Photoinitiated domino reactions: N-(adamantyl)phthalimides and N-(adamantylalkyl)phthalimides.
Phthalimides 1-6 undergo photochemical reactions upon 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 gamma-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.
Horvat
Margareta
M
Department of Organic Chemistry and Biochemistry, Ruder Bosković Institute, Bijenicka cesta 54, 10 000 Zagreb, Croatia.
Görner
Helmut
H
Warzecha
Klaus-Dieter
KD
Neudörfl
Jörg
J
Griesbeck
Axel G
AG
Mlinarić-Majerski
Kata
K
Basarić
Nikola
N
D004563:Electrochemistry; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D010777:Photochemistry; D010797:Phthalimides / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet
D010797:Phthalimides