Allyl sulphoxides reactions

The ethylaluminium dichloride-catalyzed reaction of p-toluenesulphinyl chloride with alkenes 136 successfully applied191 for the synthesis of allylic sulphoxides 137 (equation 74) may also be regarded formally as a reaction of sulphinyl chlorides with compounds containing active hydrogen atom. Treatment of an alkene 136 with one equivalent each of ethylaluminium dichloride and p-toluenesulphinyl chloride at room temperature gave the corresponding 137. This reaction is very general and proceeds in... 

The allyl sulphenate-allyl sulphoxide rearrangement is a general reaction and is applicable to structurally diverse allyl alcohols204,205 (Table 13). Mechanistically, it represents a typical example of a [2,3]-sigmatropic rearrangement as shown by the detailed investigations of Mislow and Braverman and their coworkers. 

Treatment of (—)-(S)-276 with allyl Grignard reagents gives optically active allylic sulphoxides 288. This reaction, however, involves an allylic rearrangement via transition state 289 as evidenced by Mislow and his collaborators362 (equation 160). 

The reaction of the phenylsulphinyl allylic lithium a-carbanion 342 with oxiranes was found by Guittet and Julia to give, after rearrangement and desulphurization, dihydroxy-dienes 343427 (equation 197). Demoute and coworkers have described the alkylation reaction of a very sophisticated 2-alkenyl sulphoxide 344 as a part of the total synthesis of a juvenile hormone 345428 (equation 198). Since the allylic sulphoxide carbanion has an ambident character, the alkylation may occur sometimes also at the y-position. This direction of alkylation is observed in the case of acyclic allylic sulphoxide anions 346, and results in the formation of the corresponding allylic sulphoxide 347 and vinylic sulphoxide 348423 (equation 199). 

Sulphoxides and selenoxides undergo syn elimination under thermal conditions. A 1,4-elimination of sulphenic acid from an allyl sulphoxide leads to dienes (equation 20)50. Precursor sulphoxides are generated by oxidation of corresponding sulphides. This reaction, however, did not give good results when applied to more complicated systems51. 

The conjugated thionium ylids are prepared by the Pummerer reaction of an allyl sulphoxide, with trimethylsilyl triflate in the presence of ethyl diisopropylamine, and give products of ketone allylation [equation (52)... 

The reactions shown above involve the main chain, but it is possible that sulphur-containing cross-links present in a vulcanizate are also sites for oxidative attack. Little is known about such processes except by analogy with simpler sulphides. The general thermal instability of allylic sulphoxides suggests that monosulphide cross-links may undergo the following reactions ... 

Treatment of olefins with toluenesulphinyl chloride and ethylaluminium dichloride in ether at room temperature gives allylic sulphoxides via a formal ene reaction (Scheme 57)/ The Lewis acid acts both as a catalyst for the rearrangement and as a proton scavenger, reacting with the hydrogen chloride produced to give ethane and aluminium chloride. 

Reaction of alkynols 156 with benzenesulphenyl chloride afforded either the vinylacety-lene sulphoxides 157 or the allene sulphoxides 158 depending upon the substitution pattern of alkynols 156. Vinylacetylene sulphoxides 157 result from a [2,3]-allylic rearrangement of the sulphenate ester 159 (equation 88). In the case of the cyclic... 

The carbanions of 1-alkenyl sulphoxides 400 also react with carbonyl compounds to give the corresponding condensation products384 (equation 237). Solladie and Moine have used this type of reaction in their enantiospecific synthesis of the chroman ring of a-tocopherol 401. Addition of the lithio reagent 402 to the aldehyde 403 affords the allylic alcohol 404 in 75% yield as a sole diastereoisomer481 (equation 238). 

Allyl p-tolyl sulphoxide 535 reacts with sodium methoxide in methanol by initial prototropic isomerization and subsequent addition of methanol to give 536 (equation 333). Protic solvents are photochemically incorporated by the open chain olefinic bond of trans methyl )S-styryl sulphoxide 537 in a Markovnikov regiospecificity (equation 334). Mercaptanes and thiophenols add to vinyl sulphoxides in a similar manner (compare also Reference 604 and Section IV.B.3) to give fi-alkylthio(arylthio)ethyl sulphoxides 538 (equation 335). Addition of deuteriated thio-phenol (PhSD) to optically active p-tolyl vinyl sulphoxide is accompanied by a low asymmetric a-induction not exceeding 10% (equation 336) . Addition of amines to vinyl sulphoxides proceeds in the same way giving )S-aminoethyl sulphoxides in good to quantitative yields depending on the substituents at the vinyl moiety When optically active p-tolyl vinyl sulphoxides are used in this reaction, diastereoisomeric mixtures are always formed and asymmetric induction at the p- and a-carbon atoms is 80 20 (R = H, R = Me) and 1.8 1 (R = Me, R = H), respectively (equation 337) ... 

The allyl 2-nitrophenyl sulphoxide is apparently not an intermediate in this reaction as the MS of the latter compound is dominated by a cleavage reaction giving rise to C3H5+, whereas the ions corresponding to a loss of the HSC>2 radical apparently are of low intensity86. Thus, it was concluded that the double oxygen transfer to sulphur most probably should be formulated as a concerted reaction86. 

Reduction of nitroalkanes RNO2 with samarium(II) iodide, obtained from samarium and 1,2-diiodoethane, yields either alkylhydroxylamines RNHOH or alkylamines RNH2, depending on the amount of the reagent434. The base-catalysed reaction of nitroalkanes with phenyl(vinyl) sulphoxide (399) yields the conjugate adducts 400, which fragment to allylic nitro compounds 401 on thermolysis435. 

Hydrogen-bond donors have the ability to enhance the selectivities and rates of organic reactions. Examples of catalytic active hydrogen-bond donor additives are urea derivatives, thiourea derivatives (Scheme 10, Tables 12 and 13) as well as diols (Table 14). The urea derivative 7 (Scheme 9) increases the stereoselectivity in radical allylation reactions of several sulphoxides (Scheme 10)171. The modest increase in selectivity was comparable to the effects exerted by protic solvents (such as CF3CH2OH) or traditional Lewis acids like ZnBr2172. It was mentioned that the major component of the catalytic effect may be the steric shielding of one face of the intermediate radical by the complex-bound urea derivative. 

Thione-S-oxides react regiospecifically with allyl and benzylsilanes in the presence of a stoichiometric amount of tetra-n-butylammonium fluoride to produce allyl and benzyl sulphoxides [8], cf. the analogous fluoride initiated reaction of thio-ketones and dithiocarboxylic esters with silanes [9, 10]. The yields of sulphoxides... 

Allyl ethers are also formed under PTC conditions (see Expt 5.73). These ethers are stable under moderately acidic and basic conditions. Deprotection is achieved by treatment with potassium t-butoxide in dimethyl sulphoxide, which results in rearrangement to the corresponding prop-l -enyl ether, followed by reaction with a mercury(n) chloride/mercury(n) oxide reagent mixture.78... 

The reactions of hydrogen peroxide with vanadate have been of interest for many years. Much of the early work was concerned with the function of peroxovanadates as oxygen transfer agents. Alkenes and similar compounds such as allyl alcohols can be hydroxylated or epoxidized. Even alkanes can be hydroxylated, whereas alcohols can be oxidized to aldehydes or ketones and thiols oxidized to sulphones or sulphoxides. Aromatic molecules, including benzene, can be hydroxylated. The rich chemistry associated with the peroxovanadates has, therefore, led to extensive studies of their reaction chemistry. To this end, x-ray diffraction studies have successfully provided details of a number of peroxovanadate structures. 

---