Table 3.

[2 + 2] dimerization of monosubstituted alkenes via photoinduced electron transfer^a

Entry	Substrate	Electron relay	Product	Yieldb,c
1		0.75 equiv. anthracene		83% (0%)
2		0.5 equiv. anthracene		73% (0%)
3		15 mol% diethylaniline		34% (0%)
4d		None		(99%)

^aReactions carried out in 0.4 M of sparged acetone.

^bAverage of two isolated yields of 100 mg scale.

^cParenthetical product yield in absence of electron relay.

^dReaction was carried out at 0 °C.