Effective asymmetric oxidation of enones and alkyl aryl sulfides

Asymmetric epoxidation of aliphatic enones can be achieved with good conversions and high levels of enantiomeric excess using a catalyst, formulated as 6, derived from dibutylmagnesium and a range of dialkyl tartrates, with tert-butylhydroperoxide as the oxidant. This process works best with the addition of small amounts of water and 4 Å molecular sieves, and can be scaled up to good effect. Optimisation of Bolm and Bienewald's vanadium-based method for asymmetric oxidation of alkyl aryl sulfides by aqueous hydrogen peroxide using Schiff bases derived from tert-leucinol as ligands, confirmed that the ligand 12 derived from 3,5-diiodosalicylaldehyde is the optimum choice.