Atropo- and diastereoselective construction of tetracyclic biphenylazepinium salts derived from aminoalcohols: use as catalysts in enantioselective asymmetric epoxidation.

A range of new biphenylazepinium salt organocatalysts effective for asymmetric epoxidation has been developed incorporating an additional substituted oxazolidine ring, and providing improved enantiocontrol in alkene epoxidation over the parent structure. Starting from enantiomerically pure aminoalcohols, tetracyclic iminium salts were obtained as single diastereoisomers through an atroposelective oxazolidine formation