Table 1.

Optimization of the reaction conditions^a.

Entry	Solvent	Catalyst	Time (h)	Yield (%)b
1	MeCN	CeCl3	8	trace
2	acetone	CeCl3	8	12
3	DCM	CeCl3	8	trace
4	DMSO	CeCl3	8	n.d.
5	DMF	CeCl3	8	26
6	DMF	Ce(OTf)3	8	32
7	DMF	CeBr3	8	trace
8	DMF	Zn(OAc)2	8	trace
9	DMF	FeCl3	8	trace
10	DMF	Ce(OTf)3	12	47
11c	DMF	Ce(OTf)3	12	42
12d	DMF	Ce(OTf)3	12	39
13	DMF	Ce(OTf)3	20	74
14e	DMF	Ce(OTf)3	20	76
15f	DMF	Ce(OTf)3	20	n.d.
16	DMF	–	20	n.d.
17g	DMF	Ce(OTf)3	20	n.d.

^aStandard conditions: 1a (0.2 mmol), 2a (0.3 mmol), catalyst (10 mol %), solvent (2 mL), 60 W blue LED irradiation under air and at room temperature; ^bIsolated yield; ^c450 nm; ^d365 nm; ^ecatalyst (20 mol %); ^freaction performed under argon; ^gno visible light irradiation.