Sulfur—carbon bonds group

The changes in the sulfur-carbon bonds appear to be especially sensitive to the nature of the R groups1 °. As R is usually a group of atoms, the relative conformation of these groups in terms of torsion angles with respect to the S—C bonds is often important. 

Electrophilic catalysis by Lewis acids is also observed here no ambiguity arises with general acid catalysis, as Lewis acids and proton acids are not the same. An interesting example is the strong catalysis of thiolester hydrolysis by mercuric and silver ions. These soft acids presumably coordinate with the sulfur and, by virtue of the consequent electron withdrawal, make the carbonyl group much more susceptible to attack in the addition mechanism, or, in favorable cases, promote unimolecular SN1 cleavage of the sulfur-carbon bond.122... 

It has been proposed that sulfur-carbon bonds break at lower thermal stress than carbon-carbon bonds in sulfur-rich kerogens (24). Scission of sulfur-carbon bonds provides one explanation for the observed depletion of organosulfur compounds in the pyrolysates of high rank coals. The sulfur groups present in low rank coals are broken from the coal matrix to produce low molecular weight sulfur compounds which are not measured by the techniques used in this study. 

Na or Li and ammonia, excellent yields. This is a very good method to remove a benzyl group from an amide and will usually work when hydrogenolysis does not. A dissolving metal reduction can be effected without cleavage of a sulfur-carbon bond. Note also the unusual selectivity in the cleavage illustrated below. This was attributed to steric compression. Primary benzyl amides are not cleaved under these conditions. ... 

The Corey-Winter reaction provides a useful method for the preparation of olefins that are not accessible by other routes. For instance it may be used for the synthesis of sterically crowded targets, since the initial attack of phosphorus at the sulfur takes place quite distantly from sterically demanding groups that might be present in the substrate molecule. Moreover the required vicinal diols are easily accessible, e.g. by the carbon-carbon bond forming acyloin ester condensation followed by a reductive step. By such a route the twistene 10 has been synthesized ... 

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