Cobalt(II) Chloride Hexahydrate as an Efficient and Inexpensive Catalyst for the Preparation of Biscoumarin Derivatives

Table 5

Comparison of the efficiency of CoCl₂·6H₂O with other reported catalysts in the synthesis of 3,3′-(3-nitrobenzylidene)-bis-(4-hydroxycoumarin).

Entry	Catalyst	Conditions	Time	Yield (%) [ref]
1	[P4VPy-BuSO3H]Cl-X(AlCl3), 0.07 mmol	Toluene, 90°C	0.5 (h)	96 [22]
2	SBPPSP, 0.06 g	EtOH/H2O, reflux	15 (min)	94 [20]
3	SDS, 20 mol%	H2O, 60°C	2.15 (h)	95 [8]
4	Nano-SiO2Cl, 75 mg	CH2Cl2, 40°C	3.5 (h)	90 [15]
5	[TBA]2[W6O19], 0.08 mmol	EtOH, reflux	7 (min)	85 [11]
6	NaHSO4·SiO2 or Indion 190 resin, 150 mg	Toluene, 100°C	30 (min)	90 [19]
7	CoCl2·6H2O, 10 mol%	EtOH/H2O, 70°C	2 (min)	98 [present work]