Trimethylsulfonium

Calculate the energy of proton transfer from trimethylsulfoxonium cation to its ylide, relative to that for trimethylsulfonium cation to its ylide, i.e. 

Epoxidation of aldehydes and ketones is the most profound utility of the Corey-Chaykovsky reaction. As noted in section 1.1.1, for an a,P-unsaturated carbonyl compound, 1 adds preferentially to the olefin to provide the cyclopropane derivative. On the other hand, the more reactive 2 generally undergoes the methylene transfer to the carbonyl, giving rise to the corresponding epoxide. For instance, treatment of P-ionone (26) with 2, derived from trimethylsulfonium chloride and NaOH in the presence of a phase-transfer catalyst Et4BnNCl, gave rise to vinyl epoxide 27 exclusively. ... 

The reaction mechanism of the DNA (cytosine-5)-methyltransferase-catalyzed cytosine methylation was investigated at the MP2 and DFT levels [98JA12895]. This system has been modeled by 1-methylcytosine 117, methylthiolate, and trimethylsulfonium. The cytosine methylation is initiated by an attack of the anionic methylthiolate at Cg of the cytosine ring (Scheme 77). The formation of the methylthiolate adduct 118 of the neutral 117 was found to be endothermic in the gas phase and in solution. However, the MP2 and DFT results differ... 

The formation of a further single bond between sulfur and carbon, as in the trimethylsulfonium cation, may be pictured as involving a 3sp3 unshared pair orbital on sulfur and an empty 2sp3 orbital on carbon in a methyl cation. Thus the three a bonds and the remaining unshared pair (in a 3sp3 orbital) in a trialkylsulfonium ion are distributed approximately tetrahedrally, i.e. the ion is pyramidal, with the sulfur atom at the apex (2). 

Compounds 242 when treated with trimethylsulfonium iodide under phase-transfer catalysis (PTC) conditions ( -Bu4XI, dichloromethane, 50% NaOH) provide mixtures of the corresponding 2-oxiranylvinyl benzotriazoles 243 and 18-83% yields of heteropentalenes 244. The ratio of these two main products is highly dependent on the R substituent (Scheme 29) <2004ARK(ii)109>. 

Y. Ishida, S. Wakamatsu, H. Yokoi, H. Ontani and S. Tsurge, Compositional analysis of polyunsaturated fatty acid oil by one step thermally assisted hydrolysis and methylation in the presence of trimethylsulfonium hydroxide, J. Anal. Appl. Pyrol., 49, 267 276 (1999). 

Epoxides are believed to be intermediates in the conversion of the enol ethers of 1,3-diketones (ketoaldehydes are less satisfactory) into 2,4-substituted furans by means of the trimethylsulfonium ylids. No epoxides could be isolated, however, nor was it necessary to use acid to effect cy-clization. Methoxydimethylsulfonium ylids were less efficient and tended to produce thiabenzene oxides instead, so Scheme 8 remains speculative.57 The use of thioenols instead of 1,3-diones is advantageous.233... 

The very rapid exchange reaction between dimethyl sulfide and MeSSMe2 (43) is accompanied by a much slower, and irreversible, reaction (47) between the same reagents that involves nucleophilic attack of the sulfide on one of the sulfonium methyl groups and that leads to the formation of trimethylsulfonium ion and dimethyl disulfide (Kim and Caserio, 1974). Other sulfides (RSCH3) react similarly to give RS(CH3)2. When the sulfide is trideuteriomethyl... 

Trifluoromethanesulfonic acid, Acyl chlorides, Aromatic hydrocarbons, 0375 Trimethylsulfonium chloride, 1303 Trimethylsulfoxonium bromide, 1299 Uronium nitrate, 0494... 

Trichlorophenol, 2107 Trifluoromethyl perchlorate, 0321 Trifluoromethylsulfm trifluoride, 0363 Trimethyl orthoformate, 1708 Trimethylsulfonium chloride, 1303... 

A rather more complex scheme is required for the preparation of a derivative that bears a trifluoromethyl substituent on one of the benzene rings. The scheme starts with the condensation of the nitrile group in (32-1) with phenyhnagnesium bromide to give the corresponding imine treatment with aqueous acid leads to the substituted benzophenone (32-2). The future methyl on one of the bridges is introduced in a sequence involving the addition of a trimethylsulfonium yhde. 

Condensation of the carbonyl group with the yUde from trimethylsulfonium iodide leads initially to an addition product. The anion formed on the carbonyl oxygen then internally displaces dimethyl sulfide to give an oxirane yielding epoxide (114-3). Reaction of that intermediate with a 1,2,4-triazine leads to an epoxide ring opening with the consequent incorporation of the second heterocyclic moiety. There is thus obtained fluconazole (114-4) [125]. 

A structurally unusual 3-blocker that uses a second molecule of itself as the substituent on nitrogen is included here in spite of the ubiquity of this class of compounds. Exhaustive hydrogenation of the chromone (13-1) leads to a reduction of both the double bond and the carbonyl group, as in the case of (11-2). The car-boxyhc acid is then reduced to an aldehyde (13-2) by means of diisobutylaluminum hydride. Reaction of that intermediate with the ylide from trimethylsulfonium iodide gives the oxirane (13-3) via the addition-displacement process discussed earlier (see Chapters 3 and 8). Treatment of an excess of that epoxide with benzylamine leads to the addition of two equivalents of that compound with each basic nitrogen (13-4). The product is then debenzylated by catalytic reduction over palladium to afford nebivolol (13-5) [16]. The presence of four chiral centers in the product predicts the existence of 16 chiral pairs. 

Reaction of cyclobutanones with trimethylsulfonium bromide in the presence of a base gave epoxides.65,332 The opposite configuration with respect to the epoxide is achieved65 when using this strategy vs. the epoxidation of the corresponding methylenecyclobutane with a peracid (see Section 5.1.2.2.). 

Another total synthesis of sufentanil has been described the cyclization of 2-(2-thienyl)ethylamine with allyl-trimethylsilane and formaldehyde gives 4-hydroxy-1-[2-(2-thienyl)ethyl]piperidine, which is oxidized with oxalyl chloride in DMSO/dichloromethane to 1-[2-(2-thienyl) ethyl]piperidin-4-one. The epoxidation of this compound by means of trimethylsulfonium iodide and the sodium salt of DMSO yields the spiro-epoxide, which is opened with... 

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