Allylic sulfenylation

Sulfenyl chlondes react with allyl alcohols to yield allyl sulfenates, whtch are in equihbnum with the allyl sulfoxides [12] (equation 9a) These products can be oxidized to the corresponding sulfones (equation 9b) Pyrolysis of the sulfoxides gives sulfines or evidence for the presence of sulfmes Pyrolysis of sulfones leads to unsamrated compounds by extrusion of sulfur dioxide [12] (equation 9c)... 

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... 

Direct transformation of thiazoline-azetidinones 2 into 3 -thio-substituted cephalosporins 6 has been performed by ring opening of the thiazoline moiety with sulfenyl chloride followed by ring closure with ammonia in dimethylformamide and simultaneous displacement of the allylic chlorine atom with the leaving thiolates. 

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. 

When t7. -l-(2,5-dichlorophenyl)-4-methyl-2-cyclohexenol is treated with 2,4-dinitrobenzene-sulfenyl chloride in the presence of triethylamine. the allylic sulfoxide 9 is stereoselectively formed via [2,3] sigmatropic rearrangement of the initially formed sulfenate ester 8106. 

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. 

Treatment of a number of substituted allylic alcohols 102 with morpholino sulfenyl chloride 103 at low temperature led to the formation of amidosulfoxy-lates 104, which rearranged readily during warm up to room temperature. In accordance with the proposed transition-state structures for [2,3]-sigmatropic rearrangements [6,40], the double bond geometry in 105 was found to be E for all cases with = H, CH3 (with a decreased selectivity for some functionalized... 

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. 

Certain sulfoxides can be prepared by rearrangement of the sulfenate esters thus, allyl arenesulfenate esters (7), obtained by condensation of the sulfenyl chloride with allyl alcohol (8), spontaneously rearrange to the allyl sulfoxides (9) (Scheme 6). The rearrangement also occurs with alkynic alcohols for instance, trichloromethanesulfenyl chloride (10) reacts with propargyl alcohol (11) to form the allenic sulfoxide (12) (Scheme 7). 

The formation of sulfenyl carbanions is facilitated when the substrate contains a suitably positioned second sulfur atom or double bond, as in the case of dithians (see Chapter 3, p. 31) or allyl sulfides (46). The latter are thus easily converted into carbanions which can then be alkylated, and this provides a convenient procedure for coupling allyl groups for example, the allyl sulfide (46) can be transformed into diallyl (47) (Scheme 23). 

Cyclizations. A route to substituted naphthalenes by intramolecular cyclization involves attack by a nascent allyl anion to a ketone group. On the other hand, the generation of N-arylindolines from arylamines and o-halostyrenes is a more complex process. Arylamines. The Pd-catalyzed arylation of amines depends critically on l-BuOK. Synthesis of sulfur compounds. a-Sulfenylation under mild conditions is realized... 

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