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. (C) 2014 Elsevier Ltd. All rights reserved.