. 2014 Dec 12;56(5):666–673. doi: 10.1016/j.tetlet.2014.12.012

Table 1.

Comparison for preparation methods of 3-substituted 3-hydroxyoxindoles with various reported catalysts

Entry	Catalyst	Reaction conditions	Time (h/min)	Yield (%)	Refs.
1	K₂CO₃	20 mol %, rt, in water	1 h	91	15a
2	Triton-B	7 mol %, rt, in water	15 min	94	15c
3	ZnO nano-rods	10 mol %, 80 °C, in water	1.5 h	95	15d
4	LiClO₄	10 mol %, 60 °C, in ethanol	4 h	93	15e
5	β-Cyclodextrin	100 mol %, 40 °C, in water	1 h	93	15b
6	β-CD-SO₃H	10 mol %, reflux in water	5 min	96	This work