The synthesis of chiral beta-ketosulfoxides by enantioselective oxidation and their stereocontrolled reduction to beta-hydroxysulfoxides

Various chiral non-racemic beta-ketosulfoxides, a class of compounds frequently used in asymmetric synthesis, were prepared in good yields by tert-butyl hydroperoxide oxidation of the corresponding sulfides in the presence of a complex between titanium and (S,S)-hydrobenzoin. The ee values of almost all of the purified products were > 98%. As ascertained by X-ray analysis and/or by NMR spectroscopy, the use of the (S,S)-form of the ligand led to aryl beta-ketosulfoxides with (R-S)-configuration and to methyl phenacyl sulfoxide with the (S-S)-configuration. Some of the aryl ketosulfoxides were subjected to reduction with DIBAL-H/ZnCl2 and the corresponding beta-sulfinylalcohols with an (R,R-S)-configuration produced.