Visible Light-Mediated Decarboxylative Giese Addition Utilizing Thioxanthone or Thioxanthone-TfOH Complex as the Photocatalyst

Abstract

Synthetic photochemistry is an alternative, green and sustainable approach in organic synthesis, offering the possibility for the discovery of novel reactivities. Carboxylic acids are abundant and widely used as suitable radical precursors for light-mediated processes, providing access to products that are not accessible via conventional methods. Herein, we report a green, cheap, metal-free, photochemical decarboxylative protocol for the 1,4-radical conjugate addition (Giese reaction) using thioxanthone, a commercially available organic molecule, or a thioxanthone-triflic acid (TfOH) complex, as the photocatalyst, under LED 427 nm irradiation. A wide range of carboxylic acids, amino acids and Michael acceptors has been tested, affording the desired products in good to high yields.