Optimization of reaction conditions^a.

Entry	Base	Solvent	Time	Yieldb (%)
1	Cs2CO3	CH3CN	58 h	12
2	K2CO3	CH3CN	18 h	15
3	Na2CO3	CH3CN	18 h	12
4	NaOH	CH3CN	18 h	30
5	DABCO·6H2O	CH3CN	27 h	16
6	DBU	CH3CN	33 h	45
7	NEt3	CH3CN	3 h	32
8	TMG	CH3CN	5 min	87c
9	TMG	CHCl3	4 h	82
10	TMG	Toluene	4 h	74c
11	TMG	EtOAc	20 min	58
12d	TMG	CH3CN	5 min	95c
13e	TMG	CH3CN	5 min	80c

^aUnless otherwise noted, the reactions were conducted with 0.15 mmol 1a with 2.0 equivalents of 2a in the presence of 2.0 equivalents of base in 0.8 mL of specified solvent at 60 °C.

^bIsolated yields obtained by column chromatography.

^cIsolated yields obtained by filtration of the precipitate.

^d2.2 equivalents of 2a were used.

^e2.4 equivalents of 2a were used. DABCO = 1,4-diazabicyclo[2.2.2]octane; DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene; TMG = 1,1,3,3-tetramethylguanidine.