Efficient access to orthoquinols and their [4 + 2] cyclodimers via SIBX-mediated hydroxylative phenol dearomatization.

SIBX, the nonexplosive formulation of the lambda5-iodane 2-iodoxybenzioc acid (IBX), safely and efficiently mediates the hydroxylative dearomatization of various 2-alkylphenols and napthols into orthoquinols or their [4 + 2] cyclodimers. Reactions are typically run at room temperature using SIBX as a suspension in THF. Using these conditions, natural products such as the cyclodimer of the terpene carvacrol and, for the first time, the shikimate-derived (+/-)-grandifloracin were prepared in one step from their respective phenolic precursor.