Oxidant-Free C(sp²)-H Functionalization/C-O Bond Formation: A Kolbe Oxidative Cyclization Process

Area of Science:

• Organic Chemistry
• Synthetic Chemistry
• Electrochemistry

Background:

• Dibenzopyranones are important heterocyclic compounds with diverse biological activities.
• Existing synthetic routes often require harsh conditions, multiple steps, or expensive reagents.

Purpose of the Study:

• To develop a novel, efficient, and environmentally friendly method for synthesizing dibenzopyranones.
• To explore the utility of anodic oxidation in constructing the dibenzopyranone scaffold.

Main Methods:

• Anodic oxidation and cyclization of 2-arylbenzoic acids.
• Electrochemical synthesis performed at room temperature.
• Purification and characterization of synthesized dibenzopyranones.

Main Results:

• Successful synthesis of various dibenzopyranones in good to excellent yields.
• The reaction proceeds without the need for external oxidants or electrolytes.
• High atom economy with only hydrogen gas as a byproduct.
• Demonstrated synthetic utility through the formal synthesis of Urolithins A, B, and C.

Conclusions:

• The developed anodic oxidation/cyclization is a highly efficient and sustainable method for dibenzopyranone synthesis.
• This method offers a greener alternative to traditional synthetic strategies.
• The approach is versatile and applicable to the synthesis of complex natural products.