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.

Graphical abstractAn effective method for the catalytic asymmetric epoxidation of aliphatic enones using a catalyst prepared from dibutylmagnesium and dialkyl tartrates, formulated as 6, is reported. In addition, an optimization study of the Bolm system for catalytic asymmetric sulfide oxidation using VO(acac)2 and H2O2 confirms that the ligand 12 is optimal. Figure optionsDownload full-size imageDownload as PowerPoint slide