Catalytic Asymmetric Oxidation oftert-Butyl Disulfide. Synthesis oftert-Butanesulfinamides,tert-Butyl Sulfoxides, andtert-Butanesulfinimines

Abstract

The first example of the catalytic asymmetric oxidation of tert-butyl disulfide (1) is described. The product, tert-butyl tert-butanethiosulfinate (2) is obtained with 91% enantiomeric excess in yields of ≥92% on scales as large as 1 mol. The application of H2O2 as stoichiometric oxidant in the presence of 0.25 mol % of VO(acac)2 and 0.26 mol % of a chiral Schiff base ligand, 6a, is both convenient and cost-effective. Thiosulfinate ester 2 is chemically and optically stable and serves as an excellent precursor to chiral tert-butanesulfinyl compounds by the stereospecific nucleophilic displacement of tert-butyl thiolate. Addition of LiNH2 in liquid ammonia and THF provides tert-butanesulfinamide (3; 91% yield). A single recrystallization provides enantiomerically pure 3 in 71−75% overall yield from disulfide 1. Enantiomerically pure thiosulfinate ester 2 also reacts readily and stereospecifically with Grignard reagents, organolithiums, lithium amides, and lithium imine salts to provide enantiomerically pure chiral sulfoxides, sulfinamides, and sulfinimines in good yield.

tert-Butanesulfinylthioether ligands: synthesis and application in palladium-catalyzed asymmetric allylic alkylation

“…Commercial grade solvents were dried and purified by standard literature procedures. The 1 H NMR (300 MHz) and 13 C NMR (75 MHz) spectra were recorded on a Brucker-300 spectrometer. Optical rotation data were recorded on a Perkin-Elmer Polarimeter-341.…”

“…The residue was purified by column chromatography with petroleum ether/EtOAc (4:1, V/V) to afford 7. 13 Under an argon atmosphere, to a solution of 7 (1.0 mmol) in THF (5 mL) was added dropwise either n-BuLi (0.5 mL, 1.25 mmol, 2.5 M solution in hexane) or LDA (1.1 mmol) at À78°C, and the mixture was stirred for 1 h at À50°C. Under an argon flow, elemental sulfur (S 8 ) (64 mg, 2.0 mmol) was added to the reaction mixture at À78°C, and the temperature was allowed to slowly warm to room temperature.…”

Synthesis Of Chiral Allylic Amines Via Palladium(0) Catalysed Allylations Of Allylic Carbonates With Chiral Sulfinamide Anions

“…The know chiral sulfinamides, (R)-12, (S)-12 and (S)-13, were prepared by the methods of Davis [13] and Ellman [14] or purchased from the Aldrich Chemical Company. These compounds were used to prepare the N-benzoyl and N-tert-butoxycarbonyl (NBoc) derivatives, (R)-14, and (S)-15 respectively, in good yields (83-85%) according to Scheme 3.…”

Synthesis of enantioenriched sulfoxides

“…69 It was found that when R 1 = t-butyl, optimal results were obtained. Investigations revealed that the substituent at R 2 played no steric role in the oxidation, however the electronic effects of this substituent were important, for example when R 2 = NO 2 or OMe, there was a decrease in the enantioselectivity of the oxidation.…”

“…Results obtained by Ellman 68,69 and Zhu 99 employing vanadium catalysts in asymmetric oxidation indicated that chloroform was a good solvent for asymmetric sulfide oxidations. Jackson reported that kinetic resolution was enhanced carrying out the reaction in chloroform rather than dichloromethane at 20 o C and kinetic resolution was improved even further by carrying out the reaction in chloroform at 0 o C (Scheme 90).…”