Table 2.

Optimization of reaction parameters for the synthesis of Benzo[a]pyrano[2,3-c]phenazine derivatives^a.

Entry	Solvent	Catalyst (g)	Temp. (°C)	Time (min)	Yieldb (%)
1	CHCl3	0.015	Reflux	200	80
2	CH3CN	0.015	Reflux	50	90
3	H2O	0.015	Reflux	120	78
4	EtOH	0.015	Reflux	40	94
5	EtOH/H2Oc	0.015	90	30	96
6	EtOH/H2O	–	90	30	–
7	EtOH/H2O	0.005	90	30	32
8	EtOH/H2O	0.01	90	30	71
9	EtOH/H2O	0.02	90	30	96
10	EtOH/H2O	0.015	r.t	30	15
11	EtOH/H2O	0.015	50	30	45
12	EtOH/H2O	0.015	80	30	88

^a Reaction conditions: Thiobarbituric acid (1 mmol), o-phenylenediamine (1 mmol), 4-nitrobenzaldehyde (1 mmol), 2-hydroxy-1,4-naphthoquinone (1 mmol), solvent (3 mL), under thermal condition.

^b Product yield obtained after purification.

^c volume ratio: (1:1).