Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
Photochemistry and Photophysics of 3-(2-Isoxazolinyl)-phenylketones3-Benzoyl-Δ2-1,2-oxazolines (1-6) are formed by 1,3-dipolar cycloaddition between benzoylnitril-N-oxide (8) and dihydrofurane 9 or 1,3-dioxep-5-enes (10a-c). The preparative yields are small due to the competitive dimerization of the dipole 8. Two stereoisomers are obtained by using 2-substituted 1,3-dioxep-5-enes as dipolarophiles. The different steric position of the substituents in 3-6 gives rise to different spectral data. The synthesized ketones possess triplet states with a high degree of charge transfer character. Therefore, the ability to H-abstraction reaction from alcohols is small. For ketone 2 and methanol as H-donor a rate constant of kHMeOH = 4,1 · 102 M-1s-1 is determined. Also by electron transfer reactions with triethylamine and some onium compounds the reactivity of the T1 of the ketones 1-6 is less compared to those of nπ* excited ketones. The photolysis of the ketones takes place very unselectively and leads to a product mixture. The quantum yields for the decay of the ketones are 10-2 to 10-3.
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