A Fast, Highly Efficient, and Green Protocol for Synthesis of Biscoumarins Catalyzed by Silica Sulfuric Acid Nanoparticles as a Reusable Catalyst

Table 2

SiO₂-OSO₃H NPs catalyzed the synthesis of biscoumarin derivatives.

Entry	Ar	Product	Yield^a %	m.p./°C
				Found	Reported [Ref]
1	C6H5	4a	93	228–230	229–231 [11]
2	4-BrC6H4	4b	86	266–268	265–267 [9]
3	4-FC6H4	4c	90	211–213	213–215 [9]
4	4-MeC6H4	4d	96	268–270	266–269 [11]
5	2-OHC6H4	4e	94	253–255	254–256 [11]
6	4-OHC6H4	4f	93	194–196	193 [5]
7	4-(CH3)2NC6H4	4g	92	221–223	222–224 [9]
8	3-NO2C6H4	4h	95	215–217	214-215 [11]
9	4-NO2C6H4	4i	96	233–235	233–235 [11]
10	3-ClC6H4	4j	91	222–224	221–223 [11]
11	4-ClC6H4	4k	95	262–264	261–263 [11]
12	3-Pyridyl	4l	88	279–281	278 [5]
13	3-NO2-4-ClC6H3	4m	92	249–252	—
14	2,4-ClC6H3	4n	89	198–200	—
15	4-NO2C6H4CO	5a	96	249–251	—
16	4-BrC6H4CO	5b	90	204–207	—
17	C6H5CO	5c	93	209–211	—

aIsolated yield.