| Abstract
| - Azomethine ylide generation from the oxazolium salt22 and PhSiH3/CsF affords complexproductsderived from the initial cycloadduct 23 via three competingpathways. Colorless intermediates24−27 have been detected, and their oxidationproducts 10, 28, and 29 have beenidentified.Nucleophilic activation of the oxazolium salt 22 isreported using the organic-soluble benzyltrimethylammonium cyanide. This variation affords the unstablecycloadduct 32, which undergoesaromatization via a single pathway involving 24 and27, and DDQ oxidation gives the indoloquinone10 in an improved 63% yield. Lower yields usingPhSiH3/CsF or NaCN activation methods areattributed to the heterogeneous conditions and interception of theazomethine ylide by unreactedoxazolium salt.
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