Formation of Polycyclic Skeletons by Photochemical Transformations of Pyridyl- and Thienylbutadiene Derivatives

In order to study the influence of heterocyclic nuclei on the photochemical behavior of the conjugated butadiene systems, novel butadiene derivatives E,Z- and E,E-2/3-[4-(2-vinylphenyl)buta-1,3-dienyl]thiophene as well as E,Z- and E,E-3/4-[4-(2-vinylphenyl)buta-1,3-dienyl]pyridine have been synthesized. The Wittig reaction was utilized in a two-step reaction course. During the first Wittig reaction the corresponding aldehydes, namely 2/3-thiophenecarboxaldehyde and 3/4-pyridinecarboxaldehyde, reacted with formylmethylene-triphenylphosphorane to give the corresponding acrylaldehydes which reacted with diphosphonium salt of b,b'-o-xylenedibromide in the second Wittig reaction to give new butadiene derivatives. These butadiene derivatives afforded, by photochemical intramolecular cycloaddition, new fused tricyclic as well as tetracyclic derivatives. For the first time a study of efficiency was conducted where the efficiency of intramolecular cycloaddition of these heterocyclic butadiene derivatives was investigated by simultaneous use of ferrioxalate and valerophenone actinometers.