Sulphenate Esters

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). 

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 latter anomalous" behaviour has been ascribed to the direct formation of pentacoordinated products from P(III) and the substrate as distinct from nucleophilic displacement by phosphorus so that the stability of the T.S. leading to the pentacoordinated molecule dictates the rate. >11 >LI There is no doubt that several reactions which display the anomalous rate sequence (eg with peroxides, sulphenate esters and dithietenes) do give pentacoordinated products and the proposal is given further support by the reaction of diethyl peroxide with a series of cyclic phosphines in which the rate sequence parallels the stability of the P(V) products.II Furthermore, under the appropriate conditions pentacoordinated products are also formed from alkenes (eqn. 2) and alkynesl . (eqn. 3) and although rate data is only available for... 

Although the fragmentation reactions of the molecular ions of sul-phones and sulphoxides varied, the first step in rationalizing their behaviour was initial isomerization to sulphinate (64) and sulphenate esters (65). A variety of reactions of this type has been collated by Fields and Meyerson (1968), who pointed out that isomerization of sulphoxides to sulphenate esters was a known thermal reaction (see also, Kutz and Weininger, 1968, Kinstle et al., 1968b). In experiments designed to compare the mass-spectral and thermal behaviour of a series of sulphoxides, it was observed that the thermal isomerization appeared to proceed, but no comparable behaviour was observed in the mass spectra (Entwistle et al., 1967). 

It has also been shown that reagents of type (45) in which the double bond is cis afford higher yields and greater stereoselectivity than the corresponding irons compounds [57], The cis (150) product prepared in this way could be isomerised to the required irons 15a product via a [2,3]sigmatropic rearrangement of a sulphenate ester to a 13-sulphoxide-14,15-m/ns-compound, and then treatment with trimethyl phosphite. 

Grignard reagents behave similarly,and a thioborane gives an un-symmetrical sulphide with a sulphenate ester. Tris(diethylamino)-phosphine converts cystine derivatives into corresponding lanthionines [NH2 CH(C02H) CH2]2S, 2 and the disulphide formed between penicillin sulphoxide and Bu SH (36 fine s in place of Me at S) forms the ethyl sulphide (36 Et in place of Me at S) by treatment with triethylphosphine. ... 

Sulphenate esters, prepared through an improved method involving JV-t-butylthio-phthalimide (148 = Bu ) and alkoxides, give quantitative... 

Alkyl chloromethyl ethers react with thiiran 1-oxide to give sulphenic esters (26), probably by way of an intermediate sulphoxonium salt (27). Thiiran oxide in FSOsH-SbF at — 78 C was protonated at sulphur and not at oxygen, according to n.m.r. studies. ... 

Aminoboranes react with sulphenic esters to give sulphenamides in good yield (Scheme 157). ... 

This behaviour is illustrated in a preparation of the 2-thioxopenam (258) from the sulphoxide (259). Thus, pyrolysis of (259) induces a sulphoxide-sulphenate ester rearrangement followed by intramolecular trapping to give the disulphide (260) which is converted in two steps into the penam (258). ... 

In contrast, the reverse of the sulphoxide-sulphenate ester rearrangement forms the basis for the synthesis of the dienes (261) and (262) and the enamine (263). The diene (261) is obtained via two consecutive 2,3-sigmatropic rearrangements when the butynediol (264 X = H) is treated with PhSCl-NEta, whereas diene (262) is formed after one 2,3-rearrangement from the mono-acetylated butynediol (264 X = Ac). When the same reagent combination is used with the propargyl alcohols (265) a similar 2,3-rearrangement occurs and... 

In interesting use of sulphenate esters In a general synthetic route to 2-deoxy-D-arablno-hexop,vranosyl disaccharides is illustrated in Scheme 10. The products illustrated were desulphurized,... 

The photochemical transformation of peri-fused thiopyran S-oxides (76) into related pyrans and ring-opened products probably involves sulphenate esters of type (77). ... 

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