Table 1.

Reaction condition optimization^a

Entry	Cooper catalyst	Ligand	Base	4a
				Yield/%	ee/%
1b	Cu(OTf)2	L1	K2CO3	/	/
2b	Cu(MeCN)4PF6	L1	K2CO3	66	90
3	Cu(MeCN)4PF6	L1	K2CO3	91	88
4c	Cu(MeCN)4PF6	L1	K2CO3	90	82
5	Cu(MeCN)4PF6	L1	Na2CO3	71	90
6	Cu(MeCN)4PF6	L1	K3PO4	94	86
7	Cu(MeCN)4PF6	L2	K2CO3	91	88
8	Cu(MeCN)4PF6	L3	K2CO3	72	84
9	Cu(MeCN)4PF6	L4	K2CO3	13	81
10	Cu(MeCN)4PF6	L5	K2CO3	85	82
11	Cu(MeCN)4PF6	L6	K2CO3	89	68
12	Cu(MeCN)4PF6	L7	K2CO3	36	84
13	Cu(MeCN)4PF6	L8	K2CO3	37	18
14	Cu(MeCN)4PF6	L9	K2CO3	85	16
15	Cu(MeCN)4PF6	L10	K2CO3	6	7
16 d	Cu(MeCN)4PF6	L1	K2CO3	90	90
17e	Cu(MeCN)4PF6	L1	K2CO3	97	44

Bold numbers correspond to ligand designations.

^aConditions: 1a (0.1 mmol), 2a (0.12 mmol), 3a (0.12 mmol), [Cu] (0.010 mmol), ligand (0.02 mmol), 4 Å molecular sieves (80 mg), base (3.0 equiv) in CH₂Cl₂ (4 mL), and stirred at 25°C for 36 h. Isolated yields are reported, and ee values were determined by chiral stationary HPLC.

^b2 mL of CH₂Cl₂ was used.

^c2a (0.20 mmol), 3a (0.20 mmol) were used.

^dK₂CO₃ was flame dried under vacuum in a Schlenk tube.

^eWithout 4 Å molecular sieves in CH₂Cl₂ (4 mL) and stirred at 25 °C for 3 h.