Optimization of catalyst loading for the synthesis of 2,4,5-triarylimidazole.

Entry	Catalysta (mol%)	Yieldb (%)
1	0	12
2	0.5	24
3	1.0	42
4	1.5	70
5	2.0	92
6	2.5	85
7	3.0	80

^aThe reaction was performed with benzil 1 (1 mmol), 2-nitrobenzaldehyde 2 (1 mmol), and NH₄OAc 3 in the presence of different copper(ii) salts in ethanol at 80 °C for 2 h.

^bIsolated yield.