Optimization of reaction conditions^a.

Entry	CPA	Solvent	T (°C)	Yieldb (%)	eec (%)
1	(R)-CPA1	CHCl3	RT	96	50 : 50
2	(R)-CPA2	CHCl3	RT	95	54 : 45
3	(R)-CPA3	CHCl3	RT	Trace	—
4	(R)-CPA4	CHCl3	RT	93	50 : 50
5	(R)-CPA5	CHCl3	RT	95	50 : 50
6	(R)-CPA6	CHCl3	RT	96	61 : 39
7	(R)-CPA7	CHCl3	RT	90	50 : 50
8	(R)-CPA8	CHCl3	RT	90	69 : 31
9	(R)-CPA9	CHCl3	RT	95	65 : 35
10	(R)-CPA10	CHCl3	RT	Trace	—
11	(S)-CPA11	CHCl3	RT	90	76 : 24
12	(S)-CPA12	CHCl3	RT	93	89 : 11
13	(S)-CPA13	CHCl3	RT	94	74 : 26
14	(S)-CPA14	CHCl3	RT	96	84 : 16
15	(S)-CPA12	EtOAc	RT	Trace	—
16	(S)-CPA12	THF	RT	Trace	—
17	(S)-CPA12	CH3CN	RT	92	60 : 40
18	(S)-CPA12	Acetone	RT	Trace	—
19	(S)-CPA12	Toluene	RT	95	91 : 9
20	(S)-CPA12	Toluene	10	95	92 : 8
21	(S)-CPA12	Toluene	0	93	93 : 7
22	(S)-CPA12	Toluene	−10	90	95 : 5
23	(S)-CPA12	Toluene	−40	50	95 : 5

^aAll reactions were carried out with 0.2 mmol 1a in 2 mL of solvent catalyzed by CPA (10 mol%).

^bIsolated yield of the two steps overall.

^cThe er value was determined by chiral HPLC analysis.