Synthesis of novel beta-amino alcohols and their application in the catalytic asymmetric sulfoxidation of sulfides

Novel chiral norephedrine-based beta-amino alcohol ligands containing a thiophene ring were prepared from norephedrine and substituted furan carbaldehydes (methyl- or ethyl-substituted) and used in combination with VO(acac)(2) for the asymmetric oxidation of aryl methyl sulfides using H2O2 as an oxidant. Amino alcohol derived Schiff bases 4,5a-b gave higher enantiomeric excesses than amino alcohol-derived reduced Schiff based ligands 6,7a-b. Of these chiral ligands, (1S,2R)-5b and (1S,2R)-7b gave high yields (90%) with moderate to high enantioselectivities (78%, 96% ee, respectively). The oxidation of other aryl methyl sulfides with (1S,2R)-5b and (1S,2R)-7b as ligands afforded the corresponding sulfoxides in 60-89% yields and with 92-99% ee. (C) 2013 Elsevier Ltd. All rights reserved.