Sulfur—carbon bonds reactions with

The templates can be simply coordinated rather than attached. For example, complex 100 directed the radical relay chlorination to C-9, although the process was not as clean as with the attached templates [173]. We also used template-directed chlorina-tions to determine the conformations of flexible chains, just as we had previously with the benzophenone probes [174]. Also, by use of a set of tandem free radical chain reactions we could direct the formation of carbon-bromine and carbon-sulfur bonds, again with geometric control by the attached template [175]. 

Different alcohols and protected alcohols (as hemiacetals, silyl, methoxymethyl or phenyl ethers) were lithiated at the d-position to give the corresponding organolithium compounds. In the case of alcohols, a previous deprotonation of the hydroxyl functionality is required. The chiral intermediate 197 was prepared from the phenylsulfanyl derivative 196 first by deprotonation followed by carbon-sulfur bond cleavage with LiDTBB at low temperature. The reaction of the dianionic system 197 with y- and d-lactones in the presence of cerium(III) salts gave, after hydrolysis, spiroketal pheromones 198 (Scheme 2.27) [163]. 

The carbon sulfur bond in LTC4 is formed by the reaction of glutathione (Section 15 13) with leukotriene A4 (LTA4) LTA4 is an epoxide Sug gest a reasonable structure for LTA4... 

Carbon—Sulfur Cleavage. The carbon—sulfur bond of DMSO is broken in a number of reactions. Attempts to form the DMSO anion by the reaction of DMSO with sodium result in cleavage accompanied by methane evolution (eqs. 10 and 11) (43) ... 

Carbon-sulfur bonds can be formed by the reaction of elemental sulfur with a lithio derivative, as illustrated by the preparation of thiophene-2-thiol (201) (700S(50)104). If dialkyl or diaryl disulfides are used as reagents to introduce sulfur, then alkyl or aryl sulfides are formed sulfinic acids are available by reaction of lithium derivatives with sulfur dioxide. 

In the reactions of arylsulfenyl chlorides with enamines one encounters an unusual result for enamine chemistry, in that the formation of 2,6-disubstituted cyclohexanone enamines predominates over the formation of monosubstitution products 474). A rationalization of this result suggests the formation of an intermediate which can act as an intramolecular electrophile in formation of the second carbon-sulfur bond. 

Unexpectedly, neither direct complexation nor the deoxygenated complexes 95 or 96136,137 were observed in the reaction of diphenylthiirene oxide (18a) with iron nonacarbonyl. Instead, the red organosulfur-iron complex 97138 was isolated12, which required the cleavage of three carbon-sulfur bonds in the thiirene oxide system (see equation 33). The mechanism of the formation of 97 from 18a is as yet a matter of speculation. 

The reaction of crotonaldehyde and methyl vinyl ketone with thiophenol in the presence of anhydrous hydrogen chloride effects conjugate addition of thiophenol as well as acetal formation. The resulting j3-phenylthio thioacetals are converted to 1-phenylthio-and 2-phenylthio-1,3-butadiene, respectively, upon reaction with 2 equivalents of copper(I) trifluoromethanesulfonate (Table I). The copper(I)-induced heterolysis of carbon-sulfur bonds has also been used to effect pinacol-type rearrangements of bis(phenyl-thio)methyl carbinols. Thus the addition of bis(phenyl-thio)methyllithium to ketones and aldehydes followed by copper(I)-induced rearrangement results in a one-carbon ring expansion or chain-insertion transformation which gives a-phenylthio ketones. Monothioketals of 1,4-diketones are cyclized to 2,5-disubstituted furans by the action of copper(I) trifluoromethanesulfonate. ... 

Oxidation reactions using mediators are possible under very mild conditions with high selectivity. In fact, the oxidative cleavage of the carbon-sulfur bond of thio ether (16) was easily possible by using mediator (17) (Scheme 6) [46]. 

Thus, as compared with direct electrolysis, not only a gain in energy can be obtained but also the selectivities can be enhanced. The selectivity of the reaction in this case is determined by the potential differences between the different functional groups of the substrate and the mediator in combination with the rate of the respective follow-up reaction. A typical example of this type is the cleavage of a carbon-sulfur bond using tris(4-bromophenyl)amine as organic mediator ) (Eq. (12)). 

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