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The acyliminium cations derived from 4-vinyloxy- or 4-acyloxy-azetidin-2-ones in the presence of Lewis acids can alkylate nucleophilic arenes bound to the β-lactam nitrogen atom through methyloxy, or methylthio tethers. The reactions smoothly proceed to afford the corresponding 3-oxa- or 3-thia-4,5-benzocephams in a good yield. The sulfur atom can be easily removed by Raney nickel reduction to provide...
The Lewis acid-catalyzed intramolecular substitution reactions of 4-vinyloxy- or 4-acyloxy-azetidin-2-ones with nitrogen-bound allyl-, propargyl- and vinyl-silanes leading to the carbacephams or carbacephems, are reported. The formation of carbapenams was not observed. To illustrate the potential of these reactions to be carried out under solid-phase conditions, a synthesis of diastereomeric 5-vinyl-carbacephams...
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