Ab. Brown et al., SCOPE AND STEREOCHEMISTRY OF [2-PHOTOCYCLOADDITIONS BETWEEN CYCLOPENTENONES AND 1,2-DICHLOROCYCLOALKENES(2]), Synthetic communications, 27(11), 1997, pp. 1989-2011
Cyclopentenone and dichlorocycloalkenes give [2+2] adducts whose stere
ochemistry (from modern NMR) is mostly cis,anti,cis; cis,syn,cis minor
adducts are also found. Cophotolysis of dichlorocyclohexene and cyclo
heptanocyclopentenone does not give any adduct.