Optimization of the reaction conditions for the synthesis of biscoumarin derivatives catalyzed by P₄VPy.

Entry	Catalyst (mg)	Solvent	Temperature (°C)	Time (min)	Yield (%)
1	—	No solvent	RT	120	Nil
2	—	No solvent	100	120	Nil
3	20	CH3CN	RT	120	Nil
4	20	CH3CN	Reflux	120	Mixture of products
5	20	CH2Cl2	RT	120	Nil
6	20	CH2Cl2	Reflux	120	Mixture of products
7	20	EtOH	RT	120	30
8	20	EtOH	Reflux	120	60
9	10	H2O	RT	90	40
10	15	H2O	RT	90	50
11	20	H2O	RT	90	75
12	20	H2O	90	5	96
13	24	H2O/EtOH	90	5	96