Approach to Spirocyclohexadienimines and Corresponding Dienones through Radical ipso Cyclization onto Aromatic Azides


  • We gratefully acknowledge financial support from MIUR (2006–2007 Funds for “Extending the Application of Organic Free Radicals to New Synthetic Methods”).


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Ipsoeasy: Cyclization of aryl radicals at the ipso-position of p-azido-substituted benzamides or 2-phenylacetamides results in effective production of spirocyclohexadieniminyl radicals through prompt elimination of molecular nitrogen by transient azidocyclohexadienyl radicals. The resultant iminyl radicals can be exploited for the synthesis of oxindoles or quinolones bearing spiro-cyclohexadienimine/cyclohexadienone rings (see picture, TTMSS=tris(trimethylsilyl)silane).