Table 1.

Optimization and control studies for photocatalytic [2+2] cycloaddition

entry[a]	catalyst	solvent	conc. (M)	yield[b]
1	2•PF6	CHCl3	0.05 M	22%
2	2•PF6	CH2Cl2	0.05 M	26%
3	2•PF6	THF	0.05 M	21%
4	2•PF6	acetone	0.05 M	24%
5	2•PF6	MeOH	0.05 M	21%
6	2•PF6	MeCN	0.05 M	13%
7	2•PF6	DMSO	0.05 M	33%
8	2•PF6	DMSO	0.01 M	89% (83%)[c]
9	1a•(PF6)2	DMSO	0.01 M	0%
10	1b•(PF6)2	DMSO	0.01 M	0%
11	none	DMSO	0.01 M	0%
12[d]	2•PF6	DMSO	0.01 M	0%

^[a]Reactions irradiated using a 23 W compact fluorescent light bulb.

^[b]Yields determined by ¹H NMR analysis against a calibrated internal standard unless noted.

^[c]Isolated yield in parenthesis.

^[d]Control reaction conducted in the dark.