Aliphatic sulfoxide

Gilbert and co workers42 found the same behavior of OH radicals with other aliphatic sulfoxides. In many of these cases the OH adduct is decomposed to the sulfonyl radical. 

ESR experiments employing in situ photolytic decomposition of the peroxydisulfate anion (S20g ) have been carried out to study the reaction of S04 with aliphatic sulfoxides. In the case of dimethyl sulfoxide three radicals are detected ( CHj, CH3 S02, CH2 S(0)CH3), the proportion being pH-dependent. The reaction is assumed to proceed via an initially formed radical cation (not detected) which would be rapidly hydrated to give an intermediate identical with that generated by OH addition on the sulfoxide. Such a process parallels the rapid hydration of radical cations formed from thiophene in their reactions with SO/ and... 

For the most pan, sulfoxides are crystalline, colorless substances, although the lower aliphatic sulfoxides melt at relatively low temperatures. The lower aliphatic sulfoxides are water soluble but as a class the sulfoxides are not soluble in water. They are soluble in dilute acids and a few are soluble in alkaline solution. DMSO is a colorless liquid selected properties are listed in Table 1. Dimethyl sulfoxide generally undergoes typical sulfoxide reactions. It is used herein as an illustrative example. 

Deoxygenation of suffoxideS to strides. Dichloroborane reduces aliphatic sulfoxides to sulfides almost quantitatively in a few minutes at 0° in I HF. Reduction of aryl sulfoxides is much slower (24 hr., 25°, excess BHClj) and yields arc lower. Ester,... 

Reports on the ability of microorganisms to selectively oxidize various types of sulfides to the corresponding chiral sulfoxides have grown significantly in the last few years (33). Chiral sulfoxides are evident in a variety of pharmaceutical and agricultural chemical compounds (33). The w hydroxylase from Pseudomonas oleovorans has been shown to produce a variety of chiral aliphatic sulfoxides from corresponding sulfides (34). Vinyl sulfox-... 

Aliphatic sulfoxides are not cathodically reducible, but some give a catalytic hydrogen wave in acid solution [240] at a lead cathode in alcoholic sulfuric acid diphenylsulfoxide [241] and dibenzylsulfoxide [242] have been reduced in fair yield to the sulfide. Methylphenylsulfoxide has been reduced in DMF or MeCN with phenol as proton donor at —2.3 V (SCE) to methylphenylsulfide [243]. 

Another 8-elimination to give an olefin observed by Schriesheim et al. is the base-catalyzed decomposition of aliphatic sulfoxides and sulfones. With potassium ( butoxide in DMSO the reaction proceeds easily at 55° ... 

In all oxidations of sulfides to sulfoxides, yield loss because of overoxidation to form the sulfones is common unless temperatures are low. Another source of yield loss in aliphatic sulfoxides with a-hydrogens arises from the Pummerer reactions, which occur at temperatures greater than 80° C under acidic conditions or in the presence of acid anhydrides/halides. The Pummerer reactions are quite general, leading to products of the general formula RSCR2Z, with Z being acetate, chloride, hydroxide, etc. 

Unlike the carbonyl, the unconjugated sulfoxide is not associated with a long wavelength absorption of its own. Therefore most of what is reported herein has to do with conjugated sulfoxides. Aliphatic sulfoxides are treated separately, though there are many commonalities with aromatic sulfoxide chemistry. The aliphatic compounds have been examined by gas phase physical chemistry mediods, which also justify a separate treatment. 

We begin with a brief discussion of the sulfoxide chromophore itself. It will be seen that, just as the sulfoxide bond does not lend itself to simple description, the chromophore is fairly well understood phenomenologically but not yet well described in the shorthand photochemists have developed for other functional groups. Sections III through VII constitute the bulk of the paper and develop the chemistry of conjugated sulfoxides by reaction type. The photochemistry of aliphatic sulfoxides is discussed in Section VIII, with emphasis on gas phase reactions. 

Another procedure for the deoxygenation calls for the use of phenyl phenylenedioxyphosphine (143). However, the mechanism presented by the authors does not explain the acceleration effect of iodine and the fact that aliphatic sulfoxides react faster than their aromatic counterparts. The alternative pathways below agree better with experimental observations. 

Hydrogen abstraction from sulflnic acids by alkoxy radicals represents another widely used approach to sulfonyl radicals [61]. This process is involved in sulfonyl radical production in course of hydroxyl radical scavenging by aliphatic sulfoxides [65] ... 

Mitchell C, Desai M, McCulla R, Jenks W, Armstrong D. Use of native and derivatized cyclodextrin chiral stationary phases for the enantioseparation of aromatic and aliphatic sulfoxides by high performance liquid chromatography. Chromatographia 2002 56 127-35. 

Sulfoxides and sulfides received some attention in the past few years especially with regard to their inhibition mechanisms. Thibault and Talbot examined aliphatic sulfoxides and found they form films that aid in the inhibition. Thiophene, a cyclic sulfide, can adsorb in Temkin fashion and bring about a significant reduction in the rate of H2 evolution. ... 

Katopodis AG, Smith HA, May SW. 1988. New oxyfunctionalization capabilities for om a-hydroxylases. Asymmetric aliphatic sulfoxidation and branched ether demethy-lation. JAm Chem Soc 110 897-899. 

Across S=0 bonds Sulfoxides react with A-sulfinylsulfonamides to give sulfilimine derivatives 23 and sulfur dioxide. The aliphatic sulfoxides react at room temperature, while heating at 80-100 °C is required for aromatic sulfoxides... 

The reaction is fast and results in a mixture of isomeric sulfoxides in the ratio 2,0 (( ), This observation is in analogy with that of Mislow who studied this isomerization for a number of aliphatic sulfoxides and proposed the mechanism which includes formation of an intermediate with the structure of sulfur dichloride type. 

---