Table 1.

Optimization of the reaction conditions

Entry	Additive	Equiv of Additive	3a/IS GC yield (%)a
1	none	none	23
2	CS2CO3	1	43
3	K2CO3	1	39
4	Na2CO3	1	37
5	K3PO4	1	30
6	NaOAc	1	18
7	NH4OAc	1	19
8b	Cs2CO3	1	52
9b	Cs2CO3	2	69
10b,c	Cs2CO3	2	87 (78d)
11b,c	CsF	2	63
12b,c,e	Cs2CO3	2	72
13b,c,f	Cs2CO3	2	Traces
14b,c, g	Cs2CO3	2	no reaction

Reaction conditions: 1a (0.1 mmol), 2a (0.1 mmol), base, dry and degassed DMSO (0.2 M) at room temperature under purple Kessil^® (390 nm) irradiation for 16 h.

^aCalculated against 1,3,5-trimethoxybenzene as internal standard (IS).

^b3 equiv of 2a.

^cSolvent 0.13 M for 1a.

^dIsolated yield at 0.5 mmol scale.

^eBlue Kessil^® (456 nm).

^fGreen Kessil^® (525 nm).

^gNo light.