When Light Meets Nitrogen-Centered Radicals: From Reagents to Catalysts

Area of Science:

• Organic Chemistry
• Catalysis
• Photochemistry

Background:

• Nitrogen-centered radicals (NCRs) are reactive species with underexplored synthetic potential due to challenges in their generation and awareness of their reactivity.
• Visible-light photoredox catalysis offers mild conditions for generating radical intermediates from organic functional groups, bypassing harsh reagents.
• Traditional nitrogen-radical chemistry lags behind carbon-radical chemistry, highlighting a need for innovative generation and application strategies.

Purpose of the Study:

• To develop novel visible-light-driven photoredox methods for generating NCRs under mild conditions.
• To explore the synthetic applications of these photogenerated NCRs in constructing complex molecules.
• To expand the scope of nitrogen-radical chemistry through innovative catalytic strategies.

Main Methods:

• Visible-light-driven photoredox-catalyzed oxidative deprotonation electron transfer to generate NCRs from N-H containing compounds (hydrazones, benzamides, sulfonamides).
• Radical cyclization reactions (5-exo, 6-endo) and cascade reactions utilizing generated NCRs.
• Visible-light-driven copper-catalyzed cross-coupling reactions of cyanoalkyl radicals and NCR covalent catalysis.

Main Results:

• Efficient generation of NCRs from various precursors via photoredox catalysis.
• Regioselective synthesis of nitrogen heterocycles through radical cyclizations and cascade reactions.
• Development of methods for synthesizing distally functionalized alkyl nitriles and difunctionalized alkenes.

Conclusions:

• Visible-light photoredox catalysis provides a powerful and controlled approach for generating and utilizing NCRs in organic synthesis.
• The developed methods enable access to diverse nitrogen heterocycles and functionalized molecules, addressing limitations in current synthetic strategies.
• This work expands the reactivity landscape of NCRs, paving the way for new catalytic transformations and applications in complex molecule synthesis.