Sulfonium methylides

Ring expansion of activated aziridines (43) with sulfur ylides also provides a synthesis of azetidines (75JOC2990, 58BSF345, 81CC417). The highly reactive sulfonium methylide (44 R = R = H) undergoes further reaction with the azetidines (46), but the reaction is satisfactory for substituted methylides. The less reactive sulfoxonium methylide (45 R = R = H)... 

One of the most remarkable recent extensions of the chemistry of aurated ylides was the multiauration of dimethyl(oxo)sulfonium methylide using trimethyl(oxo)sulfonium salts and (Ph3P)Au(acac) in different... 

The development of new methods for carbon-caihon bond formation is at the heart of organic synthesis. The most desirable methods are those that are easily practiced at scale, operate near ambient temperature, and that do not require strong acid or base. David C. Forbes of the University of South Alabama and Michael C. Standen of Synthetech in Albany, OR report (Organic Lett. 5 2283,2003) that the crystalline salt 2, which can be stored, smoothly converts aldehydes to epoxides, without any additional added base. The reaction is apparently proceeding by the loss of CO, from 2 to give the intermediate sulfonium methylide. 

Azetidines.x N-Arylsulfonyl-2-phenylazetidincs (2) can he prepared from N-arylsulfonyl-2-phenylaziridines (I) by inethylene transfer from dimethyloxo-sulfonium methylide. 

The reaction of optically active (l-diethoxyphosphoryl)vinyl p-tolyl sulfoxide (20) with sulfur ylides has provided the corresponding cyclopropanes (21) in high yields (g) (Scheme 10).52,53 With fully deuterated dimethyl(oxo)sulfonium methylide, (CD3)2 S(0)CD2, the cyclopropanation reaction occurred in a highly diastereoselective... 

N-Metkylation ofindoles Indoles can be selectively N-methylated by dimethyl-sulfonium methylide in THF at room temperature. 

In chemical oxidation or reduction the redox reagent and the substrate often form a covalent or ionic bond, for example, an ester in chromic acid oxidation [8], a sulfonium methylide in the Swern oxidation [9], cyclic esters in the svn dihydroxylation with OSO4 [10], or in the selenium dioxide oxidation of ketones and aldehydes [11]. In electrochemical processes the substrate must diffuse from the bulk of the solution to the electrode and compete there with other components of the electrolyte by competitive adsorption for a position at the electrode surface [12]. The next step is then generation of the reactive intermediate by electron transfer at the electrode that reacts with a low activation energy to the products. In chemical oxidations or reductions one finds a reductive or oxidative elimination of the intermediate with a higher activation energy. 

Sulfonium methylides can also be prepared from sulfides by treatment with Me3SiCH20Tf followed by desilylation with CsF. ° This method allows the regioselective generation of sulfonium ylides (i.e. 140), which would not form under equilibrium deprotonation conditions (c/. 139 141 Scheme 21). ... 

Volatron, F., Eisenstein, O. Wittig versus Corey-Chaykovsky Reaction. Theoretical study of the reactivity of phosphonium methylide and sulfonium methylide with formaldehyde. J. Am. Chem. Soc. 1987, 109, 1-4. 

With substrates containing a nucleophilic group sited close to a carbonyl group, on reaction with the sulfonium methylide (21) the intermediate epoxides are not isolated and instead heterocycles are generally obtained. For instance, o-aminophenyl ketones (50) react with the ylide (21) to yield the benzopyrroles (51) via the epoxides (52) (Scheme 20). 

Thus far, discussion has centered around the reaction of alkenes with a source of electrophilic oxygen as a route to epoxides [the C=C + O protocol]. However, a second general approach is represented by the reaction of carbonyl compounds with amphophilic carbon centers [the C=0 + C protocol]. For example, sulfonium yhdes are known to convert aldehydes and ketones to epoxides much recent work has focused on asymmetric induction using this methodology, a topic which has been the subject of a concise review in the past year <04ACR611>. As an illustration, the D-mannitol derived chiral sulfide 42 serves as a useful chiral auxiliary in the sulfonium methylide epoxidation of aldehydes to provide terminal monosubstituted oxiranes (e.g., 44) in fair to excellent yield and good enantiomeric excess <04CC1076>. 

Reactions. In a reaction reminiscent of methylene transfer with dimethyloxo-sulfonium methylide, EDSA reacts with ,/)-unsaturatcd aldehydes and ketones in aprotic solvents to give cyclopropanes in 65-90% yield.1 EDSA reacts with ,/3-unsaturated esters to give esters of acyclic polybasic acids.2... 

Methylation Diazomethane-Boron fluoride etherale. Dimethylcopperlithium. Dimethyl-sulfonium methylide. Iodine Methyl iodide. Methyl-(tri-n-butylphosphine) copper complex. Silver perchlorate. Simmons-Smith reagent. Sodium hydride. 

OXIRANES (Dimethylamino)phenyl-oxosulfonium methylide. Dimethyl-sulfonium methylide. (Dimethyl sulfoxide, derived reagent (b)). Methylene bromide-Lithium. Methylphenyl-N-p-tohienesulfonylsulfoximine. 

The synthesis of lettucenin A was achieved by Monde et al. and this is described in Scheme 14. Indanone (146) was treated with dimethyl sulfonium methylide to give an aldehyde and allyl alcohol, which were... 

DesilyltUive reactions. A new version of the Peterson olefination employs a combination of ethyl trimethylsilylacetate, an aldehyde, and CsF. Similarly, epoxide synthesis from carbonyl compounds avoids strongly basic conditions by using [Ph SCHjSiMej]" TfO as a source of the sulfonium methylide. ... 

Eine zu (22) analoge Zwischenstufe (27) konnte den Reaktionsverlauf zwanglos erklaren. Mit dem Dimethyl-sulfonium-methylid (3) wurde da-gegen nur o-Methoxy-benzaldehyd erhalten. 

Ohne Angaben fiber seine Reaktionsfahigkeit wurde das aus Dinitro-methan, Dimethylsulfoxyd und Acetanhydrid in 36 % Ausbeute zugang-liche Dinitro-dimethyl-sulfonium-methylid (101) beschrieben (J7), das sich gegenfiber Dinitromethan... 

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