Oxidative synthesis of ortho-quinones from hydroxy-PAHs by stabilized formulation of 2-iodoxybenzoic acid (SIBX)

Abstract

Polycyclic aromatic phenols (PAPs or hydroxy-PAHs) are conveniently converted into their corresponding ortho-quinones using commercially available stabilized iodoxybenzoic acid (SIBX). SIBX provides a safer and commercially available alternative to IBX and displays the same selectivity with comparable or better yields in the oxidative dearomatization of phenols to ortho-quinone, including examples where formation of para-quinones is feasible. This ortho-selectivity from all positions of a hydroxy-group allowed for simple synthesis of the prerequisite hydroxy-PAHs by either photochemical cyclization of stilbenes or Pt-catalyzed cycloisomerization. The later synthesis involved a four-step sequence where suitably substituted biphenyls were prepared by Suzuki-Miyaura cross-coupling, followed by the Corey–Fuchs protocol and cycloisomerization by a catalytic amount of PtCl2. 2- and 4-methylphenanthene were also prepared for the first time using this method.