Photoredox-Neutral Platform for Direct Decarboxylative Cyclopropanation via Acridine-Iron Dual Catalysis

Area of Science:

• Organic Chemistry
• Photocatalysis
• Catalysis

Background:

• Cyclopropane synthesis is crucial in organic chemistry.
• Existing methods often require harsh conditions or sacrificial reagents.
• Development of efficient and sustainable catalytic systems is needed.

Purpose of the Study:

• To report a photoredox-neutral approach for cyclopropane synthesis.
• To utilize in situ generated non-stabilized carbenes.
• To develop a new acridine-iron dual catalytic system.

Main Methods:

• Employing a dual catalytic system involving acridine photocatalysts and iron porphyrin complexes.
• Utilizing bench-stable carboxylic acids as precursors.
• Conducting reactions under mild photochemical conditions.
• Performing mechanistic studies including density functional theory (DFT) calculations.

Main Results:

• Achieved photoredox-neutral cyclopropane synthesis from carboxylic acids.
• Demonstrated efficient electron shuttling between carboxylic acids and iron complexes by acridine photocatalysts.
• Revealed a stepwise proton transfer followed by electron transfer mechanism for decarboxylation, challenging previous assumptions.
• Identified a key Fe(IV)-carbenoid intermediate facilitating carbene transfer.

Conclusions:

• The developed acridine-iron dual catalytic system provides a sustainable route to cyclopropanes.
• The mechanistic insights offer a deeper understanding of photoredox catalysis and carbene generation.
• This strategy avoids the need for sacrificial reductants, aligning with green chemistry principles.