Table 2.

Preparation of 4H-pyrans derivatives by using Cu₂(NH₂-BDC)₂(DABCO) as the catalyst^a

.

Entry	Aldehyde	Product	Time (min)	Yield (%)b	M. P. (°C)	M.P. (°C) [Lit.]
1	4-Chloro benzaldehyde	5a	5	96	212–214	212-214 [45]
2	2-Chloro benzaldehyde	5b	6	93	209–212	211-213 [46]
3	4- Bromo benzaldehyde	5c	8	96	204–207	205-206 [43]
4	Benzaldehyde	5d	12	90	223–226	222-224 [44]
5	2-Nitro benzaldehyde	5e	9	94	215–218	213-217 [15]
6	3-Nitro benzaldehyde	5f	6	90	214–216	216-218 [47]
7	4-Nitro benzaldehyde	5g	7	92	180–184	180-182 [48]
8	4-Methyl benzaldehyde	5h	20	90	217–220	215-217 [48]
9	3-Hydroxy benzaldehyde	5i	23	88	203–206	205-206 [49]
10	4-Hydroxy benzaldehyde	5j	25	85	206–209	205-206 [50]
11	2,4-Dichloro benzaldehyde	5k	6	94	189–192	192-194 [44]
12	4-Cyano benzaldehyde	5l	8	95	220–224	221-224 [50]
13	4-Chloro benzaldehyde	6a	20	94	242–244	241-244 [50]
14	2-Chloro benzaldehyde	6b	25	90	210–212	210-212 [51]
15	4- Bromo benzaldehyde	6c	22	90	235–237	236-238 [52]
16	Benzaldehyde	6d	40	86	237–240	241-242 [53]
17	2-Nitro benzaldehyde	6e	25	85	198–200	197-199 [54]
18	3-Nitro benzaldehyde	6f	30	92	234–237	234-236 [52]
19	4-Nitro benzaldehyde	6g	20	88	223–225	222-224 [52]
20	4-Methyl benzaldehyde	6h	40	90	224–228	225-226 [44]
21	2,4-Dichloro benzaldehyde	6i	23	89	220–223	221-223 [13]
22	4- Hydroxy benzaldehyde	6j	42	86	246–248	244-246 [50]

^aReaction conditions: aldehyde (2, 1.0 mmol), malononitrile (3, 1.0 mmol), dimedone or 1,3-cyclohexandione (4a-b, 1.0 mmol), Cu₂(NH₂-BDC)₂(DABCO) (0.04 g), solvent-free and room temperature.

^bIsolated yield.