Effect of fifth coordination in catalytic epoxidation by a chiral manganese porphyrin

The effect of multifarious organic bases in chiral manganese porphyrin catalyzed enantioselective alkene epoxidation was investigated. For substituted pyridines, the enantioselectivity of cis-β-methylstyrene epoxidation follows a linear free energy relationship for pyridines bearing electron-donating groups. Compared to the case of no amine additive, a significant improvement in enantioselectivity from 43% ee to 81% ee for epoxidation of cis-β-methyl-styrene with a 86.5% stereospecificity were observed when DMAP and KHSO 5 were employed as axial ligand and oxidant respectively.