Iridium-Catalyzed Asymmetric Ring-Opening of Oxabicyclic Alkenes with Carboxylic Acids

A novel iridium-catalyzed asymmetric ring- opening of oxabicyclic alkenes with a variety of carboxylic acids was reported, which afforded the corresponding trans-carboxylic acids 1-hydroxy-1,2-dihydro-naphthalen- 2-yl ester products in good yields with moderate enanti- oselectivities under mild conditions. The trans products are formed via the enantioselective cleavage of a bridgehead carbon-oxygen bond in 1 followed by SN2 0 nucleophilic attack by carboxylic acids. The effects of various bis- phosphine ligands, Ag(I) salts, ammonium halides, bases, and solvents on the yields and enantioselectivities of the reaction were also investigated. The theoretical analysis of stability and hydrogen bond for 1-hydroxy-1,2-di- hydronaphthalen-2-yl 4-chlorobenzoate 2a were performed using the density functional theory B3LYP methods. The trans-configuration of the product 2a was confirmed by X-ray diffraction analysis. A possible mechanism for the present catalytic reaction was proposed.