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Influence of substituents in the salicylaldehyde‐derived Schiff bases on vanadium‐catalyzed asymmetric oxidation of sulfides
Author(s) -
Liu Haibin,
Wang Mei,
Wang Ying,
Yin Ran,
Tian Wei,
Sun Licheng
Publication year - 2008
Publication title -
applied organometallic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.53
H-Index - 71
eISSN - 1099-0739
pISSN - 0268-2605
DOI - 10.1002/aoc.1386
Subject(s) - chemistry , schiff base , vanadium , thioanisole , salicylaldehyde , medicinal chemistry , aryl , catalysis , ligand (biochemistry) , moiety , sulfide , enantioselective synthesis , polymer chemistry , stereochemistry , organic chemistry , biochemistry , alkyl , receptor
A series of chiral Schiff bases ( L 1 – L 5 ) with different substituents in the salicylidenyl unit were prepared from condensation of 3‐aryl‐5‐ tert ‐butylsalicylaldehyde derivatives and optically active amino alcohols. Bromination of 3‐phenyl‐5‐ tert ‐butylsalicylaldehyde gave an unexpected product 3‐(4‐bromophenyl)‐5‐bromosalicylaldehyde, from which the corresponding Schiff base ligands L 6 and L 7 , derived from ( S )‐valinol and ( S )‐ tert ‐leucinol, respectively, were prepared. Ligands L 1 – L 7 were applied to the vanadium‐catalyzed asymmetric oxidation of aryl methyl sulfides. Under the optimal conditions, the oxidation of the thioanisole with H 2 O 2 as oxidant in CH 2 Cl 2 catalyzed by VO(acac) 2 ‐ L 1 – L 7 gives good yields (74–83%) with moderate enantioselectivity (58–77% ee). Ligand L 7 , containing a 4‐bromophenyl group on the 3‐position and a Br atom on the 5‐position of the salicylidenyl moiety, displays an 80–90% ee for vanadium‐catalyzed oxidation of methyl 4‐bromophenyl sulfide and methyl 2‐naphthyl sulfide. Copyright © 2008 John Wiley & Sons, Ltd.