General procedure

Enantioselective epoxidation in a neutral medium is made possible by using dioxirane and an optically active manganese(III) salt as catalyst.

Different enantiomeric products are obtained depending on which form of catalyst is being used.

Fig.1

Epoxidation of 6-cyano-2,2-dimethyl-2H-chromene.

The manganese salts have the following absolute configurations:

Fig.2

Absolute configurations of the maganese salts.