Table 1. Optimization of reaction conditions ^a .

Entry	Ligand	Solvent	Conv b (%)	1a	2a	S e
				ee c (%)	ee c , d (%)
1	L1	THF	64	98	60	17
2	L1	Toluene	71	99	42	11
3	L1	DME	43	63	74	12
4	L1	DCE	44	45	57	5
5	L2	THF	53	92	83	29
6	L3	THF	20	7	50	1
7	L4	THF	21	24	88	25
8	L5	THF	29	38	95	40
9	L6	THF	51	99.4	97	251
10	L7	THF	37	37	64	6
11	L8	THF	39	23	36	3
12	L9	THF	31	5	31	2

^aReaction conditions: CuCl (0.025 mmol), ligand (0.025 mmol), rac-1a (0.5 mmol), B₂Pin₂ (0.6 mmol), MeOK (0.1 mmol), solvent (1.5 mL) MeOH (1.0 mmol), 0 °C, 2 h.

^bCalculated conversion, C = ee_1a/(ee_1a + ee_2a).

^cDetermined by chiral HPLC and SFC analysis.

^dDiastereomeric ratio (dr) > 99 : 1 (determined by ¹H NMR).

^eSelectivity factor (s) = ln[(1 – C) (1 – ee_1a)]/ln[(1 – C) (1 + ee_1a)].