Zirconyl (IV) Nitrate as Efficient and Reusable Solid Lewis Acid Catalyst for the Synthesis of Benzimidazole Derivatives

Table 2

Synthesis of substituted benzimidazoles by ZrO(NO₃)₂-catalyzed reaction between aromatic aldehydes and carboxylic acids with o-phenylenediamines.

Entry	Amine	Reactant	Product	Yield; (%)	Time; (h)
1				85	3.9
2				96	2
3				98	3.2
4				97	3.1
5				94	3.5
6				78	4.3
7				86	3.5
8				94	2.3
9				95	2.5
10				78	3.5
11				92	3
12				76	4.5
13				96	3
14				97	2.5
15				95	3.5
16				80	4.5
17				82	3.8
18				96	2.7
19				78	4
20				82	4.1
21				85	3.1
22				87	4

aIsolated yield.