Azido-type-selective triazole formation by iridium-catalyzed cycloaddition with thioalkynes

Area of Science:

• Organic Chemistry
• Catalysis
• Click Chemistry

Background:

• Azide-alkyne cycloaddition is a cornerstone of click chemistry.
• Iridium catalysts offer unique reactivity for cycloaddition reactions.
• Understanding substrate scope and selectivity is crucial for synthetic efficiency.

Purpose of the Study:

• To investigate the influence of azide structure on iridium-catalyzed azide-thioalkyne cycloaddition rates.
• To explore the azido-type selectivity in these reactions.
• To demonstrate the utility of selective cycloadditions for constructing complex molecular architectures.

Main Methods:

• Iridium-catalyzed azide-thioalkyne cycloaddition reactions were performed using various azides and thioalkynes.
• Reaction kinetics were monitored to determine rate differences between benzyl and phenyl azides.
• Sequential click chemistry reactions were employed to build triazido platforms.

Main Results:

• Benzyl azide exhibited significantly higher reactivity compared to phenyl azide in the iridium-catalyzed cycloaddition.
• High azido-type selectivity was observed across different steric environments of the azides.
• The study successfully assembled triazido platforms via three sequential triazole-forming reactions.

Conclusions:

• The steric and electronic properties of the azide significantly impact the rate and selectivity of iridium-catalyzed azide-thioalkyne cycloadditions.
• This selective cycloaddition methodology provides an efficient route for synthesizing complex molecules with multiple triazole units.
• The findings open avenues for designing novel catalysts and synthetic strategies in organic chemistry.