Photoredox cobalt-catalyzed regio-, diastereo- and enantioselective propargylation of aldehydes via propargyl radicals

Catalytic enantioselective introduction of a propargyl group constitutes one of the most important carbon-carbon forming reactions, as it is versatile to be transformed into diverse functional groups and frequently used in the synthesis of natural products and biologically active molecules. Stereoconvergent transformations of racemic propargyl precursors to a single enantiomer of products via propargyl radicals represent a powerful strategy and provide new reactivity. However, only few Cu- or Ni-catalyzed protocols have been developed with limited reaction modes. Herein, a photoredox/cobalt-catalyzed regio-, diastereo- and enantioselective propargyl addition to aldehydes via propargyl radicals is presented, enabling construction of a broad scope of homopropargyl alcohols that are otherwise difficult to access in high efficiency and stereoselectivity from racemic propargyl carbonates. Mechanistic studies and DFT calculations provided evidence for the involvement of propargyl radicals, the origin of the stereoconvergent process and the stereochemical models. Catalytic enantioselective introduction of a propargyl group is an important carbon-carbon forming reactions but only few Cu- or Ni-catalyzed protocols with limited reaction modes are known. Here, the authors describe a photoredox/cobalt-catalyzed propargyl addition to aldehydes via propargyl radicals which enables the construction of a broad scope of homopropargyl alcohols.

Automated summary

Catalytic enantioselective introduction of a propargyl group is an important carbon-carbon forming reaction, but only a few Cu- or Ni-catalyzed protocols with limited reaction modes are known. Here, the authors describe a photoredox/cobalt-catalyzed propargyl addition to aldehydes via propargyl radicals which enables the construction of a broad scope of homopropargyl alcohols that are otherwise difficult to access. Mechanistic studies and DFT calculations provide evidence for the involvement of propargyl radicals, the origin of the stereoconvergent process, and the stereochemical models.