Allyl sulphoxides rearrangement

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. 

A detailed study of the mechanism of the allyl sulphoxide-sulphenate rearrangement and its uses in synthesis has been reported. Rates of steroidal allyl sulphoxide rearrangements are influenced by chirality at sulphur, and configurational aspects established for compounds of this... 

The spontaneous rearrangement of allyl p-toluenesulphenates to allyl sulphoxides was independently recorded by Mislow and coworkers and Braverman and Stabinsky. Mislow and colleagues201 have demonstrated that simple allyl alcohols such as 149, on conversion to the corresponding lithium alkoxides followed by treatment with arenesulphenyl chlorides, may be smoothly transformed at room temperature via the sulphenate esters into allylic sulphoxides 150 (equation 83). Braverman and Stabinsky202 have found that when the more reactive trichloromethanesulphenyl chloride is treated with allyl alcohol and pyridine in ether at — 70°, it affords trichloromethyl allyl sulphoxide and not allyl trichloromethanesulphenate as reported by Sosnovski203 (equation 84). 

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). 

Nucleophilic addition to allenyl sulphoxides 547 proceeds across the a, /(-double bond to produce the corresponding )3-substituted allylic sulphoxides which undergo readily a [2,3]-sigmatropic rearrangement affording substituted allyl alcohols (equation 345). Under proper basic conditions, the initially formed allylic sulphoxides can rearrange to the corresponding vinyl sulphoxides which can be elaborated to 2,4-dienones 549 (equation 346) and a-ketosulphoxides (equation 347) . ... 

Where X is S or Se and Y is oxygen or a carbanionic site. The rearrangement of allyl sulphoxides to allyl sulphenates is an example. 

An example of a [2,3]-sigmatropic rearrangement involving an allyl sulphoxide was studied by Evans and Andrews in 1974 [22] (Scheme 5.20) ... 

Thermal and mercury(ii)-catalysed [3,3]sigmatropic rearangement of allylic trichloroacetimidates and allylic pseudo-ureas" e.g. geraniol, linalool) are useful for the 1,3-transposition of hydroxy- and amino-groups the former is synthetically preferred. The [2,3]sigmatropic rearrangement of allylic sulphoxides has been used to effect an alkylative 1,3-carbonyl transposition of enones (e.g. carvone). ... 

One of the most widely used allyl alcohol syntheses uses the Evans-Mislow rearrangement (39, arrows) of allyl sulphoxides17) (Scheme 1). Since the allyl sulphoxide is usually made from some allylic electrophile by substitution and oxidation, this strategy requires a specific allyl cation equivalent. 

The allyl sulphide (223) was obtained peracid oxidation furnished the sulphoxides (224). These sulphoxides rearranged on treatment with diethylamine to give, after deprotection, 7-hydroxy ... 

Trimethylsilylallylic alcohols of the type (81) react with phenylsulphenyl chloride to give unstable allylic sulphoxides which rearrange spontaneously at room temperature hydrolysis then furnishes a,unsaturated aldehydes (Scheme 40). ° ... 

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. 

Evans has extended his studies on the synthetic equivalence of allylic sulphoxides and the rearranged allylic alcohols further evidence of this equivalence has been demonstrated. 

Methods previously used in the D-arabino-serles (Vol. 22, p.17-18) have been applied to the synthesis of derivatives (21) of 3-deoxy-D-lyxo-heptulosonic acid.22 Treatment of thioglycoside (22), prepared by acylation of a sulphur-stabilized C-1 carbanion as described previously for similar systems (Vol. 21, p.131-132), as indicated in Scheme 8 gave rise to the 4-acetamido-4-deoxy derivative (23) related to DAHP a [2,3]-sigmatropic rearrangement of an allyl sulphoxide is the key to the synthesis, and similar chemistry applied to (24) gave 3-deoxy-D-xylo-heptulosonic acid systems,23... 

Braverman and Grendi206 have shown that, depending on the type of substitution, allylic trichloromethanesulphenates undergo rearrangement to allylic trichloromethyl sulphoxides by one of two different pathways (equation 85). Rearrangement according to route a has been observed with allyl, crotyl and a, a-dimethylallyl sulphenates. It occurs... 

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... 

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 formation of rearranged products during nucleophilic substitution in a-bromo-ketones probably involves enolisation, followed by allylic (5n2 ) substitution. The ready conversion of4, 5i8-epoxy-3-ketones (45) into 2a-acetoxy-or 2a-hydroxy-4-en-3-ones is similarly rationalised.When the nucleophile is dimethyl sulphoxide, the resulting 2-oxysulphonium ion (46) breaks down with elimination of dimethyl sulphide to give the 4-ene-2,3-dione (47), or its A -enolic equivalent (48). 

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