Bis-Sulfonium-ylide

It was shown that complexes 19 of the zwitterionic precursors of ortho-quinone methides and a bis(sulfonium ylide) derived from 2,5-di hydroxyl 1,4 benzoquinone46 were even more stable than those with amine N-oxides. The bis(sulfonium ylide) complexes were formed in a strict 2 1 ratio (o-QM/ylide) and were unaltered at —78 °C for 10 h and stable at room temperature under inert conditions for as long as 15—30 min (Fig. 6.18).47 The o-QM precursor was produced from a-tocopherol (1), its truncated model compound (la), or a respective ortho-methylphenol in general by Ag20 oxidation in a solution containing 0.50-0.55 equivalents of bis(sulfonium ylide) at —78 °C. Although the species interacting with the ylide was actually the zwitterionic oxidation intermediate 3a and not the o-QM itself, the term stabilized o-QM was introduced for the complexes, since these reacted similar to the o-QMs themselves but in a well defined way without dimerization reactions. 

FIGURE 6.18 Oxidation of ortAo-methylphenols to the corresponding ortho-quinone methide via transient zwitterionic intermediates that are stabilized by forming a complex 19 with the 2,5-dihydroxy[l,4]benzoquinone-derived bis(sulfonium ylide). 

FIGURE 6.19 Formula and molecular structure of the 2 1 complex 20, formed between the zwitterionic o-QM precursor derived from PMC (la) and a bis(sulfonium ylide). 

Patel, A. Netscher, T. Rosenau, T. Stabilization of ortho-quinone methides by a bis (sulfonium ylide) derived from 2,5-dihydroxy-[l,4]benzoquinone. Tetrahedron Lett. 2008, 49, 2442-2445. 

Pyridinium ylide is considered to be the adduct car-bene to the lone pair of nitrogen in pyridine. The validity of this assumption was confirmed by Tozume et al. [12J. They obtained pyridinium bis-(methoxycarbonyl) meth-ylide by the photolysis of dimethyl diazomalonate in pyridine. Matsuyama et al. [13] reported that the pyridinium ylide was produced quantitatively by the transylidalion of sulfonium ylide with pyridine in the presence of some sulfides. However, in their method it was not easy to separate the end products. Kondo and his coworkers [14] noticed that this disadvantage was overcome by the use of carbon disulfide as a catalyst. Therefore, they used this reaction to prepare poly[4-vinylpyridinium bis-(methoxycarbonyl) methylide (Scheme 12) by stirring a solution of poly(4-vinylpyridine), methylphenylsulfo-nium bis-(methoxycarbonyl)methylide, and carbon disulfide in chloroform for 2 days at room temperature. 

Kondo maintained his interest in this area, and with his collaborators [62] he recently made detailed investigations on the polymerization and preparation of methyl-4-vinylphenyl-sulfonium bis-(methoxycarbonyl) meth-ylide (Scheme 27) as a new kind of stable vinyl monomer containing the sulfonium ylide structure. It was prepared by heating a solution of 4-methylthiostyrene, dimethyl-diazomalonate, and /-butyl catechol in chlorobenzene at 90°C for 10 h in the presence of anhydride cupric sulfate, and Scheme 27 was polymerized by using a, a -azobisi-sobutyronitrile (AIBN) as the initiator and dimethylsulf-oxide as the solvent at 60°C. The structure of the polymer was confirmed by IR and NMR spectra and elemental analysis. In addition, this monomeric ylide was copolymerized with vinyl monomers such as methyl methacrylate (MMA) and styrene. 

On heating the sulfonium ylide 464 (R = H) the isomeric bis(methoxycarbonyl)methyl-thiophene 465 is formed. Thermolysis of the ylide 464 (R = Cl) yields the thienofuran 466. When heated in the presence of copper or rhodium catalysts, 464 (R = Cl) undergoes cleavage of the carbonsulfur bond resulting in the formation of carbenoid intermediates which can trapped with activated aromatic substrates or alkenes to yield the corresponding arylmalonates or cyclopropanes, respectively. 

The formation of desaurins from ketones, carbon disulfide, and base 1275,1281,1282,1285-1290 believed to involve nucleophilic attack on a thioketene by the dianion of a 1,1-dimercaptoalkene, as shown for the synthesis of 572. Related syntheses involve the use of thiophosgene instead of carbon disulfide and the use of diazoalkanes or phosphonium and sulfonium ylides instead of a ketone and base. Treatment of perfluoroiso-butylene with fluoride ion and elemental sulfur in a dipolar, aprotic solvent ° °° or with sources of anionic sulfur (potassium sulfide, sodium hydrosulfide,potassium thiocyanate,sodium thiosulfate, dithiocarbamate salts, dithiophosphate salts ) give the dimer (573) of bis(trifIuoromethyl)-thioketene. Similarly, other 2,4-bis(methylene)-l,4-dithietanes are obtained by treating 2,2-dichlorovinyl ketones with anionic sulfur re-... 

It appears that the methylmercapto groups in fc(SMe)2 behave as electron-withdrawing substituents [233]. The bis(sulfonium) salt [fc(SMc2 )2]FeCl4" has been obtained by complexation of the ylide C5H4-SMc2 with FeCl2 in THF [234]. 

The cyclopropanation of (E,E)- and ( ,Z)-bis(styryl) sulfones 7 with sulfonium ylides leads to the formation of tranj-bis-cyclopropanated products 8 only. The stereochemistry of addition of dimethyloxosulfonium methanide to (E,Z)- and ( , )-bis(styryl) sulfones is explained as follows. The addition results in an intermediate which may rotate in such a way that the aryl and sulfonyl groups assume a trans orientation leading finally to the products. 

Similarly, the trisulfanylcyclopropenylium ions 3 reacted with iminopyridinium ylides in dimethyl sulfoxide or with sulfonium ylides in tetrahydrofuran. In these reactions, double addition of the cyclopropenylium ion occurred to give the A,A -bis(cyclopropenylidene)urea derivatives 4. ... 

Durch Einwirkung von Acylierungsmitteln und Basen auf Monoacyl-sulfonium-ylide entstehen zahlreiche Bis-acyl-Ylide (65) in meist sehr guter Ausbeute [51, 59). 

Among the other developed approaches to novel P-ylides, the synthesis of a-sulfanyl-a-phosphonyl phosphonium ylides (58) in quantitative yields via the addition of two equivalents of trialkylphosphites to phosphonodithio-formates should be mentioned. The subsequent reaction of these ylides with alkyl or benzyl halides gives stabilized sulfonium ylides (59) while their heating (18-150 h, 110 °C) leads to a-sulfanyl methylene bis-phosphonates through protonation-dealkylation intramolecular reactions. The synthesis... 

Previously, the same author [52] reported that compounds containing the tricoordinated sulfur cation, such as the triphenylsulfonium salt, worked as effective initiators in the free radical polymerization of MMA and styrene [52]. Because of the structural similarity of sulfonium salt and ylide, diphenyloxosulfonium bis-(me-thoxycarbonyl) methylide (POSY) (Scheme 28), which contains a tetracoordinated sulfur cation, was used as a photoinitiator by Kondo et al. [63] for the polymerization of MMA and styrene. The photopolymerization was carried out with a high-pressure mercury lamp the orders of reaction with respect to [POSY] and [MMA] were 0.5 and 1.0, respectively, as expected for radical polymerization. 

In analogy to the properties of ordinary sulfonium salts, reaction of disulfonium dications with bases may lead to either a- or p-deprotonation. Deprotonation of the S-S dication formed during the Pummerer rearrangement of monosulfoxides of certain bis-sulfides 13, 59, 56 is a key step of the overall process. Furukawa and co-workers " also suggested that direct formation of disulfonium dication ylides occurred upon treatment of sulfinyli-mines of 14 and 41 with potassium tert-butoxide. Reaction of triflic anhydride with sulfoxide 100 affords sulfonium salt 102 through deprotonation of the corresponding S-S dication 101 (Scheme 39). ... 

---