| N-Protected and un-protected 2-azetidinones, protolytically activated by superacidic trifluoromethanesulfonic acid, react with aromatic compounds to give beta-amino aromatic ketones in good to excellent yields (65--98%). Non-benzenoid aromatics (pyrrole and ferrocene) produced good yield (64--89%) of the corresponding ketones. The intramolecular reaction of N-aryl-2-azetidinones (Fries-type rearrangement), catalyzed by trifluoromethanesulfonic acid under mild conditions, gave the corresponding 2,3-dihydro-4-(1H)-quinolones in excellent yields (96--98%). A survey of protic and Lewis acid Friedel-Crafts catalysts revealed that trifluoromethanesulfonic acid was the only catalyst to efficiently activate protected and unprotected 2-azetidinones under such mild conditions.; The initial studies towards an efficient and practical total synthesis of hymenialdisine, a biologically important marine sponge metabolite isolated from the Great Barrier Reef sponges Axinella verrucosa and Acantella aurantiaca, is presented. The key steps proposed involve incorporation of the amino-imidazolin-4-one ring system utilizing an alpha,beta-unsaturated oxazolone and an intramolecular cyclization, to form the seven-membered ring skeleton, through a Bischler-Napieralski reaction or an isocyanate. |
