Composite copper(I)-hydroxyapatite: a heterogeneous catalyst for the homocoupling reaction of biaryl compounds

Abstract

In this present study, a reusable Cu(I)-hydroxyapatite (HAp) catalyst was developed for the homocoupling of arylboronic acids under mild conditions. The investigation encompassed the examination of how different solvents and atmospheric conditions affect the performance of catalyst. The catalyst, was prepared by means of wet impregnation with an acetone-water (24:1) mixture purposely to load 10 wt% CuI onto HAp. XRD, FT-IR, and SEM-EDS analyses demonstrated that CuI was successfully deposited on the HAp surface without changing its crystal structure or shape. During the experiment, it is established that both the solvent and the atmosphere exhibited a significant impact on the homocoupling of p-tolylboronic acid. The most optimal results were achieved through the utilization of dry DMF in air at room temperature for a duration of 24 hours. In these conditions, 4,4'-dimethylbiphenyl was isolated in approximately 80% yield, as confirmed by GC-MS, 1H NMR, and 13C NMR. The catalyst stayed active over four cycles, although the yield fell to 53% by the fourth run. XRD analysis of the used catalyst revealed that the HAp structure remained mostly unchanged. When we tested different substrates, it was found that Cu(I)-HAp worked most effectively with para-substituted arylboronic acids that were less densely populated. Overall, Cu(I)-HAp has been identified to a potentially effective heterogeneous catalyst for the aerobic biaryl synthesis. The device is characterized by Its ease of use, its capacity for recycling, and its operationalization at room temperature.

Keywords

• organoboron
• biaryl
• catalysis
• copper
• homocoupling