Electrosynthesis of Highly Functionalized Quinolines through Radical Annulation-Polar Addition Cascade

Area of Science:

• Organic Chemistry
• Electrochemistry
• Synthetic Methodology

Background:

• Quinoline-2-carboxylates are important heterocyclic compounds with diverse applications.
• Efficient and mild synthetic routes are crucial for accessing functionalized quinoline derivatives.
• Electrochemical methods offer sustainable alternatives for C-C and C-N bond formation.

Purpose of the Study:

• To develop a novel electrochemical cross-dehydrogenative coupling reaction for quinoline-2-carboxylate synthesis.
• To explore the compatibility of various functional groups under the developed reaction conditions.
• To elucidate the reaction mechanism for fabricating C-C and C-N bonds.

Main Methods:

• Electrochemical cross-dehydrogenative coupling between N-aryl glycinates and methylenecyclopropanes.
• Transition-metal- and oxidant-free reaction conditions.
• Cyclic voltammetric measurements and control experiments for mechanistic studies.

Main Results:

• Successful synthesis of diversely functionalized quinoline-2-carboxylates.
• Demonstrated broad substrate scope with excellent functional group tolerance.
• Proposed a reaction mechanism involving radical intermediates and nucleophilic polar addition.

Conclusions:

• The developed electrochemical method provides a practical and efficient route to functionalized quinoline-2-carboxylates.
• The transition-metal- and oxidant-free conditions highlight the advantages of electrochemistry in sustainable synthesis.
• The study offers valuable insights into the formation of C-C and C-N bonds through a formal [4 + 2] cycloaddition pathway.