Investigation of catalytic behaviour of TMIPOP and its relative intermediates and other known catalysts upon the synthesis of 1a^a.

Entry	Catalyst	Load of catalyst	Yield (%)
1	TIPOP	20 mg	62
2	FeCl3	20 mol%	35
3	TMIPOP	20 mg	80
4	HCl	20 mol%	Trace
5	AlCl3	20 mol%	25
6	H2SO4	20 mol%	45
7	Trityl chloride	20 mol%	30
8	Trityl bromide	20 mol%	42
9	Silica sulfuric acid (SSA)63	20 mg	75
10	NH2SO3H	20 mol%	20
11	Fe(HSO4)3	20 mol%	35
12	Al(HSO4)3	20 mol%	30
13	Ca(HSO4)2	20 mol%	25

^aReaction conditions: benzaldehyde (1 mmol, 0.106 g), ke3 (1 mmol, 0.370 g), 3-(1H-indol-3-yl)-3-oxopropanenitrile (1 mmol, 0.184 g) and ammonium acetate (1.5 mmol, 0.115 g). Solvent-free, 110 °C, 45 min.