engleski

Photoinitiated Domino Reactions : N-(Adamantyl)phthalimides and N-(Adamantylalkyl)phthalimides

Phthalimides 1-6 undergo photochemical reactions on direct irradiation as well as triplet sensitization, and give rise to new products. Besides formation of the primary photoproducts, the first photochemical step initiates a subsequent thermal domino reaction, or a domino sequence of a thermal and a photochemical reaction. The latter, involving two photochemical intramolecular γ -H abstractions, was observed with phthalimides 1, 3 and 6 and delivered stereospecifically the hexacyclic benzazepine products 12, 19 and 27, respectively. The lowest triplet states of 1-6 were characterized in several solvents upon direct and acetone sensitized excitation. The intermolecular electron transfer from triethylamine and DABCO was studied and the radical anions were observed. Electrochemical measurements showed that intramolecular electron transfer from the adamantyl group of 1-6 to the lowest triplet state of the phthalimides is not feasible. The formation of products can be explained by intramolecular H-abstraction from the (alkyl)adamantane to the excited phthalimide, either from the excited singlet state or a hidden upper excited triplet state.

adamantanes ; domino reactions ; photoinduced H-abstraction reaction ; phthalimides ; photophysics

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