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

Table 1

Optimization of the catalysed model reaction for synthesis of 3,3′-(3-nitrobenzylidene)-bis-(4-hydroxycoumarin).

Entry	Catalyst	Amount of catalyst (mol%)	Time (min)	Yield (%)^a
1	CoCl2·6H2O	5	8	89
2	CoCl2·6H2O	10	2	98
3	CoCl2·6H2O	15	2	98
4	CoCl2·6H2O	20	2	98
5	CoCl2·6H2O	25	2	96

All reactions were carried out in aqueous ethanol at 70°C.
^aIsolated yields.