Table 1. Summary of optimization studies.

Entry	Modification a , b , c	Time d (h)	3 e (%)	Recovered 4 e (%)
1	None	12/6	51	26
2	n-BuOH	12/2	67	9
3	n-BuOH, no Et3N	12/2	50 f	14
4	hν at 65 °C	21/0	18	0
5	hν at 65 °C, n-BuOH	8/0	36	0
6	hν at 65 °C with Et3N	24/0	24	0
7	None, gram-scale	55/6	61	24
8	n-BuOH, gram-scale	34/2	59	22

^aPhotochemistry was carried out using 24 W UV-lamps.

^bReactions performed in a 50 mL quartz flask on 0.5 mmol scale, unless otherwise noted.

^cGram-scale reactions were carried out a 100 mL quartz flask.

^dReaction times are reported as follows: time exposed to UV-light/time of conventional heating on the bench-top (see the ESI for a detailed description of reaction step).

^eIsolated yield after purification.

^fSide product 11 was formed in 10–15% yield.