Allylic sulfenylation reactions

Sigmatropic rearrangements of anions of (V-allyl amines have also been observed and are known as aza-Wittig rearrangements.291 The reaction requires anion stabilizing substituents and is favored by (V-benzyl and by silyl or sulfenyl substituents... 

Hydrolysis of perfluoro-3-isopropyl-4-methylpentenyl-2-sulfenyl chloride 34 having a mobile allyl fluorine atom ends with the formation of perfluoro-2,4,4-trimethyl-3-isopropylthiete 35 (yield 30%) (89IZV1380). The reaction occurs via the intermediate formation of the derivative of sulfenic acid 36 due to the high mobility of the allylic fluorine atom. 

Alkynyl sulfenylotion.x Reaction of a lithium acetylide with the adduct (a) of the reagent (1) with an alkene results in a complex mixture or an allylic sulfide. However, alkynyl sulfenylation can be effected with the ate complexes of a lithium acetylide with a thiophile. Two complexes can be used the 2 1 complex with (C2H5)2A1C1 or the 1 1 complex with A1(C2H5)3. 

Finally, in order to directly incorporate the nitrogen and sulphur functionalities in a single step with total stereoselectivity, the chiral allylic trichloroacetimidate 16 was treated with methyl sulfenyl triflate to give the corresponding A -sulfenyl imidate 17 in good yield. Further reaction of 17 with methyl sulfenyl triflate gave the 4,5-dihydro-l,3-oxazole 18, together with a minor amount of the trichloroacetamide 19, formed by hydrolysis of 18246. 

The reaction of a-sulfenylated allylic carbanions with electrophiles may give both the a- and y-prod-ucts (equation 7). Regiochemical control of this ambident anion is dependent upon many factors, including substituents, counterions, the solvent system, the type of electrophile and steric effects. 

The scope of cyclodestannylation as a method for the synthesis of cyclopropyl compounds appears to be limited. Whereas tributyl(norborn-2-en-5-yl)tin gives the nortricyclic sulfide 12 in 75% yield, bromination of tributyl(cylohex-3-en-yl)tin at — 65°C does not lead to the anticipated 2-bromobicyclo[3.1.0]hexane. Unexpectedly, the cyclodestannylation of tributyl(3-methyl-2-enyl)tin with a sulfenyl chloride also fails, although a Markovnikov addition to the double bond would have formed a tertiary carbenium ion y to tin. Instead an SE2 reaction results to give an allylic sulfide. Addition of 3-chloroperoxybenzoic acid to but-3-enyltin does not lead to any cyclodestannylation. Instead, the corresponding tributyl(3,4-epoxybutyl)tin is obtained in 78% yield. This epoxide readily undergoes a 1,3-elimination reaction to cyclo-propylmethanol using both Lewis and protic acids.13... 

Rearrangement of Thioacetals to Aldehydes. Sato et al. reported the rearrangement of a-hydroxy thioacetals to a-sulfenyl aldehydes (eq 34). The thioacetals are prepared by the addition of the anion of methoxy(phenylthio)methane to aldehydes and ketones. This reaction is general for alkyl, allyl, and aromatic carbonyl compounds. 

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