S. No

Catalyst

Solvent used

Time (min)

Yield

Ref No

1

Triethylamine-bonded sulfonic acid

Solvent free

30 (reflux)

94

[7]

2

N, N’-dibromo-N, N’-1, 2-ethanediylbis (p-toluenesulfonamide)

Solvent free

120 (reflux)

92

[10]

3

ceric ammonium nitrate

Ethyl acetate

135 (ultrasonication)

87

[16]

4

3-sulfobutyl-1-(3-propyltriethoxysilane) imidazolium hydrogen sulfate on silica-coated Fe₃O₄ nanoparticles

Ethyl acetate

30 (reflux)

90

[11]