Sulphenates allyl

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. 

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). 

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 sulphenates, rearrangement of 720-736 Allylsulphenic acids 747 Allyl sulphinates, rearrangement of 670-676 Allylsulphinyipyrazolenines, photolysis of 749... 

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. 

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. 

A new and versatile method for the generation of radicals has been developed, based on the photolysis of alkyl 4-nitrobenzene-sulphenates the tertiary alkoxide radicals (97), formed on irradiation of the sulphenates (98), undergo /3-scission to afford the ethyl aryl sulphides (99) by the pathway outlined in Scheme 5. This approach should prove useful in the preparation of substituted allyl radicals. A mild and selective photosensitised hydrolysis of p-toluenesulphonyl esters has been described, using either 1,5-... 

Reactions.—Full details are now available" of the photochemical and thermal [1,3] phenylthio shifts of allyl phenyl sulphides [(73)- (74)]. Oxidation of such sulphides can lead to allyl alcohols through the known sulphoxide-sulphenate equilibrium with sulphenate trapping. 

Continuation of studies aimed at preparing sulphenes by pyrolysis of sulphonyl derivatives has involved the allyl vinyl sulphone (134), which on heating at 170 °C in the liquid phase, or at 800 °C in the gas phase, gives products derived from the sulphene, itself arising through a sulpho-Cope [3,3]sigmatropic rearrangement. ... 

Allylic sulphenic acids are transient intermediates in the rearrangement of episulphoxides carrying a suitably located H atom /ru/i5-but-2-ene episulphoxide gives diallyl thiolsulphinate via HaC=CH CHMeSOH, the product (145) existing in equilibrium with the butenyl thio-sulphoxylate (146). 

The phenyl analogue likewise gave a high yield of benzoylethylene. Along the same line, King and Harding have reported a sulpho-Cope rearrangement which appears to involve sulphene formation. Vinyl allyl sulphone, when heated to 170 °C in the liquid phase or to 800 °C in the gas phase, probably was converted into the sulphene (87). In the gas phase, pent-4-enal was isolated, whereas in the liquid phase addition of phenol led to a phenyl sulphonate. 

Uses of Saturated Sulphides, Selenides, and Tellurldes in Synthesis.— These applications are mostly based on the C—C bond-forming reactions of sulphenyl carbanions the extensive uses of vinyl sulphides and their allyl and propargyl analogues are discussed in a later section. Some methods for C—S or C—Se bond cleavage, which are used to terminate a use in synthesis, have been discussed in an earlier section other methods, notably the conversion of the sulphide into a sulphoxide followed by pyrolytic elimination of the sulphenic acid, are covered in later sections. 

The 5>>n-elimination of sulphenic and selenenic acids from unsaturated sulphoxides and selenoxides introduces a further site of unsaturation, examples being the addition of allyl alcohols to allenic sulphoxides to give ff-(allyloxy)vinyl sulphoxides... 

Allyl sulphenates show promise as hydroxyl protecting groups. These are stable under conditions in which many types of groups are cleaved and may themselves be removed by Pd (O)-calalysed transfer (see Chapter 7). ... 

The addition products of [l,3-bis(phenylseleno)allyl]lithium and electrophiles may be converted, in high yields, into unsaturated aldehydes, this now being the subject of a full paper. The versatile sulphoxide-sulphenate rearrangement provides the regio- and stereo-control in a route to -substituted ( )-l-aryl-enones (Scheme 30). -Substituted enones may also arise from alkylation of... 

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