One of the components of the "chalcone lab", namely, the individualized, three-step synthesis of the 3,5-diarylisoxazole followed by isomer determination using 13C NMR or mass spectroscopy is presented as an expansion of the one-step chalcone synthesis. The two added steps in the three-step synthesis involve addition of bromine to the double bond of the chalcone followed by conversion of the dibromide to the isoxazole by reaction with hydroxylamine. The chalcone dibromide is prepared by addition of bromine to the chalcone in acetic acid. The dibromide is heated with hydroxylamine hydrochloride in the presence of KOH for 5-10 minutes to give the isoxazole. The predictable fragmentation pattern that is observed in the mass spectra of 3,5-diarylisoxazoles can also be used to determine which isoxazole isomer is in hand.
|Original language||English (US)|
|Number of pages||5|
|Journal||Journal of Chemical Education|
|Publication status||Published - Sep 1 2006|
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