Asymmetric synthesis of trans-disubstituted aryl-vinyl epoxides: a p-methoxy effect

It was found that trans-aryl-vinyl epoxides could be synthesized with 77–100% conversion from conjugated aldehydes (which could also behave as Michael acceptors and lead to cyclopropanes) and chiral sulfonium salts with eeʹs ranging from 95 to 100%. When a p-methoxy group was present on the arylsulfonium salt, the epoxide was the sole product whatever the solvent.