Sulfides, allyl benzyl

Nucleophilic addition to a, -unsaturated sulfones has long been known. For example, treatment of divinyl sulfone with sodium hydroxide has been known to afford bis( -hydroxyethyl) sulfone "", while the reaction of a- and -naphthyl allyl sulfones and allyl benzyl sulfone " with alkali hydroxide or alkoxide gave -hydroxy or alkoxy derivatives. In the latter reaction, the allyl group underwent prototropy to the 1-propenyl group, which in a subsequent step underwent nucleophilic attack . Amines, alcohols and sulfides are known to add readily to a, -unsaturated sulfones, and these addition reactions have been studied widely. In this section, the addition of carbon nucleophiles to a, ji-unsaturated sulfones and the reactions of the resulting a-sulfonyl carbanions will be examined. 

This I04 -5i02 reagent is not very elective in the oxidation of sulfides into sulfoxides. However, sulfuryl chloride adsorbed wet silica gel is an excellent reagent for this transformatim (equation 5). High yields of methyl aryl, diaryl, allylic. benzylic and dialkyl sulfoxides are thus obtainable. The procedure commends itself by its simplicity and its extension to thioacetals provides a good, quantitative re-... 

Hydrogen peroxide attacks the sulfur atom in preference to the double bond in allyl phenyl sulfide and allyl benzyl sulfide to give allyl phenyl sulfoxide (64%) and allyl benzyl sulfone (85%), respectively. Olefinic sulfones may also be obtained by dehydrohalogenation of /3-haloalkyl sulfones prepared by this method. Oxidation of sulfides has been utilized in the preparation of sulfones containing other common functional groups such as the amide, tro, amino, and ester groups. 

Methyl Allyl Sulfide, Methyl Benzyl Sulfide and Phenyl Allyl Sulfide... 

Etherification of hindered tribromophenol with allyl bromide Reaction of sodium sulfide with benzyl chloride Reaction of amino acids and methanesulfonyl chloride Dichlorovinylation of carbazole in solid-liquid system... 

Too intensively stabilized by delocalization, 9-allylthio-9-fluorenyllithium proves inert. In contrast, allyl benzyl sulfide, after metalation with -butyllithium, rearranges smoothly at -15 °C. Several pathways are taken simultaneously as an in-depth investigation by Jean Biellmann et has revealed (Scheme 1-298). The species... 

Scheme 1-298. Four eoexisting reaction channels available for the rearrangement of lithiated allyl benzyl sulfide.

Two efficient syntheses of strained cyclophanes indicate the synthetic potential of allyl or benzyl sulfide intermediates, in which the combined nucleophilicity and redox activity of the sulfur atom can be used. The dibenzylic sulfides from xylylene dihalides and -dithiols can be methylated with dimethoxycarbenium tetrafiuoroborate (H. Meerwein, 1960 R.F. Borch, 1968, 1969 from trimethyl orthoformate and BFj, 3 4). The sulfonium salts are deprotonated and rearrange to methyl sulfides (Stevens rearrangement). Repeated methylation and Hofmann elimination yields double bonds (R.H. Mitchell, 1974). 

Various S-nucleophiles are allylated. Allylic acetates or carbonates react with thiols or trimethylsilyl sulfide (353) to give the allylic sulfide 354[222], Allyl sulfides are prepared by Pd-catalyzed allylic rearrangement of the dithio-carbonate 355 with elimination of COS under mild conditions. The benzyl alkyl sulfide 357 can be prepared from the dithiocarbonate 356 at 65 C[223,224], The allyl aryl sufide 359 is prepared by the reaction of an allylic carbonate with the aromatic thiol 358 by use of dppb under neutral condi-tions[225]. The O-allyl phosphoro- or phosphonothionate 360 undergoes the thiono thiolo allylic rearrangement (from 0-allyl to S -allyl rearrangement) to afford 361 and 362 at 130 C[226],... 

Depending on the choice of transfer agent, mono- or di-cnd-functional polymers may be produced. Addition-fragmentation transfer agents such as functional allyl sulfides (Scheme 7.16), benzyl ethers and macromonomers have application in this context (Section 6.2.3).212 216 The synthesis of PEG-block copolymers by making use of PEO functional allyl peroxides (and other transfer agents has been described by Businelli et al. Boutevin et al. have described the telomerization of unsaturated alcohols with mercaptoethanol or dithiols to produce telechelic diols in high yield. 

The most popular method for generation of a-thio-carbanion (migration terminus) is direct lithiation (deprotonation) with alkyllithium or lithium amide. These deprotonation methods are widely applicable to various substrates, not only benzyl or allyl sulfides , but also dithioacetals 142 which form 143 (equation 83), and a phosphonate substituted system 144 which gives 145 (equation 84). ... 

Allylic and benzylic alcohols were oxidized to aldehydes or ketones with BnPhsPHSOs in refluxing CHsCN. The yield increased in the presence of bismuth chloride in a catalytic amount. Selective oxidation of various alcohols under solvent free conditions was also reported Interestingly, benzyl alcohols were oxidized selectively to benzaldehydes in very high yield (95-100%) when reacted with BnPhsPHSOs (1.2 eq.) and AICI3 (1 eq.) in the presence of an equimolar amount of 2-phenethyl alcohol, diphenyl carbinol or methyl phenyl sulfide (equation 72). 

An interesting cleavage of a carbon-sulfur bond in benzylic and allylic sulfides derived from 5-mercapto-l -phenyl-1 //-tetrazole has been reported [326]. The overall reaction is an alkylation a to a carbonyl group. 

Ally lie iodides. Allylic and benzylic alcohols (primary and secondary) are converted into the corresponding iodides by reaction with Nal and BF3 etherate in 70-95% yield. The same system converts sulfoxides to sulfides in 90-98% yield. 

Most sulfur compounds resist the action of active Mn02 at low temperature. For instance, organic sulfides resist active Mn02 during the oxidation of allylic and benzylic alcohols.57 Thiols, being sulfur compouds with a greater oxidation sensitivity, are oxidized to disulfides.56... 

Odourless and non-volatile organosulfur compounds grafted to an imidazolium ionic liquid scaffold has been synthesized. The sulfoxides have been used for an efficient oxidation of primary allylic and benzylic alcohols into aldehydes and secondary alcohols to ketones under Swern oxidation conditions and the corresponding sulfides can be recovered and recycled.110... 

The successful extension of this asymmetric reaction to the use of allyl halides (instead of benzyl halides) was also reported by the Metzner group [208]. The desired vinyl oxiranes were formed in a one-pot reaction starting from an allyl halide and an aromatic aldehyde in the presence of a sulfide, e.g. 215, and sodium hydroxide as base. A 9 1 mixture of tert-butanol and water was used as solvent. 

Oxidation of primary and secondary alcohols. In contrast to dimethyl sulfide-NCS (4, 88-90), which oxidizes both primary and secondary alcohols, diisopropyl sulfide-NCS can effect selective oxidation of these substrates. At 0° it oxidizes only primary alcohols to aldehydes, but at —78° it oxidizes only secondary alcohols to ketones. However, allylic or benzylic alcohols are oxidized at either temperature. 

Sulfides. Benzylic or allylic alcohols react with thiols in the presence of zinc iodide (0.5 equiv.) in 1,2-dichloroethane at 20° to form sulfides in yields generally of 80-90%. 

Problems can arise at the last stage due to difficulties in die isolation of die aldehyde and/or preferential vinyl sulfide formation. Nonetheless, the method has some potential Sulfoxides are prone to thermal elimination, and this has been used by Trost in his mediod, which can also be used for the oxidation of primary amines (Scheme 14). The procedure is limited to benzylic and allylic bromides. 

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