Table 2.

Three-component synthesis of different 2-amino-5-oxo-5,6,7,8-tetrahydro-4H-benzo[b]pyrans (4a–u) via condensation of malononitrile (1), various aldehydes (2) and dimedone (3a) or ethyl acetoacetate (3b) in the presence of CuFe₂O₄@starch at room temperature.

entry	aldehyde	product	time (min)	isolated yields (%)	m.p. (obsd) (°C)	m.p. (lit) (°C)
1	4-chlorobenzaldehyde	4a	20	96	246	240–242 [25]
2	4-nitrobenzaldehyde	4b	25	94	180–182	180–182 [11]
3	2-nitrobenzaldehyde	4c	25	91	224–226	223–225 [26]
4	3-bromobenzaldehyde	4d	30	92	211–215	224–226 [27]
5	4-hydroxybenzaldhyde	4e	30	89	121	116–120 [28]
6	4-dimethylaminobenzaldehyde	4f	35	91	225–228	220–222 [28]
7	3,4-dimethoxybenzaldehyde	4g	30	92	180–183	179–181 [29]
8	2-hydroxy 3-methoxybenzaldehyde	4h	50	87	177–180	181–183 [29]
9	3-nitrobenzaldehyde	4i	25	92	226–228	229–231 [30]
10	3-methoxybenzaldehyde	4j	35	90	193–196	195–197 [31]
11	2,4-dichlorobenzaldehyde	4k	20	94	122	120–122 [29]
12	4-methylbenzaldehyde	4l	40	93	214–216	212–214 [31]
13	4-chlorobenzaldehyde	4m	25	95	179–181	173–175 [32]
14	2-nitrobenzaldehyde	4n	32	91	185–187	183–184 [33]
15	3-nitrobenzaldehyde	4o	35	93	179–182	183–185 [32]
16	4-nitrobenzaldehyde	4p	30	96	180–183	183–185 [32]
17	4-hydroxybenzaldhyde	4q	35	89	192–194	192–194 [34]
18	4-dimethylaminobenzaldehyde	4r	45	86	160–162	163–165 [35]
19	2-chlorobenzaldehyde	4s	45	83	194–197	193–194[33]
20	3-chlorobenzaldehyde	4t	50	84	180–182	177–178 [33]
21	4-methoxybenzaldehyde	4u	40	87	138–140	140–141 [30]