Cu (III) complex, then reductive elimination gave the products.
- This article is part of the themed collection: Synthetic methodology in OBC