Table 1.

Knoevenagel condensation of aldehydes with ethyl cyanoacetate 2a and malonitrile 2b catalyzed by p-hydroxyapatite under solvent-free and microwave irradiation (Power = 1250 W, irradiation time = 2 min).

Entry	Product	R1	R2	Catalyst	T(°C)	Yield %	Mp (°C)[Lit.]
1	3a	C6H5	CO2Et	p-HAP300	85	46	52–54 (50) [21]
2 a	3a	C6H5	CO2Et	p-HAP300/N2	80	89
3 b	3a	C6H5	CO2Et	p-HAP300/ hydroquinone	88	88
4	3b	4-NO2C6H4	CO2Et	p-HAP300	76	96 (10)d	170–172 (172–173) [28]
5	3b	4-NO2C6H4	CO2Et	p-HAP100	62	82
6	3b	4-NO2C6H4	CO2Et	p-HAP800	50	15
7	3b	4-NO2C6H4	CO2Et	KF/Al2O3	88	80
8	3c	4-ClC6H4	CN	p-HAP300	57	93	162–164 (162) [21]
9	3d	4-CH3OC6H4	CN	p-HAP300	78	92	115–117 (116) [21]
10	3e	4-CH3C6H4	CN	p-HAP300	54	91	125–127 (129) [21]
11	3f	2-furyl	CN	p-HAP300	92	89	87–89 (91–92) [14]
12b	3g	C6H5	CN	p-HAP300/ hydroquinone	81	87
13	3h	4-NO2C6H4	CN	p-HAP300	56	96 (36)d	160–162 (161–162) [29]
14	3i	4-ClC6H4	CO2Et	p-HAP300	70	95 (28)d	92–94 (91) [21]
15	3j	4-CH3OC6H4	CO2Et	p-HAP300	64	94	86–88 (83–84) [28]
16	3k	4-CH3C6H4	CO2Et	p-HAP300	81	96	90–92 (94–95) [28]
17	3l	2-furyl	CO2Et	p-HAP300	105	90	68–70 (72) [14]
18	3m	4-(CH3)2NC6H4	CO2Et	p-HAP300	89	87	125–127 (126–127) [28]
19	3n	4-HOC6H4	CO2Et	p-HAP300	101	80	170–172 (171–172) [28]
20	3oe	propyl	CO2Et	p-HAP300	87	89	Liquid [21]
21	3pe	methyl	CO2Et	p-HAP300	87	91	Liquid [21]
22	3qe	propyl	CN	p-HAP300	89	88	Liquid [21]
23	3re	methyl	CN	p-HAP300	89	98	Liquid [21]

^a Air is excluded by purging the reaction vessel with nitrogen. ^b 20% molar of hydroquinone was added. ^c Yields of pure products obtained under MW irradiation. ^d Yields of pure products obtained under conventional heating. ^e Liquid products 3o-r were purified by chromatography on silica gel (hexane/ethyl acetate: 9/1).