Potassium carbonate as a green catalyst for Markovnikov addition of azoles to vinyl acetate in PEG

Figures & data

short-legendScheme 1. Synthesis of Markonikov products using K2CO3 in PEG.

Table 1. Effect of solvents and catalysts on Markovnikov addition between azoles and vinyl acetate^a.

Entry	Solvent	Catalyst	Time (h)	Yield (%)^b
1	PEG 400	Catalyst-free	24	5
2	PEG 400	K2CO3	5	98
3	PEG 200	K2CO3	7	90
4	DMSO	K2CO3	15	72
5	DMF	K2CO3	10	85
6	Methanol	K2CO3	15	52
7	PEG 400	L-proline	14	20
8	PEG 400	NaOH	14	55
9	PEG 400	KOH	12	70
^aReaction conditions: 4-nitroimidazole (1.0 mmol), vinyl acetate (4.0 mmol), K2CO3 (0.3 mmol), solvent PEG 400 (3 mL); (room temperature).
^bIsolated yields.

Table 2. K₂CO₃ catalyzed Markovnikov addition of azoles with vinyl acetate^a.

Entry	Nu–H	Products	Time (h)	Yield (%)^b
1			5	(3a) 98
2			8	(3b) 96
3			6	(3c) 92
4			5	(3d) 85
5			7	(3e) 81
6			9	(3f) 78
7			30	(3g) 75
8			6	(3h) 82
9			6	(3i) 88
10			10	(3j) 80
^aReaction conditions: azoles (1.0 mmol), vinyl acetate (4.0 mmol), K2CO3 (0.3 mmol), solvent PEG 400 (3 mL); (room temperature).
^bIsolated yields.

Table 3. Recycling of PEG 400^a.

No. of cycles^a	Fresh	Run 1	Run 2	Run 3	Run 4
Yield (%)^b	98	98	97	96	93
Time (h)	5	5	5	5	5
^aReaction conditions: 4-nitroimidazole (1.0 mmol), vinyl acetate (4.0 mmol), K2CO3 (0.3 mmol), solvent PEG 400; ( room temperature).
^bIsolated yields.