Easy Access to Coumarin Derivatives Using Alumina Sulfuric Acid as an Efficient and Reusable Catalyst under Solvent-Free Conditions

Table 4

Preparation of different coumarins catalyzed by ASA (0.02 g) in solvent-free conditions at 100°C.

Entry	R^1	R^2	Phenol	Time (min)	Product	Yield (%)	M.P. (°C)
							Found	Reported
1	Me	Et		30		98	187-188	182–190 [32]
2	Me	Et		75		85	239-240	240 [32]
3	Me	Et		35		89	165	165 [32]
4	Me	Et		180		25	183-184	183–185 [1]
5	Me	Et		180		N.R	—
6	Me	Et		180		N.R	—
7	Me	Et		110		60	79-80	79–81 [33]
8	Me	Et		60		91	154–156	153–155 [33]
9	Me	Et		90		85	180–182	180-181 [32]
10	Me	Et		20		55	261–263 [22]	263–265
11	Me	Me		25		99	185-186	185–190 [22]
12	Me	Me		30		80	261–263	263–265 [22]
13	CH2Cl	Et		100		96	180	180-181 [22]
14	CH2Cl	Et		35		97	283–285	284-285 [22]
15	CH2Cl	Et		500		88	165-166	165–167 [22]
17	Ph	Et		140		91	256	256 [22]

aIsolated yield.