Visible-Light-Catalyzed Cascade Radical Cyclization for 3-Substituted Chroman-4-ones

Area of Science:

• Organic Chemistry
• Photocatalysis
• Radical Chemistry

Background:

• Chroman-4-one derivatives are important scaffolds in medicinal chemistry.
• Efficient synthesis of substituted chroman-4-ones remains a challenge.

Purpose of the Study:

• To develop a novel, efficient, and sustainable method for synthesizing 3-substituted chroman-4-one derivatives.
• To utilize visible-light photocatalysis for a cascade radical cyclization/addition reaction.

Main Methods:

• Visible-light-catalyzed, additive-free cascade radical cyclization/addition reaction.
• Photocatalytic reduction of ketoxime esters to generate nitrogen-centered radicals.
• β-C-C bond cleavage to form carbon-centered radicals.
• Intramolecular cyclization and radical addition with N-arylacrylamide.

Main Results:

• Successful synthesis of diverse 3-substituted chroman-4-one derivatives.
• The reaction proceeds efficiently at room temperature.
• The process is initiated by photocatalytic reduction of ketoxime esters.
• Nitrogen-centered radicals undergo cascade transformations to form the desired products.

Conclusions:

• A novel and efficient visible-light-catalyzed cascade reaction for chroman-4-one synthesis has been established.
• This method offers a sustainable and additive-free approach to valuable organic compounds.
• The reaction pathway involves radical intermediates and efficient cyclization/addition steps.