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

Table 2

Optimisation of temperature for synthesis of 3,3′-(3-nitrobenzylidene)-bis-(4-hydroxycoumarin) using CoCl₂·6H₂O (10 mol%) as catalyst in aqueous ethanol.

Entry	Catalyst	Temperature °C	Time (min)	Yields (%)
1	CoCl2·6H2O	Room temperature	4	85
2	CoCl2·6H2O	Reflux	2	98
3	CoCl2·6H2O	70	2	98
4	CoCl2·6H2O	50	4	95

Isolated yield of the pure compound.