Optimization of the reaction conditions^a.

Entry	PC	Light source (nm)	9, drbanti : syn	9, yieldc (%)
1	—	400	nd	<5
2	NTC	400	>95 : 5	34
3	NTC	427	>95 : 5	31
4	Mes-Acr	456	>95 : 5	76
5	DCA	427	>95 : 5	94
6	Ph3Pyr+	456	>95 : 5	64
7d	DCA	427	45 : 55	76
8e	DCA	427	>95 : 5	94
9	DCA	—	nd	<5

^aReactions performed on a 0.2 mmol scale, using 1.2 equiv. of 8 in 4 mL of MeCN (see ESI).

^bThe dr was inferred by ¹H-NMR analysis of the reaction crude.

^cYield after isolation.

^d syn-7 was used.

^eReaction time: 10 minutes.