Nickel-Catalyzed Sonogashira C(sp)-C(sp²) Coupling through Visible-Light Sensitization

Area of Science:

• Organic Chemistry
• Catalysis
• Photochemistry

Background:

• Sonogashira coupling is a vital reaction for forming carbon-carbon bonds.
• Traditional methods often require harsh conditions or expensive catalysts.
• Developing efficient, visible-light-driven catalytic systems remains a key challenge.

Purpose of the Study:

• To develop an efficient visible-light-initiated, nickel-catalyzed Sonogashira coupling reaction.
• To utilize an energy-transfer mechanism for accelerating the cross-coupling process.
• To broaden the scope of substrates for aryl alkyne synthesis.

Main Methods:

• Visible-light photoredox catalysis.
• Nickel-catalyzed Sonogashira cross-coupling.
• Energy transfer mechanism involving thioxanthen-9-one as a photosensitizer.
• Stepwise reaction pathway: oxidative addition, transmetalation, energy transfer, reductive elimination.

Main Results:

• High yields of aryl alkynes were achieved using a wide range of (hetero)aryl halides and alkynes.
• Thioxanthen-9-one significantly accelerated the reaction under visible light.
• The reaction proceeds efficiently via a nickel catalytic cycle facilitated by energy transfer.

Conclusions:

• An efficient and accelerated visible-light-driven Sonogashira coupling method has been established.
• The developed method offers a sustainable and effective route for synthesizing aryl alkynes.
• The energy-transfer mechanism provides new insights into photoredox-catalyzed cross-coupling reactions.