Hydroxyl ammonium ionic liquid-catalyzed simple and efficient synthesis of 5-arylidene-2,4-thiazolidinediones under solvent-free conditions

Figures & data

Scheme 1. 2-Hydroxy ethylammonium propionate catalyzed synthesis of 5-arylidene-2,4-thiazolidinediones.

Table 1. Effect of different reaction conditions on ionic liquids catalyzed synthesis of 5-benzylidene-2,4-thiazolidinedione.^a

Entry	Ionic liquids	Amount of ionic liquid (mol%)	Temperature (°C)	Time (min)	Yield^b (%)
1	2-HEAP	20	20	100	81
2	2-HEAP	20	30	60	83
3	2-HEAP	20	40	40	87
4	2-HEAP	20	50	10	91
5	2-HEAP	20	60	6	90
6	2-HEAP	20	70	3	93
7	2-HEAP	20	80	3	93
8	2-HEAP	10	70	3	86
9	2-HEAP	15	70	3	93
10	2-HEAP	25	70	3	94
11	2-HEAA	15	70	3	89
12	2-HEAF	15	70	3	72
13	No ionic liquid	–	70	60	0

^a Reaction condition: benzaldehyde (10 mmol), 2,4-thiazolidinedione (10 mmol), solvent-free conditions.

^b Isolated yield.

Table 2. 2-Hydroxy ethylammonium propionate-catalyzed synthesis of 5-arylidene-2,4-thiazolidinediones.^a

				M.p. (°C)
Entry	R	Time (min)	Yield^b (%)	Found	Reported
1	C6H5	3	93	240–242	241–242 (26)
2	4-CH3C6H4	3	90	230–232	225–226 (26)
3	4-CH3OC6H4	3	81	218–220	218–219 (26)
4	4-FC6H4	8	90	223–224	220–221 (18)
5	3-CH3OC6H4	7	83	192–194	187–190 (9)
6	4-N(CH3)2C6H4	6	80	283–285	281 (16)
7	3-NO2C6H4	35	85	187–188	185–190 (18)
8	4-HO-3-CH3OC6H3	25	92	195–197	194 (16)
9	4-ClC6H4	7	84	226–228	223–224 (18)
10^c	2,4-Cl2C6H3	15	94	213–215	215 (16)
11^c	4-NO2C6H4	10	78	261–263	261–263 (5)
12	2-HOC6H4	65	87	228–230	225–226 (18)
13	4-HOC6H4	8	84	309–310	310–312 (26)
14	C6H5CH = CH	9	84	219–221	218–220 (18)
15	2-Furyl	2	91	231–233	230–233 (18)

^a Reaction condition: aldehyde (10 mmol), 2,4-thiazolidinedione (10 mmol), 2-hydroxy ethylammonium propionate (1.5 mmol) at 70°C under solvent-free conditions.

^b Isolated yield.

^c Reactions were carried out at 90°C.

Table 3. Recycling of the 2-hydroxy ethylammonium propionate for the synthesis of 5-benzylidene-2,4-thiazolidinedione.^a

Run	Time (min)	Yield^b (%)
1	3	93
2	3	92
3	3	91
4	3	89
5	3	87
6	5	83

^a Reaction condition: benzaldehyde (20 mmol), 2,4-thiazolidinedione (20 mmol), 2-hydroxy ethylammonium propionate (3 mmol) at 70°C under solvent-free conditions.

^b Isolated yield.

Table 4. Comparison of ionic liquids used as catalysts for the synthesis of 5-arylidene-2,4-thiazolidinediones in condensation of benzaldehyde with 2,4-thiazolidinedione.

Entry	Ionic liquids	Conditions	Time (min)	Yield (%)	References
1	[bnmim]Cl (50 mol%)	Solvent-free, 80°C	50	95	(25)
2	C3[min]2·2[Br^−] (100 mol%)	Solvent-free, 80°C	120	89	(26)
3	2-HEAP (15 mol%)	Solvent-free, 70°C	3	93	Present work

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