Optimization of the reaction conditions^a.

Entry	Organocatalyst	3a b (%)
1	TPA	94 (89)c
2	Thiol 1	ND
3	Thiol 2	ND
4	Quinuclidine	3
5	Benzoic acid	ND
6d	TPA	29
7	—	ND
8e	TPA	1
9f	TPA	ND
10g	TPA	ND

^aGeneral reaction conditions: 1a (0.10 mmol), 2a (0.20 mmol), Mes-Acr⁺ (0.005 mmol), TPA (0.010 mmol), and TFA (0.20 mmol) were reacted in dichloromethane (DCM; 2.0 mL) at room temperature under blue LED irradiation for 7 h.

^bYield was determined by ¹H NMR analysis of the crude mixture using 1,1,2,2-tetrachloroethane as an internal standard.

^cIsolated yield in parentheses.

^dWithout Mes-Acr⁺.

^eWithout TFA.

^fWithout photoirradiation.

^g1 equiv. TEMPO was added.