Cobalt(II) Chloride Hexahydrate as an Efficient and Inexpensive Catalyst for the Preparation of Biscoumarin Derivatives

Table 4

CoCl₂·6H₂O catalyzed synthesis of biscoumarin derivatives^a.

Entry	Ar	Product	Time (min)	Yield^b (%)	mp (°C)
					Reported [ref]	This work
1	C6H5	3a	2	92	229–231 [10]	230–232
2	4-FC6H4	3b	2	97	212–214 [15]	211-212
3	4-BrC6H4	3c	5	96	266–268 [15]	264–266
4	4-CNC6H4	3d	5	96	240–242 [13]	240–242
5	2-ClC6H4	3e	3	93	201–203 [10]	200–202
6	3-ClC6H4	3f	3	94	221–223 [10]	221–223
7	4-ClC6H4	3g	1	97	261–263 [10]	256–258
8	2-O2NC6H4	3h	3	94	198–200 [10]	195–197
9	3-O2NC6H4	3i	1	98	235 [19]	234–236
10	4-O2NC6H4	3j	1	98	232–234 [20]	238-239
11	4-CH3C6H4	3k	5	92	271–273 [11]	266–268
12	4-CH3OC6H4	3l	4	94	251–253 [11]	246–248
13	3-CH3OC6H4	3m	5	92	238 [21]	238–240
14	CH3CHO	—	120	—

^aReaction conditions: 4-hydroxycoumarin (2 mmol), aromatic aldehyde (1 mmol), CoCl₂·6H₂O (10 mol%), and aqueous ethanol (5 mL), at 70°C.
^bYields refer to isolated products.