Sulfur-Containing Nucleophiles

Plummer invented a process for the biodesulfurization of hydrocarbons [157], in which organic sulfur compounds contained in liquid hydrocarbons are converted to elemental sulfur. The reaction is carried out in the presence of a biocatalyst and hydrogen, by dissolving completely the liquid hydrocarbons in an organic solvent, such as a nucleophilic and/or electrophilic solvent(s). The nucleophilic solvent should have a pKa greater than 2, and the electrophilic solvent more negative than -2. Recommended nucleophilic solvents include -butylamine, diethylamine, butanediamine, ethylenimine, toluene, pyridine, aniline, and acetophenone. The electrophilic solvents could be methylethylketone, pyrrole, or benzaldehyde. 

Concerning the M=Co, bond, most of the reported examples result from inter- or intramolecular additions of anionic nucleophiles containing at least two reactive heteroatoms. Thus, sodium dimethyldithiocarbamate was found to react with the cationic allenylidene [RuTp(=C=C=CPh2)(PPh3)2] [PFg] (76) to generate the alle-nyl-metallacycle 77 (Scheme 26) as the result of the nucleophilic addition of one of the sulfur atoms at the Cq, carbon and subsequent coordination of the second sulfur to the ruthenium center, with concomitant release of a triphenylphosphine ligand [282]. Complex 77 could also be synthesized by treatment of the neutral derivative... 

Thietanone (53) (79LA1768) and thietane (54) (72BAU505) react with sulfur-containing nucleophiles giving ring-opened products. It is thought that these reactions are initiated by nucleophilic attack by the sulfur nucleophile on the ring sulfur. 

APS is reduced (Eq. 18-32, step b) by APS reductase, a 220-kDa iron-sulfur protein containing FAD and several Fe-S clusters. An intermediate in the reaction may be the adduct of sulfite with FAD, which may be formed as in Eq. 18-32. The initial step in this hypothetical mechanism is displacement on sulfur by a strong nucleophile generated by transfer of electrons from reduced ferredoxin to cytochrome c3 to the flavin.364... 

In different types of condensed polycyclic systems, mostly nitrogen-containing systems, the elimination of attached fluorine by thiols has proved a valuable synthetic tool for the introduction of sulfur moieties. In 4-(aminosulfonyI)-7-fluoro-2,l,3-benzoxadiazole(l) the reactivity of the fluorine towards sulfur nucleophiles is sufficiently high that it can be used analytically for the detection of thiols14 (c.g., in peptides). The reaction proceeds almost quantitatively. 

Among the various sulfur nucleophiles which are encountered in natural waters, most are Bronsted acids or bases, i.e., they can accept or lose a proton. The sulfhydryl functional group is a monoprotic Bronsted acid, while H2S and H2SO3 are diprotic Bronsted acids. The rate of displacement of halide from a given substrate in aqueous solution containing a nucleophilic Bronsted acid depends upon the relative concentrations among the different protonated forms of the acid (of which there are two for a monoprotic acid, three for a diprotic acid), as well as the respective rates of reaction of the different protonated... 

The Michael addition mechanism, whereby sulfur nucleophiles react with organic molecules containing activated unsaturated bonds, is probably a major pathway for organosulfur formation in marine sediments. In reducing sediments, where environmental factors can result in incomplete oxidation of sulfide (e.g. intertidal sediments), bisulfide (HS ) as well as polysulfide ions (S 2 ) are probably the major sulnir nucleophiles. Kinetic studies of reactions of these nucleophiles with simple molecules containing activated unsaturated bonds (acrylic acid, acrylonitrile) indicate that polysulfide ions are more reactive than bisulfide. These results are in agreement with some previous studies (30) as well as frontier molecular orbital considerations. Studies on pH variation indicate that the speciation of reactants influences reaction rates. In seawater medium, which resembles pore water constitution, acrylic acid reacts with HS at a lower rate relative to acrylonitrile because of the reduced electrophilicity of the acrylate ion at seawater pH. 

Miller, B., Reactions of 4-bromocyclohexadienones with nucleophiles containing phosphorus and sulfur, J. Org. Chem., 28, 345, 1963. 

Sulfonation of 2-hydroxy-nicotinic acid 191 with sulfuric acid does not work but 30% oleum, that is sulfuric acid containing a 30% excess of S03, gives a 90% yield of 190. This might easily occur by iV-sulfonation 192, addition of some nucleophile 193, [1,5] shift 194 and elimination. Note that the position between C02H and N in 192 is blocked by the OH group so addition must occur on the other side in contrast to 184. This compound will also be discussed in chapter 33. 

Glemser, O. Shreeve, J.M. FluoridelonInducedCyclizationof Trifluoroacetonitrile with Oxygen- and Sulfur(II)-Containing Nucleophiles. Inorg. Chem. 1979, 18, 2319-2321. 

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