Multicomponent Reactions, Solvent-Free Synthesis of 2-Amino-4-aryl-6-substituted Pyridine-3,5-dicarbonitrile Derivatives, and Corrosion Inhibitors Evaluation

Table 1

Optimization of reaction conditions.

Entry	Catalyst		Aldehyde	Malononitrile	Amine	Yield (%)
1	ZnO	1.5	1	2	1	—
2	ZnO	1.5	1	2	2	—
3	ZnO	1.5	1	2	3	—
4	CAN	1.5	1	2	1	—
5	CAN	1.5	1	2	2	—
6	CAN	1.5	1	2	3	—
7	NaOEt	1.5	1	2	1	—
8	NaOEt	1.5	1	2	2	—
9	NaOEt	1.5	1	2	3	—
10	H3PO4	1.5	1	2	3	—
11	H3PO4	1.5	1	2	3	—
12	H3PO4	1.5	1	2	3	—
13	AlCl3	1.5	1	2	1	—
14	AlCl3	1.5	1	2	2	—
15	AlCl3	1.5	1	2	3	25
16	ZnCl2	1.5	1	2	1	—
17	ZnCl2	1.5	1	2	2	—
18	ZnCl2	1.5	1	2	3	45
19	FeCl3	1.5	1	2	1	—
20	FeCl3	1.5	1	2	2	—
21	FeCl3	1.5	1	2	3	37
22	Neat reaction	0	1	2	1	90

CAN = ceric ammonium nitrate.