Table 1. Optimization of the Catalyst Amount, Solvent, and Temperature for the Synthesis of 4a^a.

entry	catalyst (g)	solvent	temperature (°C)	time (min)	yield (%)b	conv (%)c
1	no catalyst		r.t.	120	trace	0
2	0.005	EtOH	reflux	60	45	70
3	0.01	EtOH	reflux	30	65	81
4	0.03	EtOH	reflux	30	77	95
5	0.05	EtOH	reflux	10	96	100
6	0.07	EtOH	reflux	20	80	100
7	0.1	EtOH	reflux	20	75	100
8	0.15	EtOH	reflux	30	71	99
9	0.05	H2O	reflux	30	55	100
10	0.05	H2O:EtOH (1:1)	reflux	45	73	100
11	0.05	CH3OH	reflux	60	70	97
12	0.05	CH2Cl2	reflux	110	55	87
13	0.05	CH3CN	reflux	110	40	85
14	0.05	toluene	reflux	120	45	66
15	0.05	DMF	reflux	100	53	75
16	no catalyst	EtOH	reflux	120	10	15
17	no catalyst	EtOH	r.t.	120	trace	0

^aReaction conditions: benzaldehyde (1 mmol), phenol (1 mmol), malononitrile (1 mmol), various solvents (2 mL).

^bIsolated yield.

^cConversions were calculated from the ¹H NMR spectrum of crude products.