SiO₂-NHC-Cu^I–Catalyzed N-Arylation of Imidazoles with Arylboronic Acids Under Base-Free Reaction Conditions

Abstract

N-Arylation of imidazoles with arylboronic acids was efficiently carried out in the presence of a catalytic amount of SiO₂-NHC-Cu^I in methanol at room temperature under base-free reaction conditions. The reactions of a variety of arylboronic acids with imidazoles generated the corresponding products N-arylimidazoles in good to excellent yields. In addition, SiO₂-NHC-Cu^I could be recovered and recycled for six consecutive trials without significant loss of its reactivity.

GRAPHICAL ABSTRACT

Keywords:

• Arylboronic acid
• copper(I)
• heterogeneous catalyst
• imidazoles
• N-arylation
• NHC

ACKNOWLEDGMENTS

We gratefully acknowledge financial support by the National Natural Science Foundation of China (20972057) and the Natural Science Foundation of Anhui (No. 090416223).

Notes

^a SiO₂-NHC-Cu^I(containing Cu 0.05 mmol, 5 mol%), imidazole (1.1 mmol), and phenylboronic acid (1.0 mmol) was carried out in solvent (3.0 mL) at 50 °C for 3 h under air.

^b Isolated yields.

^a SiO₂-NHC-Cu^I(containing Cu 0.05 mmol, 5 mol%), azole (1.1 mmol), and arylboronic acid (1.0 mmol) was carried out in CH₃OH (3.0 mL) at 50 °C for 3 h under air.

^b Isolated yields.

^a Reused SiO₂-NHC-Cu^I (containing Cu 0.05 mmol, 5 mol%), imidazole (1.1 mmol), and phenylboronic acid (1.0 mmol) was carried out in CH₃OH (3.0 mL) at 50 °C for 3 h under air.

^b Isolated yields.