67194-00-7 Cyclobuta(1,2-b:4,3-b')bisbenzofuran-5a,5b-dicarboxylic acid, 2,9-dichloro-10b,10c-dihydro-, diethyl ester, (5aalpha,5balpha,10balpha,10calpha)- Diethyl (4b-alpha,4c-alpha,9a-alpha,9b-alpha)-3,6-dichlorocyclobuta(1,2-b:3,4-b')bisbenzofuran-9a,9b(4bH,4cH)-dicarboxylate cis,Syn photodimer of ethyl 5-chlorobenzofuran-2-carboxylate