New, Simple, and Effective Thiosemicarbazide Ligand for Copper(II)-Catalyzed N-Arylation of Imidazoles

Abstract

A new methodology of copper-catalyzed coupling reaction has been developed, involving imidazoles react with aryl halides using CuCl₂ · H₂O as catalyst and 1-(4-hydroxy-3-me thoxybenzylidene)thiosemicarbazide (L1) as ligand. It is the first time that the complex of new ligand L1 and copper(II) presents better catalytic effects than with copper(I). Because of the stability and economy of copper(II), this methodology will be a promising approach in preparing N-arylimidazoles.

GRAPHICAL ABSTRACT

Keywords:

• Aryl halide
• copper(II)
• coupling reaction
• L1
• N-arylation of imidazole

Notes

^a Unless otherwise indicated, the reaction conditions were as follows: 3-iodo-1-nitrobenzen (2.4 mmol), imidazole (2 mmol), copper salt (0.2 mmol), ligand (0.4 mol), base (4 mmol), DMF (3 mL), 110 °C, 24 h. CuI and CuBr were proceeded under N₂ protection.

^b Isolated yield based on imidazole.

^a Isolated yield based on imidazole or benzimidazole.