Glycosyl Triazole Ligand for Temperature-Dependent Competitive Reactions of Cu-Catalyzed Sonogashira Coupling and Glaser Coupling
Nidhi Mishra, Sumit K. Singh, Anoop Singh, Anand K. Agrahari, Vinod K. Tiwari
Abstract
Glycosyl triazoles have been introduced as efficient ligands for the Cu-catalyzed Sonogashira reaction to overcome the challenges of sideways homocoupling reactions in Cu catalysis in this reaction. The atmospheric oxygen in a sealed tube did not affect the coupling, and no need of complete exclusion of oxygen was experienced in the presence of glycohybrid triazole ligand L3. High product yields were obtained at 130 °C for a variety of substrates including aliphatic and aromatic terminal alkynes and differently substituted aromatic halides including 9-bromo noscapine. In contrast, at room temperature, a very low loading of the L3-Cu catalytic system could produce excellent yields in Glaser coupling including homocoupling and heterocoupling of a variety of aliphatic and aromatic alkynes.