Sulphonyl group

NaOCHjCHa. White solid (Na in EtOH). Decomposed by water, gives ethers with alkyl halides reacts with esters. Used in organic syntheses particularly as a base to remove protons adjacent to carbonyl or sulphonyl groups to give resonance-stabilized anions. 

Intramolecular hydrogen bonds between sulphinyl or sulphonyl groups and hydroxyl groups have also been described106,107. The IR shifts Vjq in these experiments were found at around 1005-1010cm 1108 U0. Several other papers which describe hydrogen bonds of sulphoxides and sulphones are given in References 111-120. 

Solanesol and other prenyl alcohols are important as metabolites in mulberry and tobacco leaves and in the synthesis of isoprenoid quinones. Hence, Sato and collaborators107 have developed a stereoselective synthesis of all-trans-polyprenol alcohols up to C50. Construction of the requisite skeletons was accomplished by the alkylation of a p-toluenesulphonyl-stabilized carbanion, followed by reductive desulphonylation of the resulting allylic sulphonyl group. This was achieved most efficiently by the use of a large excess of lithium metal in ethylamine (equation (43)), although all reaction conditions led to mixtures. The minor product results from double bond rearrangement. 

Julia and Paris120 described an olefin synthesis, based on the use of a sulphonyl group which directs the formation of a carbon-carbon bond. Subsequent reductive elimination with sodium amalgam leads to the alkene, as outlined in equation (50). The reaction sequence is similar in principle to an olefin synthesis first developed by Cornforth121. The yields of all steps are generally above 80%. 

A second paper161 describes the use of the same base in either THF or t-butanol for the elimination of a-acetoxy phenyl sulphones as outlined in equation (68), in essence a reaction sequence very similar to the Julia olefin synthesis (Section III.B.3) except in the method by which the sulphonyl group is finally removed. 

Perhaps of more significance is a detailed study132 into the reductive desulphonylation of 7-methyl-7-phenylsulphonylestratrienes. The goal was stereoselective removal of the sulphonyl group, and hydride reductions, alkali-metal-amalgam reductions and electrochemical reductions were explored. The latter proved to be the most effective and the best results are illustrated in Scheme 3. 

B. Cathodic Activation of Unsaturated Systems by Sulphonyl Groups. . 1019... 

The sulphonyl group involved in cathodic and anionic eliminations. 1036... 

The sulphonyl group as activating factor in SRN1 reactions. 1039... 

Eliminations can be promoted by arene sulphonyl groups simultaneously acting as electroactivated systems leaving groups and strongly withdrawing moieties. 

Quite similarly, y-ketosulphones may give elimination in aprotic solution48. A multisweep voltammetric experiment (Figure 11) shows the formation, already from the second sweep, of the activated olefine. Here, the sulphonyl group leaves ... 

As in the case of enolates and organic anions in general65 it may be expected that the oxidation of —C—H systems strongly activated by sulphonyl groups in basic solvents may produce C—C dimer bonds. A very recent66 first example concerns the oxidation of... 

Electrophilic aromatic substitution, influence of sulphinyl and sulphonyl groups on 532, 533... 

Free radicals, stabilization by sulphinyl and sulphonyl groups 533-535 Furans 638, 679, 840... 

An alternative 2+2 route to 3-lactams is to use ketene-like (23) on alkenes and reduce away the sulphonyl group. 

Since sulphones 204 are easily available compounds one would expect that they could be used as starting materials for the preparation of sulphoxides via the selective removal of one oxygen atom from the sulphonyl group (equation 112). Up to now, there is only one example reported of a direct reduction of a sulphone to a sulphoxide. The bicyclic dideuterio sulphone 205 after 24 h treatment with three-fold excess of diisobutyl aluminium hydride in boiling dichloromethane gave the corresponding sulphoxide 206 in 36% yield (equation 113). A two-step procedure for the selective reduction of sulphones to sulphoxides, which involves an initial reaction of sulphone 204 with aryldiazonium tetrafluoroborate 207 to form aryloxysulphoxonium salt 208 and its subsequent reduction (equation 114), was alluded to by Shimagaki and coworkers and... 

Despite the aversion of the sulphonyl group to function as a nucleophile, there are a limited number of literature reports that deseribe sueh a process . The first of these does not lead to a reduetion at sulphur and is thus not direetly relevant, but the report by Braverman and Duar deseribes reaetions in whieh an acetylenie sulphinate ester ean undergo a [2,3] sigmatropie rearrangement to an allenie t-butyl sulphone. Reaetion of this sulphone with the appropriate eleetrophile, for example bromine, gave a y-sultine, formation of whieh requires the partieipation of the sulphonyl group in an intramoleeular cyclization process. The reactions are outlined in equation (40). 

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