Optimization of reaction conditions^a.

Entry	Deviation from standard conditions	4ab(%)
1	None	88(82)c
2	Without light	—
3	R = Me or H	—
4	390 nm	76
5	427 nm	78
6	456 nm	65
7	MeCN	74
8	DMSO	46
9	THF	21
10	DCM	5
11	MeCN/DMSO = 2 : 1	77
12	MeCN/DCM = 9 : 1	73

^aConditions: 1a (0.12 mmol), 2a (0.10 mmol), 3a (0.18 mmol), MeCN/DMSO (9 : 1, 1.0 mL), rt, 18 h.

^bDetermined by HPLC with anthracene as the internal standard.

^cIsolated yield.