Entry

Catalyst

Conditions

Time (mins)

Yield (%)

Ref.

1

Dowex-50 W

Solvent free/100˚C

90

78

[10]

2

Molecular iodine

Solvent free/90˚C

20

90

[11]

3

Heteropolyacid

Solvent free/100˚C

30

89

[12]

4

Fe3O4@SiO2-Imid-PMAn

Solvent free/110˚C

90

95

[13]

5

Montmorillonite K-10

Solvent free/MW

04

92

[14]

6

[Et3N?SO3H]Cl

Solvent free/120˚C

30

96

[15]

7

[H-NMP][HSO4]

Solvent free/110˚C

12

94

[16]

8

SiO2?Pr?SO3H

Solvent free/125˚C

20

98

[17]

9

HBF4-SiO2

Solvent free/120˚C

90

92

[18]

10

NSPV PHS

Ultrasound irradiation

05

95

[19]

11

[BMIm][BF4]

Solvent free/80˚C

300

98

[20]

12

L-Pyrrolidine-2-carboxylic

acid sulfate(LPCAS)

Solvent free/100˚C

06

95

This work