Influence of substituents in the salicylaldehyde-derived Schiff bases on vanadium-catalyzed asymmetric oxidation of sulfides
2008 (English)In: Applied organometallic chemistry, ISSN 0268-2605, E-ISSN 1099-0739, Vol. 22, no 5, 253-257 p.Article in journal (Refereed) Published
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 H2O2 as oxidant in CH2Cl2 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.
Place, publisher, year, edition, pages
2008. Vol. 22, no 5, 253-257 p.
IdentifiersURN: urn:nbn:se:kth:diva-17521DOI: 10.1002/aoc.1386ISI: 000255693500003ScopusID: 2-s2.0-51349108362OAI: oai:DiVA.org:kth-17521DiVA: diva2:335565
QC 201005252010-08-052010-08-05Bibliographically approved