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

Various chiral non-racemic b-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 b-ketosulfoxides with (RS)-configuration and to methyl phenacyl sulfoxide with the (SS)-configuration. Some of the aryl ketosulfoxides were subjected to reduction with DIBAL-H/ZnCl2 and the corresponding b-sulfinylalcohols with an (R,RS)-configuration produced.