Cyclization of N-(propargylic)hydroxylamines catalyzed by AgBF4 afforded the corresponding 4-isoxazolines in good yields. Copper salts were found to promote the further transformation to acylaziridines. The combined use of AgBF4 and CuCl realized direct transformation of N-(propargylic)hydroxylamines into cis-acylaziridines.
The stereoselective direct transformation of N-(propargylic)hydroxylamines into cis-2-acylaziridines was achieved by the combined use of AgBF4 and CuCl. Copper salts were found to promote the transformation of the intermediary 4-isoxazolines into 2-acylaziridines and both 3-aryl- and 3-alkyl-substituted 2-acylaziridines could be prepared by using this method. Furthermore, subsequent 1,3-dipolar cycloaddition of azomethine ylides that were generated in situ from the intermediary 2-acylaziridines with maleimides was achieved in a stereoselective one-pot procedure to afford the corresponding 2-acylpyrrolidines, which consisted of an octahydropyrrolo[3,4-c]pyrrole skeleton.
Selective Transformation of N-(Propargylic)hydroxylamines into 4-Isoxazolines and Acylaziridines Promoted by Metal Salts. -AgBF4 is found to be an efficient catalyst for the cyclization of the title propargylic hydroxylamines (I) into isoxazolines (II). These isoxazolines rearrange into cis-ocylaziridines (III) on treatment with Cu-salts. Direct stereoselective formation of cis-aziridines (III) from hydroxylamines (I) is achieved by combined use of a AgBF 4 /CuCl catalyst system. -(WADA, N.; KANEKO, K.; UKAJI*, Y.; INOMATA, K.; Chem. Lett. 40 (2011) 5, 440-442, http://dx.doi.org/10.
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