Novel catalytic enantioselective protonation (proton transfer) in Michael addition of benzenethiol to α-acrylacrylates: synthesis of (S)-naproxen and α-arylpropionic acids or esters

A novel synthesis of optically active 2-phenylpropionic acids or esters via catalytic enantioselective protonation in the Michael addition of benzenethiol to 2-phenylacrylates is described; the synthetic utility is further demonstrated by the asymmetric synthesis of (S)-Naproxen.