From sulfur ylids

The simplest sulfur ylids are formed from sulfonium salts 69 by deprotonation in base. These ylids react with carbonyl compounds to give epoxides.18 Nucleophilic attack on the carbonyl group 70 is followed by elimination 71 of dimethylsulfide 72 and formation of the epoxide 73. You should compare diagram 71 with diagram 23 in chapter 15. The phosphonium ylid reacted by formation of a P-0 bond and an alkene in the Wittig reaction. The sulfonium compound reacts by formation of a C-O bond 71 as the S-O bond is much weaker than the P-0 bond. The sulfonium salt 69 can be reformed by reaction of 72 with Mel. 

So what has this got to do with cyclopropanes If sulfur ylids react with enones either the epoxide 74 or the cyclopropane 76 may be formed.19 The general rule is that sulfonium ylids from 69 give epoxides but sulfoxonium ylids give cyclopropanes 76. 

When sodium hydroxide was used as nucleophile, salt 3c was rapidly converted to alkyne 63. This alkyne now features only a single stereocenter, and this is evident from its spectra. Its structure was initially assigned incorrectly, but the alkyne structure (63) has been rigorously established by X-ray crystallography. It is curious that azide and hydroxide should attack on the periphery of the TTF ring system, while the bulkier malonate anion attacks internal carbons. It is also intriguing that none of the observed modes of attack give rise to the sulfur ylid 64, which should be more stable than 61. 

Epoxides can be converted directly to episulfides by treatment with NH4SCN and ceric ammonium nitrate.Diazoalkanes, treated with sulfur, give episulfides.It is likely that R2C=S is an intermediate, which is attacked by another molecule of diazoalkane, in a process similar to that shown in 16-46. Thioketones do react with diazoalkanes to give episulfides.Thioketones have also been converted to episulfides with sulfur ylids.Carbenes, such as the dichlorocarbene from CHCI3 and base, react with thioketones to give an... 

Proton removal from mixed cyclopropylisopropylphosphonium salts to form phos-phoranes gave only the products 182 resulting from proton removal from the isopropyl groupsHowever, sulfur ylids such as 183 may be prepared and have found wide application in synthesis Equilibrium acidities of cyclopropanes substituted with a variety of sulfonyl-type substituents have also been measured ... 

An interesting approach to azasugars (e. g. 116 in O Scheme 31) from the epoxsides built at the anomeric centers of unprotected carbohydrates was presented recently [78]. Such epoxides (e.g. 115) were obtained with very high selectivity hy reaction of the corresponding hemi-acetals (e. g. 114) with sulfur ylid (O Scheme 31). This reaction is applicable for various sugar aldehydes [79]. 

A photochemical route to benzo[u]quinolizin-4-ones (73) from 1-styryl-2-pyridones has been reported by Mariano et al.8S Acid was found to be essential and the cyclization was thought to proceed through the excited enol 72, with eventual oxidation by air or by added iodine. Benzo[b]-quinolizin-6-one (74)76 and the corresponding imine (75)86 have been prepared by cyclization of 2-(2-carboxybenzyl)pyridine and 2-cyanobenzyl-pyridine, respectively. Eicher and Hansen87 have reported two routes to a benzo[c]quinolizin-l-one (76) (Eqs. 41 and 42) and one to the 1-thione 77 (Eq. 41). Treatment of quinoline N-oxide with 1,1-dicyanoalkenes also led to benzo[c]quinolizin-l-ones (Eq. 43),88 while the same A-oxide with the sulfur ylid 78 gave a benzo[c]quinolizin-3-one.89... 

A) and used in organic synthesis. a-Lithio sulfides give useful carbanion reactions and sulfur ylids can be formed (secs. 8.6, 8.8.B). The difficulties in preparing primary and secondary amines by traditional methods (from halides or tosylates via reaction with imides or azides, sec. 2.7) make the hydroboration-amination sequence a mild and useful alternative for the synthesis of amines. 

A number of reactions have been developed involving sulfur ylids formed by attack of sulfur nucleophiles on arynes. For example, alkyl o- and / -(phenylthio)benzoates are obtained in modest yield by reaction of benzyne (from anthranilic acid) with the corre-... 

A polymeric sulfur ylid reagent containing dimethylsulfonium methylide was synthesized by Tanimoto et al. (1967) from a copolymer of p-vinylphenylmethyl thioether, styrene, and DVB, according to Scheme 12-17. The reagent was used for the synthesis of epoxides from the carbonyl compounds. It was claimed that, in addition to simplifying the procedure for isolation of the products, the polymeric reagent is nonodorous and convenient to handle, compared to the noxious, volatile, low-molecular-weight sulfides used in classical syntheses. 

The chemistry of sulfur ylids as diazocarbonyl equivalents has been covered from the viewpoint of their generation and use in metal-catalysed reactions." The contribution of molecular modelling on the understanding of alkene metathesis has been detailed from the perspective of the properties of transition metal complexes, the theoretical description of metal carbene interaction and the computations carried out on these species. ... 

The mobility of the proton in position 2 of a quaternized molecule and the kinetics of exchange with deuterium has been studied extensively (18-20) it is increased in a basic medium (21-23). The rate of exchange is close to that obtained with the base itself, and the protonated form is supposed to be the active intermediate (236, 664). The remarkable lability of 2-H has been ascribed to a number of factors, including a possible stabilizing resonance effect with contributions of both carbene and ylid structure. This latter may result from the interaction of a d orbital at the sulfur atom with the cr orbital out of the ring at C-2 (21). 

Similar cycloadditions between thiirene dioxides and 1,3-dipoles generated in situ give heterocycles which result from either loss of sulfur dioxide or from the three-membered ring opening of the initially formed adduct (e.g. 174). Such cycloadditions with nitrilium imides (173a) and nitrile ylids (173b) are illustrated in equation 69175. 

Potts and co-workers have used phosphorus pentasulfide and pyridine as a standard reagent for constructing annelated diphenylthiophene rings from o-dibenzoyl compounds. Many of these annelated thiophenes can be written only in the tetracovalent sulfur or ylid dipolar form (96) and are thus termed nonclassical 123 other examples, particularly of the synthesis of non-classical thienoisothiazoles, have been reported by Gotthardt.124... 

The proton in the thiazolium ring is relatively acidic (pATa about 18) and can be removed by even weak bases to generate the carbanion or ylid (see Box 11.8). An ylid (also ylide) is a species with positive and negative charges on adjacent atoms this ylid is an ammonium ylid with extra stabilization from the sulfur atom. 

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