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doi:10.1016/S0040-4039(03)00614-2 
Copyright © 2003 Elsevier Science Ltd All rights reserved.
Amine-promoted cyclocondensation of highly substituted aromatic nitrile oxides with diketones
Received 6 February 2003;
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Abstract
Base-promoted cyclocondensation of hindered nitrile oxides and cyclic diketones affords highly functionalized, sterically-encumbered isoxazole products in good yield. The mild reaction conditions (NEt3, EtOH) are tolerant to a wide variety of functionality and permit the preparation of precursors to complex polycycles typically inaccessible via direct, intermolecular carbon---carbon bond forming reactions. The ability to effect the cyclocondensation reaction with a catalytic amount of amine points to the intermediacy of an ammonium enolate as a key reactive species. A convenient, single step preparation of crystalline, stable nitrile oxides from the corresponding oximes enhances the advantages of this methodology for the preparation of functionalized polycycles.
Keywords: nitrile oxide; cyclocondensation; benzophenone; organocatalytic; coleophomone
