Catalytic applications of F8BINOL: asymmetric oxidation of sulfides to sulfoxides

Influence of substituents in the salicylaldehyde‐derived Schiff bases on vanadium‐catalyzed asymmetric oxidation of sulfides

“…[4,5] Therefore, asymmetric oxidation of prochiral sulfides is an attractive subject in organic synthesis. In the past two decades, asymmetric oxidation of sulfides has been extensively investigated, either promoted by Ti(O-i-Pr) 4 -chiral tartrates [6,7] and chiral organic compounds such as chiral oxaziridines, [8,9] or catalyzed by transition metal complexes of various chiral ligands, such as ironporphyrins, [10,11] manganese-salens, [12,13] titanium-BINOL, [14,15] titanium-C2-symmetric diols, [16,17] zirconium-trialkanol amines, [18] and vanadium- [19 -21] and iron- [22] tridentate Schiff base catalyst systems. Among these catalyst systems for asymmetric sulfoxidation, Bolm's catalysts, that is, VO(acac) 2 -and Fe(acac) 3 -Schiff base systems, have received considerable attention in recent years because of three attractive advantages: (1) the simplicity, convenient preparation, and easy modification of chiral Schiff base ligands; (2) the utilization of cheap and environmentally benign terminal oxidant (H 2 O 2 ); and (3) the facile reaction conditions and easy workup.…”

Preparation and catalytic applications of partially fluorinated binaphthol ligands

“…Oxidative coupling of 2-naphthols can be promoted by several metal catalysts such as complexes of ruthenium [16], titanium [17], vanadium [18], manganese [19], copper [20], and iron [21]. Unfortunately, the widely used FeCl 3 -catalyzed reaction cannot be used in our case because the fluorinated 2-naphthol 16 reacts with FeCl 3 to give chlorinated product 17 (Scheme 4) [9].…”

“…We previously, reported the asymmetric oxidation of sulfides to sulfoxides using F 8 BINOL and its 7,7 0 -substituted derivatives [2,9]. Our initial results indicated that fluorine substitution is responsible for improved enantioselectivity where minimum amount of sulfone by-product is formed.…”

“…We recently, published the synthesis and catalytic applications of polyfluorinated BINOL ligands such as F 8 BINOL (3), an electronic isostere of BINOL [8]. In terms of catalytic applications, we explored the sulfoxidation [9] as well as the glyoxylateene reaction [10]. It was found that the (R)-F 8 BINOL-Ti system catalyzed the sulfoxidation reaction with higher enantioselectivity (89% in CH 2 Cl 2 ) than the (R)-BINOL-Ti system (7% in CH 2 Cl 2 and 22% in CCl 4 ) at 0.05 M concentration.…”

Synthesis of enantioenriched sulfoxides

“…33 Carrying out the reaction at room temperature, using chloroform as the solvent and CHP as the oxidising agent, 16 significantly outperformed 9 in terms of enantioselectivity and efficiency. Also significant is the stereoselectivity of the reaction, using 9 the R enantiomer is preferentially formed while using 16 the S enantiomer is preferentially formed.…”