Table 1. Optimization of the asymmetric Michael addition ^a .

Entry	Solvent	Cat. load (mol%)	T (°C)	t (h)	Yield b (%)	ee c (%)
1	CH2Cl2	5	rt	12	92	75
2	Toluene	5	rt	12	90	73
3	CHCl3	5	rt	12	86	61
4	Et2O	5	rt	12	88	63
5	CH2Cl2	5	0	0.5	93	89
6	Toluene	5	0	6	79	83
7	CH2Cl2	5	–20	2	93	92
8	CH2Cl2	5	–40	6	92	92
9	CH2Cl2	5	–78	6	92	92
10	CH2Cl2	7	–20	2	93	91
11	CH2Cl2	3	–20	2	93	92
12	CH2Cl2	1	–20	6	92	92

^aReaction conditions: 0.28 mmol (1.1 equiv.) of 1a, 0.25 mmol (1.0 equiv.) of 2a, 1–7 mol% of catalyst D, 0.5 mL solvent.

^bYield of isolated 3a after flash chromatography.

^cThe enantiomeric excess was determined via the O-acetylated derivative 3a′ by HPLC analysis on a chiral stationary phase.