Proficient Procedure for Preparation of Quinoline Derivatives Catalyzed by NbCl₅ in Glycerol as Green Solvent

Table 1

The effect of various solvent in the reaction of 2-amino-benzophenone (1 mmol), 1,3-cyclohexadione (1 mmol), catalyst (0.1 mmol), and solvent (2 mL).

Entry	Solvent	Yield (%)
1	Solvent-free (80°C)	35
2	Solvent-free (100°C)	58
3	n-Hexane (r.t)	15
4	CH2Cl2 (r.t)	20
5	CHCl3 (r.t)	45
6	THF (r.t)	48
7	CH3CN (r.t)	60
8	CH3CN (80°C)	76
9	1,2-Dichloroethane (r.t)	55
10	1,2-Dichloroethane (80°C)	68
11	EtOH (r.t)	52
12	EtOH (80°C)	63
13	MeOH (r.t)	82
14	Glycerol (80°C)	83
15	Glycerol (100°C)	95
16	Glycerol (110°C)	98