Schiff-base ligands carrying two elements of chirality: Matched-mismatched effects in the vanadium-catalyzed sulfoxidation of thioethers with hydrogen peroxide

✍ Scribed by Alexander H. Vetter; Albrecht Berkessel

• Book ID: 104258875
• Publisher: Elsevier Science
• Year: 1998
• Tongue: French
• Weight: 233 KB
• Volume: 39
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(98)00084-7

✦ Synopsis

Eight chiral Schiff-base ligands were prepared from (S)-tert.-leucinol and four chiral, racemic salicylic aldehydes. The resulting pairs of diastereomers were separated by preparative HPLC and applied to the vanadium-catalyzed asymmetric sulfoxidation of thioethers with hydrogen peroxide. The product enantioselectivities revealed matched-mismatched effects that depended strongly on the structures of the chiral salicylic aldehydes. In particular, thioanisole and 2-bromothioanisole could be oxygenated in almost quantitative yields and with enantiomeric excesses up to 78 % ee. The latter values are the highest ones ever achieved for these substrates using transition metal catalysts and hydrogen peroxide as terminal oxidant.