Nafion-Catalyzed Photoreaction. Photoisomerization of 3-Methylene-1,2,4,5,6,6-hexamethylcyclohexa-1,3-diene

Article abstract of DOI:10.1021/jo00143a006

The heptamethylbenzenonium cation 2 was shown to be produced when a CH2Cl2 solution of 3-methylene-1,2,4,5,6,6-hexamethylcyclohexa-1,3-diene (1) is brought into contact with "anhydrous" Nafion in its acid form.Treatment of the Nafion with methanolic sodium hydroxide regenerates 1.Under the conditions used here, the number of active sites on the Nafion was found to be 0.347 mmol/g.Irradiation of the Nafion with light of wavelength greater than 380 nm caused 2 to be converted mostly to vinylcyclopentadiene 5, with minor amounts of pentamethylcyclopentadiene and hexamethylbenzene also being produced.No photoisomerization of 1 took place when it was irradiated under the same conditions in the absence of Nafion.The quantum efficiency for the conversion of 2 adsorbed onto the Nafion was found to be 0.48 +/- 0.05; the same value as is found for the isomerization of 2 in homogeneous solutions.The product 5 could be displaced from the Nafion by more 1.This permitted the reaction to be carried out in a continuous mode with the Nafion functioning as a photocatalyst for the process.