A Completely Metal-Free Protocol for Oxidative Desulfitative C-N Coupling Reaction in Non-Basic Condition

Area of Science:

• Organic Chemistry
• Sustainable Chemistry

Background:

• Metal-catalyzed C-N coupling reactions often require harsh conditions like high temperatures, inert atmospheres, and strong bases.
• Developing metal-free alternatives is crucial for sustainable chemical synthesis.

Purpose of the Study:

• To report a novel metal-free oxidative desulfitative C-N coupling reaction.
• To utilize a latent thiol functionality in rhodanine derivatives for C-N bond formation.
• To achieve efficient coupling with poorly nucleophilic aromatic amines under mild conditions.

Main Methods:

• Activation of the latent thiol group in 5-alkylidene-rhodanine using a hypervalent iodine reagent.
• Employing ethanol as an eco-friendly solvent.
• Conducting the reaction at 50°C under ambient atmosphere.

Main Results:

• Successful C-N coupling between rhodanine derivatives and various amines, including poorly nucleophilic aromatic amines.
• The reaction proceeds efficiently without metal catalysts, inert atmosphere, high temperatures, or strong bases.
• Solid sulfur is precipitated as a byproduct, avoiding the release of hazardous hydrogen sulfide (H₂S).

Conclusions:

• This protocol offers a novel, efficient, and environmentally benign method for C-N coupling.
• The reaction's mild conditions and avoidance of toxic byproducts make it highly suitable for sustainable synthesis.
• This approach provides a valuable alternative to traditional metal-catalyzed C-N coupling methods.