Iridium-Catalyzed Asymmetric Ring-Opening of Oxabenzonorbornadienes with Phenols

A novel iridium-catalyzed asymmetric ring-opening (ARO)
reaction
of oxabenzonorbornadienes with a variety of phenols was reported,
which afforded the corresponding trans-2-phenoxy-1,2-dihydronaphthalen-1-ol
products in high yields with moderate to excellent enantioselectivities
(up to 98% ee) under mild conditions. The trans products are formed
via the enantioselective cleavage of a bridgehead carbon–oxygen
bond in 1 followed by SN2 nucleophilic attack
by phenols. The effects of various bisphosphine ligands, Ag (I) salts,
ammonium halides, bases, and solvents on the yield and enantioselectivity
of the reaction were also investigated. The trans-configuration of
the product 2a was confirmed by X-ray crystal structure
analysis. A possible mechanism for the present catalytic reaction
was proposed.