Application of a novel 1,3-diol with a benzyl backbone as chiral ligand for asymmetric oxidation of sulfides to sulfoxides (original) (raw)
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Journal of Chemical Sciences
The chiral metal complex produced in situ from (R)-6,6-Diphenyl-BINOL and Ti(O−i−Pr) 4 as a catalytic system for asymmetric sulfoxidation of aryl methyl and aryl benzyl sulfides in the presence of 70% aqueous TBHP as the oxidant has been investigated. The influence of variation of reagents mole ratios, temperature, solvent and oxidant was examined, and the optimized conditions were then used to oxidize a number of aryl methyl and aryl benzyl sulfides, producing sulfoxides in high enantiopurities (up to 90% ee) and good yields (up to 81%).
Tetrahedron: Asymmetry, 2002
Products with three new stereogenic centers were generated via sequential asymmetric dihydroxylation and sulfoxidation of homoallylic sulfides. The non-racemic homoallylic sulfoxides were prepared using chiral, vanadyl-based catalytic system with e.e. of up to 85%. Subsequently, these compounds were dihydroxylated with AD-mix system and gave products of low d.e.s (up to 40%). Recrystallization of l-diastereomers furnished both enantiomerically pure 1-phenyl-4-phenylsulfinylbutane-1,2-diols (X-ray), which are new and useful chiral building blocks. Further oxidation at sulfur produced the corresponding enantiomers of 1-phenyl-4-phenylsulfonylbutane-1,2-diol.
Tetrahedron Letters, 1998
In the asymmetric oxidation of methyl p-tolyl sulfide, (2a), and benzyl phenyl sulfide (2b) by TBHP, mediated by a titanium complex with enantiopure (R,R)-p,p'-disubstituted-l,2diphenylethane-l,2-diols, both the unsubstituted diol (R,R)-la and the p-OMe substituted diol (R,R)lb lead to sulfoxides of S configuration, with ee up to 99%. On the contrary the p-CF3 substituted ligand (R,R)-lc leads to significantly lower ee and in the case of 2a a reversal of asymmetric induction is observed.
Tetrahedron-asymmetry, 2006
Various chiral non-racemic β-ketosulfoxides, a class of compounds frequently used in asymmetric synthesis, were prepared in good yields by tert-butyl hydroperoxide oxidation of the corresponding sulfides in the presence of a complex between titanium and (S,S)-hydrobenzoin. The ee values of almost all of the purified products were >98%. As ascertained by X-ray analysis and/or by NMR spectroscopy, the use of the (S,S)-form of the ligand led to aryl β-ketosulfoxides with (RS)-configuration and to methyl phenacyl sulfoxide with the (SS)-configuration. Some of the aryl ketosulfoxides were subjected to reduction with DIBAL-H/ZnCl2 and the corresponding β-sulfinylalcohols with an (R,RS)-configuration produced.(R)-2-Naphthyl phenacyl sulfoxideC18H14O2SEe >98% (HPLC)[α]D25=+204.5 (c 1.01, CHCl3)Source of chirality: enantioselective oxidationAbsolute configuration: R(R)-p-Bromophenyl phenacyl sulfoxideC14H11BrO2SEe >98% (HPLC)[α]D25=+174.3 (c 1.00, CHCl3)Source of chirality: enantioselective oxidationAbsolute configuration: R(R)-o-Bromophenyl phenacyl sulfoxideC14H11BrO2SEe >98% (HPLC)[α]D25=+390.4 (c 1.01, CHCl3)Source of chirality: enantioselective oxidationAbsolute configuration: R
A short route to chiral sulfoxides using titanium-mediated asymmetric oxidation
Pure and Applied Chemistry, 1985
The asymmetric oxidation of sulfides by t-BuOOH was realized in presece of one equivalent of a chiral titanium complex prepared from Ti(OiPr)4/diethyl tartrate/H20 (1:2:1). tlany sulfoxides could be synthetized 7ith ee's up to 95%. The main results are presented as well as attempts to use catalytic amounts of the chiral titanium and to the extension of the scope of the reaction.
Journal of Molecular Catalysis A: Chemical, 2012
An efficient asymmetric oxidation of prochiral sulfides catalyzed by a series of simple in situ generated complexes based on chiral amino alcohol derived Schiff bases with Ti(Oi-Pr) 4 was carried out in presence of cheap and environmentally benign oxidant H 2 O 2 at 0 • C. Prochiral sulfides were converted to respective chiral sulfoxides efficiently (conversion, 93%; up to ee, 98%) with this system in 10 h at 0 • C. The present study demonstrated a significant role of steric influence of the substituent attached on both aryl and alkyl moiety on the enantioselectivity. Kinetic studies of the catalytic reaction showed first order dependence on substrate and catalyst whereas it is zero for the oxidant. Kinetic studies in combination with UV-vis. spectral studies were used to propose a catalytic cycle for the sulfoxidation reaction.