Screening of the reaction conditions^a.

Entry	Ligand	Solvent	Temp (°C)	Yieldb (%)	eec (%)
1	L1	MeCN	23	10	ND
2	L2	MeCN	23	72	30
3	L2	MeCN	5	61	70
4	L2	MeCN	−20	62	89
5	L3	MeCN	5	49	52
6	L4	MeCN	5	43	−44
7	L2	EtOH	5	73	74
8	L2	EtOH	−20	Trace	ND
9	L2	EtOH : MeCN (1 : 1)	−20	68	66
10	L2	EtOH : DME (1 : 1)	−20	77	76
11	L2	EtOH : DME (3 : 1)	−20	49	85
12	L2	EtOH : DME (1 : 3)	−20	83(80) d	89
13	L2	EtOH : DME (1 : 3)	−30	67	89
14e	L2	EtOH : DME (1 : 3)	−20	Trace	ND
15f	L2	EtOH : DME (1 : 3)	−20	Trace	ND
16g	L2	EtOH : DME (1 : 3)	−20	Trace	ND

^a 1a: 0.1 mmol, 2a: 0.25 mmol, blue light (λ_max 448/455 nm).

^bDetermined by ¹H NMR analysis of the crude reaction mixture with 1,1,2,2-tetrachloroethane as an internal standard.

^cDetermined by chiral stationary phase HPLC analysis.

^dIsolated yield.

^eWithout a photocatalyst.

^fReaction in the dark.

^gWithout a Cu(i) catalyst.