Alkyl phenyl sulfones

The oxidative dimerization of the anion of methyl phenyl sulfone (from a Grignard reagent) in ethereal solution in the presence of cupric chloride in 5% yield has been reported47. Despite the reported48 poor stability of the a-sulfonyl C-centered radicals, Julia and coworkers49 provoked the dimerization (in 13 to 56% yields) of the lithiated carbanion of alkyl phenyl sulfones using cupric salts as oxidants. The best results are obtained with cupric triflates in THF-isobutyronitrile medium (56% yield for R = H). For allyl phenyl sulfones the coupling in the 3-3 mode is predominant. 

Hydroxy- bzw. 2-Alkoxy-alkyl)-phenyl-sulfone konnen in DMF in Gegenwart von Essigsaure Oder Phenol als Protonendonator an Quecksilber kathodisch an der S-CAlkyl-Bindung unter Bildung von Olefinen (bis 90% d. Th.) gespalten werden. Mit zunehmender Protonendonator-Konzentration nimmt der Anteil des Alkans zu (bis zu 40% d.Th.) ... 

Acyclic alkyl phenyl sulfones undergo an alkyl-sulfur bond cleavage [123] however, in cyclic arylsulfones the aryl-sulfur... 

Gin utilised the reduction of an alkyl phenyl sulfone in a synthesis of the anti-leukaemia natural product (-)-deoxyharringtonine 61 Treatment of complex sulfone 61 with SmI2-HMPA gave 62 in 74% yield (Scheme 4.51). 

Oxidative desulfonylation. The a-anion of alkyl phenyl sulfones on reaction with 1 is converted into aldehydes or ketones in good to high yield (equation I). 

In 1973 Marc Juba and J.M. Paris [86] developed an olefination protocol involving three distinctive steps (Scheme 63) (1) reaction of an anion generated from alkyl phenyl sulfone 215 and n-butyllithium with an aldehyde to provide the adduct 216 (2) acetylation (or benzoylation) of 216 and (3) sodium amalgam reductive elimination of suhbnyl-ester 217. 

The a-methyltoluene-2,a-sultam auxiliary is also displaced by a variety of dilithiated alkyl phenyl sulfones. This unique procedure provides direct access to synthetically useful p-oxo sul-fones which may be further functionalized or simply subjected to reductive desulfonation to give alkyl ketones. A particularly strik-... 

The Julia olefination reaction is highly regioselective and ( )-stereoselective, providing a valuable alternative to the Schlosser reaction for making rrans -disubstituted olefins. The reaction involves condensation of a metalated alkyl phenyl sulfone with an aldehyde to yield a P-hydroxysulfone, which is then subjected to a reductive elimination to produce the alkene. There are limitations to the preparation of tri- and tetra-substituted alkenes via the sulfone route because the P-alkoxy sulfones derived from addition of the sulfone anion to ketones may be difficult to trap and isolate or they may revert back to their ketone and sulfone precursors. 

The alkyl phenyl sulfone precursors for the olefination may be prepared by the reaction of alkyl halides with sodium benzenethiolate, followed by oxidation of the alkyl phenyl sulfides formed with mCPBA. Alternatively, displacement of an alkyl bromide or iodide with the less nucleophilic sodium benzenesulfmate PhS02Na leads directly to the alkyl phenyl sulfone. 

Alkyl phenyl sulfones (piCj,27) are nearly as acidic as esters hence they are readily deprotonated by n-BuLi, LDA in THF, or EtMgBr in THF to give a-metalated sulfones. Their reaction with aldehydes gives a mixture of diastereomeric P-phenylsul-fone alkoxide adducts. Reductive elimination of the benzenesulfinate moiety from the adduct to produce the alkene is usually slow. To minimize side reactions, the hydroxyl group is first converted to an acetate, benzoate, mesylate, or /7-toluenesul-fonate and then treated with an excess of sodium amalgam [Na(Hg), prepared by adding small pieces of sodium to mercury] in methanol to furnish the trans-dlk n P... 

Tri-n-butyltin hydride is unproductive in the reduction of non-activated alkyl phenyl sulfones. Thus, the selective desulfonylation of a p-kcto phenyl sulfone in the presence of an alkyl sulfone is possible. Another interesting example of chemoselectivity is seen in the reduction of a-arylsulfonyl phosphonates.176 Tin hydride reduction of this kind of non-activated sulfone produces C-P fragmentation to afford the corresponding sulfone derivatives (Eq. 106a). In contrast, it... 

Reductive desulfonylation. Alkyl phenyl sulfones are cleaved unidirection-ally, alkyllithium thus generated can be utilized accordingly. 

The a-methyltoluene-2,o -sultam auxiliary is also displaced by a variety of dilithiated alkyl phenyl sulfones. This unique procedure provides direct access to synthetically useful fi-o o sul-fones which may he further functionalized or simply subjected to reductive desulfonation to give alkyl ketones. A particularly striking use of this method is the preparation of p-oxo sulfone 8, a key intermediate in a concise synthesis of (—)-semicorole (eq 5). Remarkably, the MeCLi2S02Ph reagent attacks selectively the C(4)-imide C=0 group in preference to the C(6)-ester C=0 group and no epimerization occurs at C(3) or C(F). 

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