Table 2. Optimization of the Michael Adduct Formation between Chalcone (13a) and Lactone 2a.

entry	NBu4Br (equiv)	base (equiv)	molarity [2a]	time (h)	yield (%)a
1		K2CO3 (1.0)	0.337	24	-b
2	0.20	K2CO3 (1.0)	0.337	2	90
3	0.05	K2CO3 (1.0)	0.337	2	88
4	0.05	K2CO3 (0.10)	0.337	2.5	86
5	0.01	K2CO3 (0.01)	0.675	48	88
6	0.10	K2CO3(0.10)	0.675	5	97
7	0.10	Li2CO3 (0.10)	0.675	36	80

^aIsolated yield.

^bStarting materials recovered.