Reduction of sulfonates

Also, the reduction of sulfones 17 to the sulfoxides 16 would seem to be the method of choice for the preparation of the latter, provided the former are readily available. 

Kudlich M, Hetheridge MJ, Knackmuss HJ, Stolz A (1999) Autoxidation reactions of different aromatic o-aminohydroxynaphthalenes that are formed during the anaerobic reduction of sulfonated azo dyes. Env Sci Technol 33 869-901... 

Mechsner K, Wuhrmann K (1982) Cell permeability as a rate limiting factor in the microbial reduction of sulfonated azo dyes. Eur J Appl Microbiol Biotechnol 15(2) 123-126... 

A different electrochemical approach was applied to the cathodic reduction of sulfones in W,JV-dimethylformamide (Djeghidjegh et al., 1988), for example t-butyl phenyl sulfone, which is reduced at a more negative potential ( pc = -2.5 V) than is PBN (-2.4 V). Thus, the electrolysis of a mixture of PBN and the sulfone would possibly proceed via both true and inverted spin trapping. If a mediator of lower redox potential, such as anthracene (-2.0 V), was added and the electrolysis carried out at this potential, it was claimed that only the sulfone was reduced by anthracene - with formation of t-butyl radical and thus true spin trapping was observed. It is difficult to see how this can be reconciled with the Marcus theory, which predicts that anthracene - should react preferentially with PBN. The ratio of ET to PBN over sulfone is calculated to be 20 from equations (20) and (21), if both reactions are assumed to have the same A of 20 kcal mol-1. 

The reduction of sulfone to either sulfoxide or sulfide (i.e., disulfoton) was not observed under the same conditions. Since the bacterial populations in sediments and soils are higher than in typical surface waters (Mossman et al. 1988), biodegradation is expected to play a major role in the loss of disulfoton in soil and sediment, as occurred in the disulfoton spill in the Rhine River (Capel et al. 

Reduction of sulfones to sulfides has been accomplished by lithium aluminum hydride [687], diisobutyl aluminum hydride [659] and sometimes by zinc dust in acetic acid [657]. Diisobutyl aliuninum hydride (Dibal-H) was found to be superior to both lithium alumimun hydride and zinc. At least 2.2 mol of the hydride were necessary for the reduction carried out in mineral oil at room... 

Reduction of sulfonic odds to disulfides. This combination of reagents reduces aryl sulfonyl halides and sulfonic acids to disulfides in yields generally >90%. 

Reduction of sulfonic acids. P4S,o in sulfolane reduces sulfonic acids (and sulfinic acids) directly to polysulfides in good yield. The products are reduced to thiols by LiAlH4 or NaBH4 (equation 1). 

In analogy to the reduction of aliphatic halogen compounds, the reduction of sulfonates can be used for the alkylation of phenylacetic acids 435) ... 

The reduction of sulfones with Sml2 can result in deoxygenation, to give the parent sulfide,59 or carbon-sulfur bond cleavage, depending on the substrate and the reaction conditions employed.60 For example, alkyl and alkenyl phenyl sulfones are reductively cleaved by Sml2 in the presence of HMPA. In the reduction of alkenyl sulfones, competing reduction of the electron-deficient alkene is not observed (Scheme 4.50).60... 

Reduction of Sulfonic and Sulfmic Acids and Their Derivatives... 

Radivoy, G., Alonso, F., Yus, M. The NiCl2.2H20-Li-arene (cat.) combination as reducing system 5. Reduction of sulfonates and aromatic compounds with the NiCl2.2H20-Li-arene (cat.) combination. Tetrahedron 1999, 55,14479-14490. 

Cyclobutenes prepared by the Ramberg-BScklund reaction are almost always unsubstituted at the vinylic positions. In 1974, Paquette introduced a related and complementary ring contraction which is particularly suitable for the synthesis of 1,2-dialkylcyclobutenes. The reaction takes place when carbanions of five-membered cyclic sulfones are treated with LAH in refluxing dioxane (Scheme 19). The mechanism of the reaction is not clear. Good yields are obtained only when the sulfone is 2,5-dial-kylated in the absence of these groups, simple reduction of sulfone to sulfide becomes a serious side reaction. Dibenzyl sulfone is converted into a mixture of stereoisomeric stilbenes (56%) and dibenzyl sulfide (23%) under the same conditions. ... 

On the other hand, carbonyl reduction is observed in reduction of sulfone derivatives bearing dialkyl ketone moieties with Na/Hg if very long reaction times and room temperature are employed (Eq. 82),39 This reduction141 as well as other side-reactions such as pinacol couplings142 are also observed with substrates bearing aromatic ketones even when low temperature conditions and short reaction times are used (Eq. 83). 

B), whereas the reduction of sulfones has never been found to occur. 

Aluminum amalgam (Al/Hg) is also a useful reagent that is most commonly employed for hydrogenolysis of sulfur compounds.533 Reduction of sulfoxides is an important application,534 as is reduction of sulfones. Aluminum amalgam reduces the a-phenylsulfonyl moiety in 554 to give lactone 555 in 68% yield.535 Aluminum amalgam has also been used for reduction of nitro compounds to the amine,536 and reduction of azides to the amine.532... 

Other reductions involve sulfur (Fig. 31.25) and a few other atoms. Thus, disulfides are reduced to thiols, and there are numerous examples of the reduction of sulfoxides. In contrast, the reduction of sulfones has never been found to occur. 

---