Iridium-Catalyzed Asymmetric Addition of Thiophenols to Oxabenzonorbornadienes

A highly efficient asymmetric ring addition reaction of oxabenzo­norborna­dienes with thiophenols using an iridium/(S)-xyl-binap catalyst is developed. This catalyst system overcomes catalyst poisoning and background reactions and allows the formation of exclusive thiol addition products in high yields (up to 97% yield) with excellent enantioselectivities (up to 98% ee). Particularly noteworthy is that no competitive ring-opened side products are observed. X-ray crystal structure analysis confirmed the adduct is solely in the exo-configuration.