Optimization of the reaction conditions^a.

Entry	Ligand	Yield of (3aa + 4aa)b (%)	3aa : 4aac	eec (%)
				3aa	4aa
1	w/o	13	1 : 99	—	0
2	L3-PiPr2	58	89 : 11	91	51
3d	L3-PiPr2	39	1 : 99	—	60
4	L2-PiPr2	59	60 : 40	58	83
5	L4-PiPr2	55	97 : 3	95	—
6	L4-PrPr2	55	98 : 2	79	—
7	L4-RaPr2	75	97 : 3	90	—
8	L5-RaPr2	74	98 : 2	95	—
9e	L5-RaPr2	94	98 : 2	95	—
10	L1	29	1 : 99	—	0
11	L2	33	1 : 99	—	−11

^aUnless otherwise noted, all reactions were carried out with 1a (0.05 mmol), 2a (1.0 equiv.), and ligand/Ni(OTf)₂ (1 : 1, 10 mol%) in CH₂Cl₂ (0.1 M) at 30 °C for 16 h under N₂.

^bIsolated yield of 3aa and 4aa.

^cDetermined by HPLC on a chiral stationary phase.

^dLigand/Ni(OTf)₂ (1 : 1.5).

^e 2a (1.2 equiv.) in CH₂Cl₂ (0.2 M) at 35 °C. Ts = p-tosyl.