Iron-catalyzed tandem carbon–carbon/carbon–oxygen bond formation/aromatization of 2′-alkynyl-biphenyl-2-carbinols: a new approach to the synthesis of substituted phenanthrenes

An iron-catalyzed efficient synthesis of substituted phenanthrenes through tandem intramolecular C–C/C–O bond formations/aromatization of 2′-alkynyl-biphenyl-2-carbinols is reported. This method provides a novel, highly efficient, and straightforward route to 9,10-substituted phenanthrene in good to excellent yields. The present strategy involves tandem Fe(OTf)3-catalyzed generation of benzylic carbocation, 6-exo-dig cyclization of alkyne, carbon–oxygen bond formation, and aromatization steps in one pot.

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