- Photochemistry of Heterocycles, 8. The Photoreaction of 2,5-Diaryl-1,3,4-oxadiazoles with 1,3-Dimethyluracils. A New and Simple Synthesis of 1,2,4,5-Tetrazines
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Upon UV-irradiation 2,5-diaryl-1,3,4-oxadiazoles 2a-g do not undergo (2+2)-cycloaddition with 1,3-dimethyluracil, but instead ring cleavage occurs to afford the benzoylhydrazones 3a-e as well as the decomposition products 4-6.With 6-chloro-1,3-dimethyluracil (1b) 3h is formed, which in turn photoeliminates benzoyl chloride to give the pyrazolopyrimidine 7.Saponification of 3a gives smoothly 5-benzoyl-1,3-dimethyluracil (photoselective 5-benzoylation). - A new and simple synthesis of 3,6-disubstituted 1,2,4,5-tetrazines from aroylhydrazines is described, employing the system triphenylphosphane/hexachloroethane/triethylamine.
- Farkas, Lajos,Keuler, Josef,Wamhoff, Heinrich
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p. 2566 - 2574
(2007/10/02)
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