Photochemical Formation of Indanylpyrrole Derivatives from 2,2′-(o-Phenylenedivinylene)dipyrrole

Photochemically induced intra- and inter-molecular reaction of 2,2′-(1,2-phenylenedivinylene)dipyrrole (4a) led to a mixture of geometric isomers of 5-{2-pyrrolyl[2-(2-pyrrolyl)-1-indanyl]methyl}-2,2′-(1,2-phenylenedivinylene)dipyrroles (8) in 40% yield. The compounds were isolated and characterized spectroscopically and by catalytic hydrogenation to 5-{2-pyrrolyl[2-(2-pyrrolyl)-1-indanyl]methyl}-2,2′-(1,2-phenylenediethylene)dipyrrole (10). Traces of 4,5-dihydro-4-(2-pyrrolyl)benzo [5,6]cycloocta[1,2-b]pyrrole (7) were isolated in addition to 8. Under the same conditions N,N′-dimethyl-2,2′-(1,2-phenylenedivinylene) dipyrrole (4b) undergoes only cis–trans-isomerization.