Table 1.

Optimization Studies^a

entry	variation from standard conditions	Yield (%)	Dr (anti/syn)
1	none	99	91:9
2	0.25 mol % [Ir(dtbbpy)(ppy)2]PF6	99	91:9
3	1-adamantanethiol	99	85:15
4	1-butanethiol	96	67:33
5	cyclohexanethiol	99	78:22
6	thioacetic acid	97	2:98
7	TIPS-SH (0.5 equiv)	94	91:9
8	TIPS-SH (0.1 equiv)	99	55:45
9	MeCN as solvent	89	90:10
10	[Ir{dF(CF3)ppy}2(dtbpy)]PF6	84	21:79

^aConditions: Reaction performed at 0.1 mmol of 1a-syn with the schlenk flask submitted to 3 freeze/pump/thaw cycles prior to irradiation in the photoreactor. Yields and diastereoselectivities determined by ¹H NMR analysis of unpurified material with 1,3,5-trimethoxybenzene as an internal standard.