New photoinduced intramolecular ring closure to a benzopentaleno–pyrrole derivative from 5,5′-dimethyl-2,2′-(o-phenylenedivinylene)dipyrrole

New photochemically induced intramolecular cycloaddition and double cycloaddition of 5,5′-dimethyl-2,2′-(o-phenylenedivinylene)dipyrrole (4b) led to the formation of 2-{[2-(5-methyl-2-pyrrolyl)indan-1-ylidene]methinyl}-5-methylpyrrole (8) and 2-methyl-9-(5-methyl-2-pyrrolyl)-3b,4,8b,9-tetrahydro-4,5-benzopentaleno[1,2-b]pyrrole (9), respectively, in a 1:1 ratio. The compounds were characterized spectroscopically. Under the same conditions 5-methyl-2-(2-vinylphenylethenyl)pyrrole (1c) undergoes only cis–trans isomerization and decomposition.