Dimethyloxosulfonium methylide

Bravo et al. studied the reaction of various ylides with monooximes of biacetyl and benzil. Dimethylsulfonium methylide and triphenylarsonium methylide gave 2-isoxazolin-5-ol and isoxazoles, with the former being the major product. Triphenylphosphonium methylide and dimethyloxosulfonium methylide gave open-chain products (Scheme 135) (70TL3223, 72G395). The cycloaddition of benzonitrile oxide to enolic compounds produced 5-ethers which could be cleaved or dehydrated (Scheme 136) (70CJC467, 72NKK1452). 

Treatment of trimethyloxosulfonium iodide with sodium hydride generates dimethyloxosulfonium methylide according to the reaction. This reagent has the remarkable... 

Ruano has reported substrate-controlled asymmetric ylide aziridination by treatment of enantiopure sulfinyl imines 117 with dimethyloxosulfonium methylide 118 to form terminal aziridines [63], The chiral tert-butylsulfinyl group was shown... 

Double-bond compounds that undergo the Michael reaction (15-21) can be converted to cyclopropane derivatives with sulfur ylids. Among the most common of these is dimethyloxosulfonium methylid (109), which is widely used to... 

Aldehydes and ketones can be converted to epoxides in good yields with the sulfur ylids dimethyloxosulfonium methylid (60) and dimethylsulfonium methylid (61). For most purposes, 60 is the reagent of choice, because 61 is much less... 

Methylenecyclohexane oxide has been prepared by the oxidation of methylenecyclohexane with benzonitrile-hydrogen peroxide or with peracetic acid by treatment of 1-chlorocyclo-hexylmethanol with aqueous potassium hydroxide and by the reaction of dimethylsulfonium methylide with cyclohexanone. This reaction illustrates a general method for the conversion of ketones and aldehydes into oxiranes using the methylene-transfer reagent dimethyloxosulfonium methylide. The yields of oxiranes are usually high, and the crude products, in most cases, are of sufficient purity to be used in subsequent reactions (e.g., rearrangement to aldehydes) without further purification. 

Starting from the chiral oxazolone 632 derived from l,2-(9-isopropylidene-D-glyceraldehyde, diastereoselective cyclopropanation has been reported to occur with dimethyloxosulfonium methylide or (diethylamino)phenyloxosulfonium... 

A stereoselective total synthesis of dendrobatide toxin 251 D was developed by Overman et al.237) involving an epoxidation of the (S)-proline derivative (237) to furnish the oxirane (238) as major product. In their approach towards the total synthesis of the same natural product Thomas et al.238) investigated the stereoselectivity of the epoxide formation from (S)-5-acetylpyrrolidin-2-one and dimethyloxosulfonium methylide. A diastereoselectivity of d.s. 50-60% was achieved 238. ... 

The same intermediate occurs in the Lehmann method463 for converting the methiodides of phenolic Mannich bases into 2,3-dihydrobenzo-furans, through reaction with dimethyloxosulfonium methylide. Thus, o-benzoquinone methide (207) leads to 2,3-dihydrobenzofuran according to Scheme 4. Similarly, 2-naphtholgives l,2-dihydronaphtho[2,l-6]furan through 208 and 209, formed and rearranged in situ.i6i The reaction has been applied to the synthesis of polycyclic benzofurans.483,485... 

Isoflavones (388) and dimethyloxosulfonium methylide gives 2,3-dihydro-2,3-methano-4-benzopyrones with 2-vinyl-3(2H)-benzofura-nones (389) as by-products.837... 

Dimethyloxosulfonium methylide reacts with the triketone (212) to give the fused 2-hydroxymethylenedihydropyran (213) (76H(4)1755). The reaction is thought to proceed through a zwitterion and the epoxide as indicated in Scheme 41. Intramolecular nucleophilic attack leads to the dihydropyran and the overall process may be regarded as a transfer of methylene from the sulfur ylide. 

It is beneficial in terms of yield to convert an a,/3-unsaturated ketone into the cyclopropyl ketone using dimethyloxosulfonium methylide. The epoxide, formed as above, is rearranged during chromatography on silica gel. The corresponding pent-2-ene-l,5-diols are also formed, presumably through hydration of the cation, and these may be dehydrated to the pyran with p-toluenesulfonic acid (74JCS(P1)1674). 

A solution of dimethyloxosulfonium methylide in DMSO (30 ml) was prepared under argon from trimethyloxosulfonium iodide (9.6 mmol) and NaH (60% dispersion in oil, 9.6 mmol) at room temperature. After stirring for 90 min (the evolution of hydrogen ceased) the solution of the ylide was added dropwise to a solution of the vinyl sulfoxide (3.2 mmol) in DMSO (25 ml) over a 30 min period. The reaction mixture was stirred at room temperature for 14h, poured into an ice water mixture, and extracted twice with ether. The ether layers were washed twice with water, dried over anhydrous MgS04 and evaporated in vacuo to give a crude cyclopropyl sulfoxide as a white solid. Flash chromatography (silica, ethyl acetate/n-hexane (25 75) gave the (7 c,Ss) isomer (1.02g, 82%), m.p. 227-228°C and the (Sc,5s) isomer (0.17g, 14%), m.p. 202-203°C. 

Corey s procedures for the conversion of ketones into epoxides using sulfonium or oxosulfonium ylides have found widespread use in organic synthesis. An attempt to apply the method to methyl 2-benzoylbenzoate, however, gave 4-phenylisocoumarin in 52% yield when dimethyloxosulfonium methylide was used. 

Dimethyloxosulfonium methylide - known as the Corey-Chaykovsky Reagent - is a valuable alternative to dimethylsulfonium methylide and can be generated from trimethylsulfoxonium iodide. 

A recently reported novel asymmetric aziridination route involves the action of methylene transfer reagents on chiral sulfinimines 97, whereby the selectivity is conferred by the asymmetric sulfinyl center. The stereochemical outcome of this reaction is dependent upon the methylene transfer reagent. Thus, dimethyloxosulfonium methylide provided predominantly isomer 98, whereas the use of dimethylsulfonium methylide led to the formation of 99 as the major product [95TL295]. 

The ring-expansion reaction of epoxides was first reported by Okuma and coworkers, to produce less-substituted oxetanes (Scheme 7.2) [11]. The nudeophilic attack by dimethyloxosulfonium methylide is proposed to react with the less-... 

The intermediacy of such oxaspiropentanes has been proposed in the addition of diazomethane to ketonesi0) and in the reaction of dimethyloxosulfonium methylide with a-haloketones55). In contrast to phosphorous ylides, sulfur ylides usually condense with carbonyl compounds to yield epoxides, thus reaction of the N,N-dimethylaminophenyloxosulfonium cyclopropylide 99 with cyclohexanone produced the dispiroepoxide 100 which rearranged to the spiro [3.5] nonan-l-one 101 upon isolation by gas chromatography, Eq. (29) S6). 

Table 26. Reaction of N-Sulfinylimines with Dimethylsulfonium Methylide (n = 0, Reagent A) and Dimethyloxosulfonium Methylide (n = 1, Reagents B and C)...

N-Sulfinylaziridines 181 are formed as mixtures of diastereoisomers from (Ss)-179 and dimethyloxosulfonium methylide (180).38,95,96 The diastereoselectivity can... 

Alkyl thiol anions displace halogens from halocodides to give corresponding alkylthiocodides. 192 Dihydrocodeinone (78) has been reported 200 to react with sodium dimethyloxosulfonium methylide (dimsyl sodium), giving the 6-oxirane (91), which opened under reducing conditions to the methyl carbinol, 92, an analgesic similar in potency to codeine. 

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