Thioethers structure

Using thiophenol instead of phenol, Michel et al. [49] found a new selective reaction that takes place exclusively with allylic chlorines and not with tertiary chlorines. A single product of thioether structure is formed [Eq. (11)]. 

Title Novel Sulfur-containing Phenolic Resin, Process for Preparing the Same, Phenol Derivatives Having Thioether Structure or Disulfide Structure, Process for Preparing the Same and Epoxy Resin Composition Adhesive... 

Substitution of alkyl and aryl groups for H on H2S yields thiols and sulfides (thioethers). Structural formulas of examples of these compounds are shown in Figure 17.2. 

As mentioned above, the title compounds are now known to constitute the active components of SRS-A, and as such have been the subject of intense biological and synthetic research. All the syntheses of these thioether structures have converged on LTA4 methyl ester, the various syntheses of which were outlined in Section 3.C. Three groups, that of Corey at Harvard University, the Merck Frosst Canada group, and workers at Hoffmann-La Roche, independently developed synthetic routes to LTA4 methyl ester and hence to various components of the SRS-A complex. 

The oxidation of various thioethers with aqueous H2O2, in organic solvents, over two titanium containing zeolites, TS-1 and Ti-beta has been studied. The performances of these catalysts depend strongly on the thioether structure and the nature of solvent. Thus, the reactivity of organic substrates is in agreement with the nucleophilic character of the sulfur atom and their molecular size (Ethyl)2 S > (Propyl)2 S > (Allyl)2 S > (Butyl)2 S > Methyl-S-Phenyl > (Phenyl)2 S. The conversion of sulfide in protic solvents is higher than that obtained in aprotic solvents. For all the solvents, Ti-beta is more active and selective than TS-1 in the oxidation of hindered molecules. 

The use of transition-metal (Ti, Mo, V, Fe, W, Re, Ru) complexes as active catalysts for the selective oxidation of thioethers by H2O2 in homogeneous conditions has been reported by various authors [3-10]. Recently, it has been shown that some of these metals (Ti,V) incorporated in a zeolitic framework, such as MFI or MEL, are able to catalyse the oxidation reaction of thioethers with H2O2 [11,12]. However, no detailed studies on this reaction are available. The scope of this work was to investigate the influence of thioether structure, solvent nature, reaction temperature and shape selectivity effect of catalyst on the performances of TS-1 and Ti-beta samples in the sulfoxidation of organic sulfides with H2O2... 

The oxidation of various thioethers with hydrogen peroxide has been carried out using TS-1 and Ti-beta as catalysts, in an organic solvent. The concentration of both substrate and H2O2 was 0.19 M. In this section we report the catalytic performances of these catalysts with respect to thioether structure, solvent nature and reaction temperature. 

Extension of the above isomeric mesogen (4) with linear ether or thioether structures, e.g. H0-(CH2-CH2-0)n-H where n=2,3 or 4 does not however form mesophasic polymers. The active mesogen structure appears to require three aromatic rings. If one of the rings is attached through a non-linear ether group then once again no mesophase is observed (e.g. 7). 

Influence of the Thioether Structure on the Synergism between Phenyl-Substituted Phenols and / -Activated Thioethers (Oven-Aging). 

Most conventionalr polysulfide sealants are based on disulfides. Recently, a new family of sulfur-containing sealants (121,122) has been developed based on thioethers (Fig. 19) The thioether structure is thermally more stable than the polysulfide, thus the upper operating temperature... 

The classical structures of pyrrole, furan and thiophene (31) suggest that these compounds might show chemical reactions similar to those of amines, ethers and thioethers (32) respectively. On this basis, the initial attack of the electrophile would be expected to take place at the heteroatom and lead to products such as quaternary ammonium and oxonium salts, sulfoxides and sulfones. Products of this type from the heteroaromatic compounds under consideration are relatively rare. 

A wide variety of /3-lactams are available by these routes because of the range of substituents possible in either the ketene or its equivalent substituted acetic acid derivative. Considerable diversity in imine structure is also possible. In addition to simple Schiff bases, imino esters and thioethers, amidines, cyclic imines and conjugated imines such as cinnamy-lidineaniline have found wide application in the synthesis of functionalized /3-lactams. A-Acylhydrazones can be used, but phenylhydrazones and O-alkyloximes do not give /3-lactams. These /3-lactam forming reactions give both cis and /raMS-azetidin-2-ones some control over stereochemistry can, however, be exercised by choice of reactants and conditions. 

AgN03, EtOH, Pyr, 90°, 1.5 h H2S, 47% yield. An 5-triphenylmethyl thioether can be selectively cleaved in the presence of an 5-diphenylmethyl thioether by acidic hydrolysis or by heavy-metal ions. As a result of the structure of the substrate, the relative yields of cleavage by AgN03 and Hg(OAc)2 can be reversed. 

Four different types of lipid-anchoring motifs have been found to date. These are amide-linked myristoyl anchors, thioester-linked fatty acyl anchors, thioether-linked prenyl anchors, and amide-linked glycosyl phosphatidylinosi-tol anchors. Each of these anchoring motifs is used by a variety of membrane proteins, but each nonetheless exhibits a characteristic pattern of structural requirements. 

The first three-dimensional macrobicyclic TTF derivatives have been obtained <96CC615> and work on TTF-containing crown ethers and thioethers has continued <96LA551, 96JCS(P1)1995> with structures of this type being used to obtain the first TTF-containing... 

In practice one can differentiate between two kinds of donors, the resulting donor-acceptor bonds can be largely ionic (class I) or covalent (class II) [16]. Donors of the first type (class I) stem from the first row of the periodic table of elements, such as amines, ethers, in detail structures in which the Lewis basis centre possessing the non-bonding lone pair is strong electronegative. Donors of the second type are constituted from elements of the second row of the periodic table of elements, such as phosphines, thioethers, etc. (class II). These Lewis donors are... 

In this progress report we have reviewed the latest developments in the large area of cationic low-coordinated species and their coordination with Lewis donors. It is clear that these species are of a broad interest, in particular for catalysis. In some cases, e. g. the methylene phosphenium cation, the donor adducts also open new routes for synthesis. Regarding the mechanism for the diverse donor-addition reactions, the structural details are only poorly understood and need a better classification. In particular the variation of the Lewis-donor has to be established. Hitherto in most cases iV-donation is studied. It includes amines or pyridines. Obviously the effect of other donors, such as phosphines, thioethers needs to be studied as well. The siliconium cation for which these effects are better known could provide an understanding for further investigations within this field. 

Primary phosphines (R-PHj) are an important ciass of compounds in organophosphorus chemistry. Aithough discovered over a century ago, their chemistry and appiications have gained prominence in recent years. This review discusses recent deveiopments on synthesis, moiecuiar structure, properties, and appiications of primary phosphines. In particular, discussions on synthesis and properties emphasize recent results from our laboratory on the chemical architecture of amide, thioether, and carboxylate functionalized primary bisphos-phines. The utility of bromo- and aminopropyl phosphines (X(CH2)3PH2 X=Br or NH2) as building blocks to produce designer primary phosphines that display exceptional oxidative stability is described. The review also discusses the utility of carboxylate functionalized primary phosphines for incorporation on to peptides and their potential applications in catalysis and biomedicine. 

A recently developed application of the Ramberg-Backlund reaction is the synthesis of C-glycosides. The required thioethers can be prepared easily by exchange with a thiol. The application of the Ramberg-Backlund conditions then leads to an exocyclic vinyl ether that can be reduced to the C-nucleoside.95 Entries 3 and 4 in Scheme 10.6 are examples. The vinyl ether group can also be transformed in other ways. In the synthesis of partial structures of the antibiotic altromycin, the vinyl ether product was subjected to diastereoselective hydroboration. 

---