Table 2.

Optimization of reaction conditions

Entry	R	Cat	Solvent	Temp/°C	Time/h	Yield %a	ee %b
1	Ph	CPA3	DCM(D)	−60	12	63	73
2	Ph	CPA4	DCM	−60	12	24	62
3	Ph	CPA5	DCM	−60	12	75	74
4	Ph	CPA6	DCM	−60	12	94	74
5	Ph	CPA7	DCM	−60	12	58	73
6	Ph	CPA8	DCM	−60	12	11	12
7	Ph	CPA6	Toluene	−60	12	24	47
8	Ph	CPA6	Et2O(E)	−60	12	11	41
9	Ph	CPA6	THF	−60	12	<2	–
10	Ph	CPA6	D:E = 1:1	−60	12	42	88
11	Ph	CPA6	D:E = 7:3	−60	12	67	90
12	Ph	CPA6	D:E = 7:3	−70	48	93	91
13	Ph	CPA6	D:E = 7:3	−78	48	65	92
14c	Ph	CPA6	D:E = 7:3	−70	48	94	91

All screening reactions were carried out in a 10 mL glass vial with a PTFE-lined cap on a 0.1 mmol scale. 2.0 equiv of 2a, 10% mol catalyst, 1 mL solvent

^aYield represents isolated yield

^bDetermined by HPLC analysis

^c20 mol% catalyst