Nickel-Catalyzed Azide–Alkyne Cycloaddition To Access 1,5-Disubstituted 1,2,3-Triazoles in Air and Water

Transition-metal-catalyzed or metal-free azide–alkyne cycloadditions are methods to access 1,4- or 1,5-disubstituted 1,2,3-triazoles. Although the copper-catalyzed cycloaddition to access 1,4-disubstituted products has been applied to biomolecular reaction systems, the azide–alkyne cycloaddition to access the complementary 1,5-regioisomers under aqueous and ambient conditions remains a challenge due to limited substrate scope or moisture-/air-sensitive catalysts. Herein, we report a method to access 1,5-disubstituted 1,2,3-triazoles using a Cp₂Ni/Xantphos catalytic system. The reaction proceeds both in water and organic solvents at room temperature. This protocol is simple and scalable with a broad substrate scope including both aliphatic and aromatic substrates. Moreover, triazoles attached with carbohydrates or amino acids are prepared via this cycloaddition.