Visible Light Photoredox Catalysis with CO₂: Difunctionalization of Terminal Alkynes

Abstract

The development of carbon dioxide (CO₂) capture and utilization is of vital importance. However, previous photocatalytic reduction reactions for converting CO₂ into chemicals (e.g., CO, HCOOH, CH₄, or CH₃OH) rely heavily on sacrificial reagents. Herein, we disclose a visible light photoredox-catalyzed 1,2-difunctionalization of terminal alkynes by using CO₂ as an ideal quenching reagent and the xanthene dye Rhodamine 6G (Rh-6G) as a photocatalyst (PC) via consecutive photoinduced electron transfer (ConPET) process. The newly developed CO₂-triggered reaction provides a highly regio- and stereo-selective approach to diverse functionalized (E)-α-vinylsulfones with simultaneously efficient conversion of CO₂ into oxalate. The practicality of this protocol is demonstrated by late-stage modification of alkynes derived from biologically active natural products or drugs. Preliminary mechanistic studies suggest that the homocoupling of CO₂ radical anion results in the formation of oxalate.

Keywords

Photoredox catalysis / CO₂ conversion / ConPET / Alkynes / Difunctionalization / Radicals

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