Table 2.

Comparison of preparative methods of 3,3-di(indolyl)indolin-2-ones with various reported catalysts

Entry	Catalyst	Reaction conditions	Time (h/min)	Yield (%)	Refs.
1	Ionic liquid	60 mol % of ([BMIM][BF4]LiCl), rt	1 h	93	16a
2	Bismuth(III) Triflate	2 mol %, CH3CN, rt	3 h	92	16b
3	Indium(III) acetylacetonate	10 mol %,(H2O:CH3CN 4:1), rt	2.5 h	92	16c
4	Silica sulfuric acid	0.2 g, CH2Cl2, rt	2 h	92	16d
5	Ruthenium trichloride	5 mol %, MeOH, 50 °C	2 h	75	16f
6	Ceric ammonium nitrate (CAN)	10 mol %, US, EtOH, rt	3 h	95	16g
7	I2 (Iodine)	10 mol %, CH2Cl2, rt	14 h	82	16h
8	KSF	0.1 g, reflux in EtOH	0.5 h	90	16i
9	β-CD-SO3H	10 mol %, H2O, reflux	5 min	96	This work