Ultrasonic-assisted synthesis of chrysin derivatives linked with 1,2,3-triazoles by 1,3-dipolar cycloaddition reaction

The 1,3-dipolar cycloaddition reaction between 7-(3-azidopropoxy)-5-hydroxyflavone and phenylacetylene was carried out to investigate the synthesis of 7-(3-(4-phenyl-1,2,3-triazol-1-yl)propoxy)- 5-hydroxyflavone in presence of ultrasound (sono-synthesis) and absence of ultrasound (conventional method) under relatively optimized solvent and catalyst conditions. The reaction rate was notably accelerated with the help of ultrasound irradiation. An experiment was especially carried out for investigating the acceleration mechanism of ultrasound on the cycloaddition. A novel series of chrysin derivatives linked with 1,2,3-triazoles were obtained by the copper(I)-catalyzed 1,3-dipolar Huisgen cycloaddition reaction using t-BuOH/H2O (1:1 v/v) as reaction solvents and CuSO4·5H2O/sodium ascorbate as the catalyst at room temperature in the presence of ultrasound irradiation. Their structures are elucidated by NMR, ESI MS, IR and Elemental analysis.

Research highlights
► Ultrasonic-assisted synthesis of chrysin derivatives linked with 1,2,3-triazoles by 1,3-dipolar cycloaddition reaction was investigated.
► The ultrasound irradiation accelerates the Huisgen-click reaction rate greatly under mild conditions and enhances the yields.
► The acceleration mechanism of ultrasound on the cycloaddition ascribes to the increased reaction temperatures and reactant contact surfaces through cavitation phenomena.