Table 1.

Optimization of the reaction conditions ^a.

Entry	Base	Temp. (°C)	Solvent	Time (min)	Yield (%) b
1	K2CO3	MW 80	DCE	10	27 c
2	Na2CO3	MW 80	DCE	10	21
3	NaOH	MW 80	DCE	10	12
4	NaHCO3	MW 80	DCE	10	17
5	tBuOLi	MW 80	DCE	10	complex
6	DABCO	MW 80	DCE	10	19
7	DBU	MW 80	DCE	10	45
8	TEA	MW 80	DCE	10	23
9	DBU	MW 80	DMSO	10	29
10	DBU	MW 80	DMF	10	31
11	DBU	MW 80	Toluene	10	13
12	DBU	MW 80	THF	10	<10
13	DBU	MW 80	MeCN	10	57
14	DBU	MW 80	EtOH	10	trace
15	DBU	MW 80	Dioxane	10	43
16	DBU	MW 80	1-hexanol	10	32
17	DBU	MW 80	N-ethylpyrrolidone	10	40
18 c	DBU	MW 80	MeCN	10	61
19 c	DBU	MW 100	MeCN	10	72
20 c	DBU	MW 120	MeCN	10	72
21	DBU	MW 100	MeCN	5	58
22	DBU	MW 100	MeCN	15	71
23	DBU	100	MeCN	1 h	51

^a Reaction conditions: 1a (0.3 mmol), 2a (0.3 mmol), Base (1.0 equiv.), solvent (3.0 mL). ^b Isolated yield. ^c 30 mol% DBU. Most of the starting materials were left.