Table 1.

Catalyst Screening and Reaction Condition Optimizations^[a]

Entry	Cata- lyst	Additive	Solvent	Yield (%)[b]	ee (%)[c]
1	1	none	CH2Cl2	50	9
2	2	none	CH2Cl2	59	13
3	3	PhCO2H[d]	CH2Cl2	11	3
4	4	PhCO2H[d]	CH2Cl2	9	10
5	5	none	CH2Cl2	0	-
6	6	PhCO2H[e]	CH2Cl2	49	6
7	7	PhCO2H	CH2Cl2	45	17
8	8	PhCO2H	CH2Cl2	46	57 [f]
9	8	CH3CO2H	CH2Cl2	30	71[f]
10	8	EtCO2H	CH2Cl2	39	74[f]
11	8	CF3CO2H	CH2Cl2	23	41[f]
12	8	p-TsOH	CH2Cl2	0	-
13	8	MBA[g]	CH2Cl2	46	75[f]
14	8	MBA[g]	THF	51	86[f]
15	8	MBA[g]	CH3CN	38	77[f]
16	8	MBA[g]	hexane	45	84[f]
17	8	MBA[g]	benzene	53	83[f]
18	8	MBA[g]	toluene	53	91[f]
19[g]	8	MBA[g]	toluene	75	93[f]

^[a]Unless otherwise specified, all reactions were carried out with 10a (0.30 mmol) and 9a (1.5 mmol) in the specified solvent (2.0 mL) with the amine catalyst (10 mol %) and the acid cocatalyst (30 mol %) at rt for 7 days.

^[b]Yield of isolated product after column chromatography.

^[c]Determined by HPLC analysis on a ChiralCel OJ-H column.

^[d]The loading of the acid cocatalyst was 10 mol %.

^[e]The loading of the acid cocatalyst was 20 mol %.

^[f]The opposite enantiomer was obtained.

^[g]4-Methoxylbenzoic acid.

^[h]Carried out at 0 °C.