TMSCl-promoted selective oxidation of sulfides to sulfoxides with hydrogen peroxide

Selective oxidation of sulfides to sulfoxides is achieved using H₂O₂ and TMSCl as the promotor. Aromatic and aliphatic sulfides are oxidized to sulfoxides in excellent yields and in short reaction times. Different functional groups including ketone, alkene, ester, and alcohol are tolerated.     

A general and selective zinc-catalyzed oxidation of sulfides to sulfoxides

A general zinc-catalyzed oxidation of sulfides to sulfoxides has been developed. All the reactions proceeded at room temperature. Hydrogen peroxide was used as a green oxidant. Twenty-one examples of sulfoxides were prepared in moderate to excellent yields.     

Efficient asymmetric oxidation of sulfides and kinetic resolution of sulfoxides catalyzed by a vanadium-salan system

The asymmetric oxidation of sulfides to chiral sulfoxides with hydrogen peroxide in good yield and high enantioselectivity has been catalyzed very effectively by chiral vanadium-salan [N,N'-alkyl bis(salicylamine)] complex. The salan ligand shows results superior in terms of reactivity and enantioselectivity to those of salen [N,N'-alkylene bis(salicylideneimine)] analogue, and provides the sulfoxide with opposite configuration. The high enantioselectivity of this reaction is the direct result of the asymmetric oxidation. The efficient kinetic resolution of racemic sulfoxides catalyzed by the vanadium-salan system is also described.     

Activation of superoxide by boron trifluoride: chemoselective and efficient oxidation of sulfides to sulfoxides via tetrafluorodiboronperoxide

Activation of superoxide with boron trifluoride in dry acetonitrile can facilitate highly chemoselective and efficient oxidation of sulfides to corresponding sulfoxides at ice-water bath in excellent yields without any interference in the presence of ketone, olefin, ether, and hydroxyl functionalities. This new method also offers further advantages of a short reaction time, no overoxidation to sulfones, and none of complex catalysts and toxic metallic compounds used. A tetrafluorodiboronperoxide intermediate formed in situ from this new process is proposed.     

Safe oxidation of sulfides into sulfoxides using SIBX

SIBX is a stabilized (i.e., nonexplosive) formulation of the λ⁵-iodane 2-iodoxybenzoic acid IBX that can be used as a suspension in various organic solvents to oxidize safely sulfides into sulfoxides. Most yields are comparable to those obtained using IBX or other iodanes such as PhIO and PhIO₂. An asymmetric version of this SIBX-mediated sulfoxidation was performed in high chemical yield and moderate enantioselectivity by simple addition of an external chiral source.     

An efficient solvent free catalytic oxidation of sulfides to sulfoxides with hydrogen peroxide catalyzed by a binaphthyl-bridged Schiff base titanium complex

A titanium binaphthyl-bridged Schiff base complex proved to be an efficient catalyst for the hydrogen peroxide oxidation of aromatic and aliphatic sulfides to the corresponding sulfoxides in satisfactory yields under solvent-free conditions.     

Copper-catalyzed asymmetric oxidation of sulfides

Copper-catalyzed asymmetric sulfoxidation of aryl benzyl and aryl alkyl sulfides, using aqueous hydrogen peroxide as the oxidant, has been investigated. A relationship between the steric effects of the sulfide substituents and the enantioselectivity of the oxidation has been observed, with up to 93% ee for 2-naphthylmethyl phenyl sulfoxide, in modest yield in this instance (up to 30%). The influence of variation of solvent and ligand structure was examined, and the optimized conditions were then used to oxidize a number of aryl alkyl and aryl benzyl sulfides, producing sulfoxides in excellent yields in most cases (up to 92%), and good enantiopurities in certain cases (up to 84% ee).     

Chiral synthesis of indolizidines 209D and 167B via asymmetric oxidation of sulfides and sulfoxides

Chiral synthesis of indolizidine natural products (?)-209D and (?)-167B, as well as their antipodes, has been achieved through asymmetric oxidation of racemic thio-substituted indolizidines to the chiral sulfoxides and sulfones followed by Raney nickel reduction.     

Copper catalyzed oxidation of sulfides to sulfoxides with aqueous hydrogen peroxide

Copper(II) complex 1 catalyzes the oxidation of sulfides to sulfoxides with 30% H₂O₂ in high yields. Addition of a catalytic amount of TEMPO to the reaction mixture enhances the conversion and selectivity. Complex 1 can be recycled without loss of activity.     

Catalytic enantioselective oxidation of sulfides to sulfoxides with a renewable hydroperoxide

The catalytic asymmetric oxidation of prochiral sulfides can be conveniently performed by using an easily accessible and renewable furyl hydroperoxide in the presence of the chiral Ti(O-i-Pr)₄/BINOL/H₂O system.     

The mechanism of permanganate oxidation of sulfides and sulfoxides

Coupled-cluster (CCSD) and density functional computations are used to investigate historically competing mechanisms for the permanganate oxidation of sulfides and sulfoxides. The calculations all lead to a mechanism of 1,3-dipolar cycloaddition of permanganate, as opposed to historical mechanisms of attack of the sulfur atom by one O or by Mn. Such a mechanism, reminiscent of ozonolysis, may prevail in most permanganate oxidations. The ab initio activation enthalpies are in reasonable agreement with the experimental data; the ab initio activation entropies are not, possibly because of problems with Eyring equation assumptions.     

Tetracyanoethylene oxide not only oxidizes sulfides to sulfoxides but also reduces sulfoxides to sulfides

It was found that tetracyanoethylene oxide not only oxidizes sulfides to sulfoxides but also reduces sulfoxides to sulfides with generation of two molecules of carbonyl cyanide. The reaction thus also functions as a new method for generation of carbonyl cyanide.     

Erratum to: Catalyst-free oxidation of sulfides to sulfoxides and diethylamine catalyzed oxidation of sulfides to sulfones using Oxone as an oxidant

Research on Chemical Intermediates -     

Highly enantioselective oxidation of sulfides to sulfoxides by a new oxaziridinium salt

The new oxaziridinium salt 5 (R2 = TBDPS) is an effective reagent for the highly enantioselective oxidation of sulfides to sulfoxides with up to >99% ee and good yields. As such, it represents a new valuable nonmetallic alternative to the existing methods for asymmetric sulfoxidation.     

Effective oxidation of sulfides to sulfoxides with hydrogen peroxide under transition-metal-free conditions

A "green" highly selective oxidation of organic sulfides to the corresponding sulfoxides was developed using hydrogen peroxide and glacial acetic acid under transition metal-free and mild conditions. The oxidation procedure is very simple and the products are easily isolated in excellent yields (90-99%).