Quinoline as a Photochemical Toolbox: From Substrate to Catalyst and Beyond

Area of Science:

• Organic photochemistry
• Radical chemistry
• Medicinal chemistry

Background:

• Photochemistry offers a distinct alternative to thermochemistry for generating reactive species.
• The Minisci-type reaction is crucial for C(sp2)-H functionalization of heteroarenes, important in drug discovery.
• Efficient radical generation and controlled addition to electron-deficient heteroarenes remain challenges.

Purpose of the Study:

• To explore the photochemical potential of quinoline beyond its role as a substrate.
• To develop quinoline-based systems for diverse radical transformations.
• To expand the scope and efficiency of C-H functionalization reactions.

Main Methods:

• Photochemical Minisci-type alkylation of quinolines.
• Investigating quinoline's redox behavior under direct excitation.
• Designing quinoline derivatives for direct photolysis to release radicals.
• Developing diarylquinoline-based organophotocatalysts and ligands for metallaphotoredox catalysis.

Main Results:

• Quinoline demonstrated dual capacity as a radical acceptor and a scaffold for radical generation.
• Novel quinoline derivatives were synthesized to act as photoactive reagents, releasing radicals.
• Diarylquinoline scaffolds were engineered into efficient organophotocatalysts and ligands for metal-catalyzed cross-couplings.
• A decade-long research program showcased quinoline's evolution into a versatile photochemical toolbox.

Conclusions:

• Quinoline's photochemical versatility extends far beyond its traditional applications.
• Rational molecular design can transform familiar scaffolds into powerful tools for synthetic chemistry.
• This work provides new paradigms for radical-based transformations and C-H functionalization.
• Light irradiation and molecular design unlock unforeseen opportunities in organic synthesis.