The effect of different catalysts in the Paal–Knorr reaction^a.

Entry	Catalyst	Isolated yield (%)
1	CuCl2	67
2	FeCl2	76
3	HfCl4	83
4	FeCl3	78
5	AlCl3	83
6	ZnCl2	77
7	Fe2O3	74
8	ZnO	70
9	Al2O3	55
10	TiO2	73
11	MgO	14
12	CuO	72
13	MOF-890	80
14	MOF-891	82
15	MOF-177	81
16	ZIF-8	83
17	HKUST-1	89
18	MIL-53(Al)	96
19	Non-catalyst	25

^aReaction condition: aniline (1.0 mmol), acetonylacetone (1.2 mmol) in the presence of the catalyst (5 mol%) under solvent-free sonication.