Table 1.

Key reaction-controlling parameters.

Entry	Variations from standard condition	Yielda (%)
1	CySH instead of 1-AdSH	75
2	1-AdSH (10 mol %)	72
3	PO1 (2 mol %)	52
4	2 (0.4 mmol)	96
5	Et3SiH instead of HCO2K	30
6	440 nm instead of 427 nm	70
7	456 nm instead of 427 nm	trace
8	467 nm instead of 427 nm	trace
9	PPh3 instead of PO1	trace
10	4-t-Bu-C6H4OH instead of PO1	0
11	4-t-Bu-C6H4OH+PPh3 (1:1, 10 mol %)	10
12	w/o PO1	0
13	w/o 1-AdSH	trace
14	w/o HCO2K	18
15	w/o light	0
16	under air	trace

w/o without.

^aYields measured by ¹H-NMR using diphenylmethane as an internal standard.