Photoinduced Radical Reactions Research Articles

Photoinduced radical reactions of α-alkylated ethyl 2-oxo-1-cyclopentanecarboxylate derivatives: α-cleavage and cyclization to the skeleton of linear cyclohexano diquinanes

The tricyclic core of linear cyclohexano diquinanes was synthesized using photoinduced electron transfer (PET) as a key step. The reaction proceeded in high regioselective manner via ketyl radical anions leading to distonic δ-keto radical anion as reactive intermediates. The irradiation was carried out at a wavelength of 254 nm with triethylamine (TEA) as a strong reducing reagent in acetonitrile. We also showed that the photolysis of the α-alkylated 2-oxocyclopentanecarboxylate derivatives does not lead to any cyclization products via a δ-hydrogen abstraction process. In this case α-C–C bond cleavage as a predominant process was observed.

Photo-Induced Intermolecular Radical β-Addition to Chiral α-(Arylsulfinyl) Enones

Abstract The reactions of α-(arylsulfinyl) enones with alkyl radicals having a hydroxy or acetal group were examined under photo-irradiation in the presence of benzophenone. High diastereoselectivity was observed in the photo-induced radical reaction of 2-(arylsulfinyl)-2-cyclopentenones having a bulky aryl group, such as the 2,4,6-triisopropylphenyl or 2,4,6-trimethylphenyl group. The photo-induced reaction of 3-[(2,4,6-triisopropylphenyl)sulfinyl]-3-pentene-2-one in 1,3-dioxolane also gave a single diastereomer of the 1,3-dioxolan-2-yl adduct.

Modulated degradation of hydrogels with thermo-responsive network in relation to their swelling behavior

Hydrogels consisting of poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide-co-butyl methacrylate) and a novel biodegradable cross-linker were synthesized with different concentrations of ammonium peroxodisulfate (APS) as a free radical initiator by photo-induced radical reaction. The swelling ratio of the hydrogels decreased rapidly in proportion to temperature. In vitro enzymatic degradation of the hydrogels was examined in buffer solution containing papain at different temperatures. The enzymatic degradation of the hydrogel prepared with higher APS concentration was observed to proceed at 30°C, however, the hydrogel was not degraded above 35°C. Such an on-mloff switching degradation in response to temperature was not observed for hydrogels prepared with lower APS concentration. It is considered that modulated degradation of hydrogels with a thermo-responsive network is achieved by controlling the cross-link density and eliminating the entanglement of polymeric main chains.

CIDNP STUDY OF PHOTO-INDUCED RADICAL REACTION. EFFECT OF APPLIED MAGNETIC FIELD

Abstract The strength of the applied magnetic field was found to be an important factor in detecting the CIDNP signals in the photo-induced radical reaction. The effect of the magnetic field can be understood on the basis of the radical pair theory.