First synthesis of the chiral mixed O/S ligands, 1,2-sulfinyl thiols: application as chiral proton sources in enantioselective protonations of enolates

A suitable method for the preparation of the chiral mixed O/S ligands 1,2-s ulfinyl thiols is described. These compounds have then been used as a chira l proton source in the enantioselective protonation of 2-methyl tetralone e nolate and the results are compared with those obtained from the analogous alcohols. A theoretical model is proposed to explain the different behavior s exhibited in the protonation reaction for each of these proton sources. C onfigurational assignments for the new chiral thiols have been carried out by means of X-ray analysis. (C) 2000 Elsevier Science Ltd. All rights reser ved.