Practical, Ecofriendly, and Chemoselective Method for the Synthesis of 2-Aryl-1-arylmethyl-1H-benzimidazoles Using Amberlite IR-120 as a Reusable Heterogeneous Catalyst in Aqueous Media

Figures & data

Scheme 1 Synthesis of 2-aryl-1-arylmethyl-1H-benzimidazoles.

Table 1. Optimization of the reaction conditions ^b

Entry	Catalyst	Catalyst load (g)	Solvents	Time (h)	Yield (%) ^a
1	Amberlite IR-120	0.100	H2O	3.00	66
2	Amberlite IR-120	0.100	EtOH	1.45	90
3	Amberlite IR-120	0.100	EtOH + H2O (2:1)	1.45	95
4	Amberlite IR-120	0.050	EtOH + H2O (2:1)	7.00	80
5	Amberlite IR-120	0.075	EtOH + H2O (2:1)	3.00	86
6	Amberlite IR-120	0.125	EtOH + H2O (2:1)	2.00	95
7	Amberlite IR-120	0.150	EtOH + H2O (2:1)	2.00	95
8	Amberlite IR-120	0.100	EtOH + H2O (1:2)	2.50	83
9	Amberlite IR-120	0.100	EtOH + H2O (1:1)	2.10	90
10	Amberlite IR-120	0.100	EtOH + H2O (3:1)	1.45	92
11	Amberlite IR-120	0.100	MeOH	6.30	84
12	Amberlite IR-120	0.100	MeOH + H2O (2:1)	7.00	85
13	Amberlite IR-120	0.100	MeCN	22.00	59
14	Amberlite IR-120	0.100	CHCl3	10.00	47
15	Amberlite IR-120	0.100	CH2Cl2	10.00	37
16	Amberlite IR-120	0.100	Toluene	10.00	51
17	Amberlite IR-120	0.100	THF	9.00	62
18	Amberlite IR-120	0.100	Dioxane	9.00	53
19	Silica gel	0.100	EtOH + H2O (2:1)	3.00	80
20	Alumina	0.100	EtOH + H2O (2:1)	3.00	81

Table 2. Synthesis of 2-aryl-1-arylmethyl-1H-benzimidazole ^b

Entry	Diamines	Aldehydes	Products	Time (h)	Yield (%) ^a
1				1.45	95
2				2.30	89
3				2.55	86
4				4.0	83
5				4.3	84
6				5.4	92
7				4.4	79
8				6.5	87
9				6.4	88
10				4.0	80
11				6.3	86
12				6.4	81
13				6.5	70
14				6.0	75
15				5.4	76

Scheme 2 Synthesis of 2-(2,4-dichlorophenyl)-1H-benzimidazole.