Direct Synthesis of 4-Aryl-1,2,3-triazoles via I₂-Promoted Cyclization under Metal- and Azide-Free Conditions

Area of Science:

• Organic Synthesis
• Medicinal Chemistry
• Heterocyclic Chemistry

Background:

• 1,2,3-triazoles are important heterocyclic compounds with diverse applications.
• Existing synthetic routes often involve hazardous reagents like azides or expensive metal catalysts.
• Developing efficient and safe methods for triazole synthesis is crucial for drug discovery.

Purpose of the Study:

• To develop a novel, metal- and azide-free synthetic route for 4-aryl-NH-1,2,3-triazoles.
• To utilize p-toluenesulfonyl hydrazines and 1-aminopyridinium iodide as safe azide surrogates.
• To provide a practical method for synthesizing indoleamine 2,3-dioxygenase (IDO) inhibitors.

Main Methods:

• An iodine-mediated formal [2 + 2 + 1] cyclization reaction.
• Employing methyl ketones, p-toluenesulfonyl hydrazines, and 1-aminopyridinium iodide as starting materials.
• Conducting the reaction under metal- and azide-free conditions.

Main Results:

• Successful preparation of various 4-aryl-NH-1,2,3-triazoles.
• Demonstration of p-toluenesulfonyl hydrazines and 1-aminopyridinium iodide as effective azide surrogates.
• Rapid and practical access to potent indoleamine 2,3-dioxygenase (IDO) inhibitors was achieved.

Conclusions:

• A novel and efficient metal- and azide-free synthetic strategy for 4-aryl-NH-1,2,3-triazoles has been established.
• This method offers a safer alternative to traditional triazole synthesis.
• The developed approach facilitates the discovery of new therapeutic agents, particularly IDO inhibitors.