Asymmetric Hydroxylative Phenol Dearomatization Promoted by Chiral Binaphthylic and Biphenylic Iodanes

Abstract

AbstractThe long‐standing quest for chiral hypervalent organoiodine compounds (i.e., iodanes) as metal‐free reagents for asymmetric synthesis continues. Although remarkable progress has recently been made in organoiodine‐catalyzed reactions using a terminal oxidant in stoichiometric amounts, there is still a significant need for “flaskable” chiral iodane reagents. Herein, we describe the synthesis of new iodobinaphthyls and iodobiphenyls, their successful and selective DMDO‐mediated oxidation into either λ3‐ or λ5‐iodanes, and the evaluation of their capacity to promote asymmetric hydroxylative phenol dearomatization (HPD) reactions. Most notably, a C2‐symmetrical biphenylic λ5‐iodane promoted the HPD‐induced conversion of the monoterpene thymol into the corresponding ortho‐quinol‐based [4+2] cyclodimer (i.e., bis(thymol)) with enantiomeric excesses of up to 94 %.