Allylic sulfone

Allylic sulfones undergo Pd-catalyzed elimination. The synthesis of an a,ft-unsaturated ketone by the elimination of the allylic sulfone group in 503 is an examplc[339]. 

Various terminal allylic compounds are converted into l-alkenes at room temperature[362]. Regioselective hydrogenolysis with formate is used for the formation of an exo-methylene group from cyclic allylic compounds by the formal anti thermodynamic isomerization of internal double bonds to the exocyclic position[380]. Selective conversion of myrtenyl formate (579) into /9-pinene is an example. The allylic sulfone 580 and the allylic nitro compound... 

Desulfonylation of equally substituted allylic sulfones with NaBH4 and LiBHEt3 usually yields a mixture of regioisomeric alkenes[406,407]. However, the regioselective attack of the less substituted side of the unsymme-trically substituted allylic system with LiEtjBH has been utilized for the removal of the allylic sulfone group in synthesis of the polyprenoid 658[408],... 

The following compounds have been obtained from thiete 1,1-dioxide Substituted cycloheptatrienes, benzyl o-toluenethiosulfinate, pyrazoles, - naphthothiete 1,1-dioxides, and 3-subst1tuted thietane 1,1-dioxides.It is a dienophile in Diels-Alder reactions and undergoes cycloadditions with enamines, dienamines, and ynamines. Thiete 1,1-dioxide is a source of the novel intermediate, vinylsulfene (CH2=CHCH=SQ2). which undergoes cyclo-additions to strained olefinic double bonds, reacts with phenol to give allyl sulfonate derivatives or cyclizes unimolecularly to give an unsaturated sultene. - Platinum and iron complexes of thiete 1,1-dioxide have been reported. 

Stable enolates such as diethyl malonate anions react with allyl sulfones (or acetates) in the presence of nickel complexes to give a mixture of the a- and /-product83. The regioselectivity is generally poor in the nickel-catalyzed reaction, but the molybdenum-catalyzed reaction is selective for alkylation at the more substituted allylic site, thereby creating a quaternary carbon center84. 

Allyl sulfonates (35, 36) show analogous behavior. Transfer constants are reported in Tabic 6.8. Other compounds with weak A-R bonds cf. 11) that have the capacity to act as transfer agents are listed in fable 6,9. Allyl bromides 43a, 44, and 45a give predominantly chain transfer whereas, the chlorides (e.g. 45b)... 

Allyl sulfones formed from allyl sulfinates (cf. equation 1) can easily tautomerize to give a, /J-unsaturated sulfones26 in cases for which R1, R2 are part of an (hetero) aromatic system, this tautomerization occurs spontaneously. Similarly, sulfinic acid esters from jV-phenylhydroxamic acids as reactive intermediates rearrange to give o-(major part) and p-sulfonylanilines (minor part)27 ... 

In allyl sulfones 1,3-migrations of the sulfonyl group take place thermally49 51 or Pd(0)-catalyzed52 (equation 11). 

Allylic sulfones and a, /5-unsaturated sulfones are known to be in equilibrium314-319. Allylic sulfones, such as 242, isomerize to a, /5-unsaturated sulfones 243 upon treatment with a catalytic amount of potassium t-butoxide in dry THF. The a, /5-unsaturated sulfones can be converted to the corresponding olefins upon desulfonation with sodium amalgam320 or aluminium amalgam294,321. Since treatment of allylic sulfones with potassium-graphite gives 2-alkenes, alkylation of allylic sulfones and subsequent desulfonation is a useful process for the synthesis of olefins, as shown in Scheme 6. 

Koncienski295 reported a new synthesis of allylic alcohols starting from the allylic sulfones via formation of epoxysulfones. 

Carbanions derived from allylic sulfones 309 reacted with cyclohexenone, giving mainly... 

The Ramberg-Backlund reaction has been utilized for the preparation of polyenes. 1,3-Butadienyl allyl sulfones 398 and 399 were transformed into the tri- and tetra-enes 400 and 401 by alkylcuprate addition and the Ramberg-Backlund-type S02 extrusion449. Julia and coworkers450 carried out the Michael addition of various nucleophiles such as ethanol, t-butyl acetoacetate and phenyl thioacetone to allyl dienyl sulfones 402 and then converted them to diallyl sulfones 403. The sulfones were transformed into isoprenoid, 404 by the Ramberg-Backlund reaction. 

TABLE 1. Reaction of allyl sulfones 1 with n-hexylmagnesium halides (n-HexMgX)4... 

Trost and coworkers7 have reported the use of palladium(O) as a catalyst for displacement of the phenylsulfonyl group by soft nucleophiles. Thus, treatment of allyl sulfone 12 with the sodium salt of dimethyl malonate in the presence of 5 mol % of... 

TABLE 2. Product distribution for the displacement reaction of allyl sulfones 9 with lithium dialkyl cuprates6... 

For trisubstituted olefins, the nucleophile attacks predominantly at the less substituted end of the allyl moiety, e.g. to afford a 78 22 mixture of 13 and 14 (equation 7). Both the oxidative addition of palladium(O) and the subsequent nucleophilic attack occur with inversion of configuration to give the product of net retention7. The synthesis of the sex pheromone 15 of the Monarch butterfly has been accomplished by using bis[bis(l,2-diphenylphosphinoethane)]palladium as a catalyst as outlined in equation 87. A substitution of an allyl sulfone 16 by a stabilized carbon nucleophile, such as an alkynyl or vinyl system, proceeds regioselectively in the presence of a Lewis acid (equation 9)8. The... 

Trost and Ghadiri19 have found a Lewis-acid-mediated intramolecular cyclization of allyl sulfones. When the allyl sulfone 40 is treated with A1C13, polycondensed aromatic system 41 can be obtained in good yield (equation 24). The mechanism probably involves... 

Desulfurization of fl, a-epoxy sulfones 239 prepared from allylic sulfones 238 and m-chloroperbenzoic acid with sodium amalgam leads to the formation of allyl alcohols (240) in good yields (equation 144)138. Allyl alcohols prepared by this method are listed in Table 16. 

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