SYNTHESIS OF 1-AZAXANTHONES AND 1-AZATHIOXANTHONES BY Yb(OTf)(3)/TfOH CO-CATALYZED INTRAMOLECULAR FRIEDEL-CRAFTS REACTION

[摘要]：Intramolecular Friedel-Crafts cyclization of phenoxypyridine acids (3a-3j) and phenythiopyridine acids (4a-4i) to form 1-azaxanthones (1a-1j) and 1-azathioxanthones (2a-2i), respectively, was efficiently promoted by Yb(OTf)(3)/TfOH as co-catalysts. And a number of substrates could be cyclized in moderate to good yields.

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