Photoinduced inverse Sonogashira coupling reaction

Area of Science:

• Organic Chemistry
• Radical Chemistry
• Synthetic Methodology

Background:

• Alkynes are versatile building blocks in chemistry, medicine, and materials science.
• Traditional Sonogashira coupling reactions often require transition metals and harsh conditions.
• Developing metal-free and milder alkynylation methods is highly desirable.

Purpose of the Study:

• To develop a novel, transition-metal and photocatalyst-free inverse Sonogashira coupling reaction.
• To utilize visible light for the direct activation of iodoalkynes.
• To explore the generation and reactivity of alkynyl radical synthetic equivalents.

Main Methods:

• Visible-light irradiation of iodoalkynes with (hetero)arenes or alkenes.
• Absence of transition metals and external photocatalysts.
• Mechanistic investigations and computational studies.

Main Results:

• Successful inverse Sonogashira coupling reaction under visible light.
• Direct activation of iodoalkynes by visible light demonstrated.
• Excited state iodoalkynes function as alkynyl radical synthetic equivalents.
• Efficient reaction with various C(sp2)-H bonds yielding coupling products.

Conclusions:

• A novel, efficient, and metal-free alkynylation strategy has been established.
• Visible light can directly activate iodoalkynes, enabling radical chemistry.
• This method offers new possibilities for alkynylation and radical reactions.