Enantioselective epoxidation of styrene using in-situ generated dimethyldioxirane and dimeric homochiral Mn(III)-Schiff base complex catalyst

Abstract

The enantioselective epoxidation of styrene using in-situ generated dimethyldioxirane (DMD) and dimeric homochiral Mn(III)-Schiff base catalyst 1 has been explored. The parameters evaluated were olefin/oxidant molar ration, catalyst loading, reaction temperature and presence of nitrogen coordinating co-catalysts. Conversions of more than 99% and enantiomeric excess 66% were obtained. The selectivity is complete towards styrene oxide using 2 mol% catalyst loading, 1.36 mmol KHSO 5 in 8 ml of water, absence of co-catalyst and 17 °C as reaction temperature. Furthermore, the catalyst could be recycled up to three times with slightly decrease of catalytic activity due mainly to the physical loss of the catalyst during the recovery step and at a lesser extent as a consequence of its oxidative degradation.