Photochemical transformations of 2,2'-(1,2-phenylenedivinylene)-dipyrroles

The photochemistry of 2,2'-(1,2-phenylenedivinylene)dipyrroles (4a,b) has been investigated under various conditions. After excitation of the starting material, an electron transfer followed by hydrogen transfer and radical combination occurs giving 2-[[1-(2H-pyrrol-2-ylidene)methinyl]-2-indanyl]pyrrole (14) as the intermediate. The intermediate could not be isolated, but trapped by nucleophiles, like methanol and diethylamine, giving as addition products, new functionalised indanylpyrroles (9). Irradiation of 4a in the presence of triethylamine afforded the indanylidene-pyrroles 8.