Aryne Generation from Aryl Halides Via Photothermal Red-Light Activation

Area of Science:

• Organic Chemistry
• Synthetic Methodology
• Photochemistry

Background:

• Traditional aryne generation methods often require harsh conditions and lack atom economy.
• Existing methods for mild aryne generation typically rely on activated precursors.
• The Kobayashi method is a long-standing standard for aryne generation.

Purpose of the Study:

• To develop a simplified method for generating arynes from readily available aryl or heteroaryl halides.
• To enable mild aryne generation under ambient conditions using photothermal conversion.
• To facilitate the synthesis of C-N bonds, crucial for pharmaceuticals and agrochemicals.

Main Methods:

• Photothermal conversion of aryl or heteroaryl halides using red light irradiation.
• Utilizing carbon black as a photothermal agent to create inhomogeneous thermal gradients.
• Trapping of the generated aryne intermediate with nitrogen nucleophiles.

Main Results:

• Successful generation of arynes from various aryl and heteroaryl halides in under 20 minutes.
• Demonstrated C-N bond formation via amination, with regioselectivity supporting an aryne mechanism.
• Showcased aryne trapping via [4 + 2] cycloaddition and with sulfur nucleophiles, alongside a double amination.

Conclusions:

• The photothermal method provides on-demand access to arynes from simple aryl halides without inert conditions or additional synthetic steps.
• This approach overcomes operational barriers associated with traditional aryne generation.
• The developed method offers a simplified and efficient route to C-N bond formation for synthesizing valuable organic molecules.