Allyl sulphones reactions

Subsequently, Julia, Uguen and Callipolitis104 105 used both lithium metal in ethyl-amine and sodium amalgam in ethanol to effect reductive cleavages of j8-hydroxysulphones or of allylic sulphones. The latter reaction is part of a synthetic sequence for the construction of alkenes that has been used with some considerable success... 

As an alternative to radical chlorination, use has been made of carbon tetrachloride and hexachloroethane in the presence of a quaternary ammonium salt, as source of the chloronium ion for reaction with activated alkylbenzenes [38], Benzyl chlorides need the additional activation of a nitro group for their conversion into the corresponding nitrobenzotrichlorides, whereas benzal chlorides do not need the extra activation for a similar conversion. The same synthetic protocol, using hexachloroethane, has been used for the conversion of allylic sulphones into the 1,1-dichloro derivatives [39],... 

The reaction of methylenesulphones with allyl halides in the presence of quaternary ammonium salts produces the 1-allyl derivatives [52], unlike the corresponding reaction in the absence of the catalyst in which the SN- product is formed (Scheme 6.5). In contrast, alkylation of resonance stabilized anions derived from allyl sulphones produces complex mixtures [51] (Scheme 6.6). Encumbered allyl sulphones (e.g. 2-methylprop-2-enyl sulphones) tend to give the normal monoalkyl-ated products. Methylene groups, which are activated by two benzenesulphonyl substituents, are readily monoalkylated hydride reduction leads to the dithioacetal and subsequent hydrolysis affords the aldehyde [61]. 

As reactions 68 and 69 above exemplify, the substitution of the allylsilane usually takes place with an allylic shift (Se2 ). This can be synthetically useful, for example in the isomerization of allyl sulphones 123 to vinyl sulphones 124 (equation 74)145. The reaction is also highly stereospecific (>90% E) (vide infra). 

A few instances have been noted of allyhc compounds bearing an electron-attracting substituent undergoing addition reactions with amines. These cases appear to involve shift of the double bond from the 8,y- to the a, 8-position prior to reaction. For example, benzyl allyl sulphone and piperidine react to give benzyl 8-piperidinopropyl sulphone (reaction 81)i i. Allyl cyanide similarly reacts with am-... 

On treatment with cyanide ion, vinyl sulphones are converted into a,/3-unsaturated nitriles in which the direction of olefin polarization has been reversed, e.g. (105) - (106). Allylic sulphones are also suitable starting materials since they can be equilibrated with vinyl sulphones by adding potassium t-butoxide to the reaction mixture. With magnesium as counter-ion, the triphenylsilylacetonitrile anion undergoes stereoselective Peterson olefination... 

Allylic sulphones are available through the reaction of a t-butyl sulphoxide and an allyl alcohol with A -chlorosucdnimide, and through the reaction of an allyl alcohol with di(AT-phthalimido) sulphide or di(iV-imidazolyl) sulphide to give a sulphoxylate, e.g. CHa=CHCH20S0CH2CH=CH2, which rearranges to the bis(allyl) sulphone by way of the sulphinate. Further study of the rearrangement of iV-aryl arenesulphonamides to iV-(u-aminoaryl) aryl sulphones has been described. ... 

Michael addition reactions of allyl sulphones and a/3-unsaturated carbonyl compounds provide useful starting points in synthesis, illustrated in a synthesis of chrysanthemate ester [Me2C=CHCH2S02ph -I- Me2C=CHC02R -> MeaC= CHCH(S02Ph)CMe2CH2C02R cis- and tm/is-cyclopropane esters]. ... 

Otera and coworkers developed an alternative procedure to the Julia method for generating dienes or alkynes in the same reaction by the double elimination of /J-acetoxy or /1-alkoxy sulphones with potassium /-butoxide (equation 58)98,99. The reaction pathway leading to the diene or an alkyne depends on the substrate structure and the reaction conditions. If an allylic hydrogen is present in the substrate then diene is formed, otherwise, the alkyne is the product of the reaction. This modified Julia methodology has een applied to the synthesis of vitamin A (equation 59)100, alkaloids piperine (equation and trichonine (equation 61)102. 

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