10.1016/S0040-4039(00)00097-6
The study focuses on the photocyclization and photooxidation processes of 3-styrylthiophene, a compound with two isomers: trans-3-styrylthiophene (1) and cis-3-styrylthiophene (2). The research investigates how these isomers react under different photochemical conditions, including in nonpolar and polar solvents, with and without sensitizers. The key findings include that cis-3-styrylthiophene (2) undergoes photochemical cis–trans isomerization and cyclization to form dihydronaphtho-[1,2-b]thiophene (3), with a higher quantum efficiency in nonpolar solvents. Dye-sensitized photooxidation of 3-styrylthiophene results in the production of benzaldehyde and 3-thiophenecarboxaldehyde, and the process is suggested to occur via a superoxide radical anion pathway rather than through singlet oxygen. Additionally, auto-photooxidation in the presence of oxygen leads to photocyclization, oxidation, and dimerization products. The study proposes that these reactions may involve the formation of a charge transfer complex between oxygen and the substrate. The research is significant for understanding the behavior of polythiophenes, which are important for the production of conductive polymers, and could contribute to improving the photostability of these materials.
10.1021/ja00234a014
The study investigates the photoinduced electron transfer reactions of trans-anethole (t-A) and cis-anethole (c-A), focusing on their isomerization, dimerization, and oxygenation processes. When irradiated in the presence of electron acceptors like 9-cyanoanthracene (CA) or 9,10-dicyanoanthracene (DCA), both t-A and c-A undergo trans,cis isomerization and dimerization to form various cyclobutane dimers, with the dimer ratio being sensitive to reaction conditions. The presence of oxygen quenches isomerization and dimerization, leading to the formation of oxygenated products like p-anisaldehyde. The study concludes that isomerization occurs via reverse electron transfer to generate triplet anethole, while dimerization proceeds via quasi-concerted [2 + 1] cycloaddition of cation radicals. The results also suggest that an acyclic 1,4-cation radical is not involved in these reactions, as no [2 + 4] dimers or 1,2-dioxanes are detected.