Synthesis of Salicylaldimine Mono-Schiff Bases with a Pendant Benzo-10-aza15-crown-5 and Catalytic Epoxidation Performance of Their Mn(III) Complexes

The aza-crown ether substituted salicylaldimine mono-Schiff bases HL~(1) and HL~(2) were synthesized from benzo-10-aza-15-crown-5 via Mannich reaction, reduction and condensation. Their Mn(III) complexes were employed as models to mimic monooxygenase in catalytic epoxidation of styrene.The effect of the azacrown ether in the ligands of MnL_(2)()~1Cl and MnL_(2)()~2Cl on the catalytic activity were also examined through comparing with uncrowned analogue MnL_(2)()~3Cl. The results indicated that MnL_(2)()~1Cl and MnL_(2)()~2Cl containing two azacrown rings were superior to the uncrowned analogue MnL_(2)()~3Cl. The MnL_(2)()~2Cl containing two heptyloxyl groups showed the best activity, its conversion and selectivity were up to 52.6 % and 96.2% respectively at ambient temperature and pressure.