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Tetracoordinated sulfur compound

Glasses, both having distorted tetrahedral geometry. Optically active tetracoordinate sulfur compounds having trigonal bipyramidal structure (sulfuranes) have become available relatively recently. [Pg.336]

A different approach to the stereospecific synthesis of sulfinamides described by Johnson (117,118) is based on the conversion of suitable chiral tetracoordinate sulfur compounds into sulfinamides. It was shown (117) that optically active methyl phenyl sulfoximide undergoes a clean and stereospecific reduction to the corresponding sulfinamide by means of aluminum amalgam. On the other hand,... [Pg.358]

Oxosulfonium salts of the general formula shown in 134 belong to a group of tetrahedral tetracoordinate sulfur compounds with four different ligands. Therefore, they are chiral at sulfur and can exist in the form of optical isomers. Thus far, however, methylethylphenyl-... [Pg.373]

Among chiral tetracoordinate sulfur compounds, most information is available on sulfoximides, which may be considered to be the mononitrogen analogs of sulfones. [Pg.375]

Tetracoordinate sulfur compounds containing a lone pair of electrons at sulfur possess a more or less distorted trigonal-bipyramidal structure, in common with the vast majority of other pentacoordinated molecules of the main group elements (189,191,199). A common name, sulfurane, is generally accepted for this type of compound. In principle, sulfuranes are chiral. However, both the number of optically active isomers and their optical stability depend on the nature of substituents bonded to the central sulfur atom, the apicophilicity of the substituents, and the energy required for permutational isomerization processes. In this context it is interesting to note that acyclic sulfuranes with four different ligands should exist in 20 isomeric forms. [Pg.384]

Finally, it should be stressed that various nucleophilic and electrophilic reactions that lead from sulfoxides and sulfinates of known absolute configuration to new chiral tri- and tetracoordinate sulfur compounds and follow a stereochemically unambiguous course can be utilized for configurational assignments. Some of these reactions... [Pg.393]

As the last point in Sect. IV, we discuss briefly the reactions of chiral sulfur compounds with electrophilic reagents. In contrast to nucleophilic substitution reactions, the number of known electrophilic reactions at sulfur is very small and practically limited to chiral tricoordinate sulfur compounds that on reacting with electrophilic reagents produce more stable tetracoordinate derivatives. It is generally assumed that the electrophilic attack is directed on the lone electron pair on sulfur and that the reaction is accompanied by retention of configuration. As typical examples of electrophilic reactions at tricoordinate sulfur, we mention oxidation, imination, alkylation, and halogenation. All these reactions were touched on in the section dealing with the synthesis of chiral tetracoordinate sulfur compounds. [Pg.431]

The O-trimethylsilyl derivative (212) of dibenzothiophene 5-oxide on treatment at — 78°C with 2,2 -dilithiobiphenyl gave the first stable tetracoordinated sulfur compound with four C-S bonds (213) in 96% yield (92CC1141). [Pg.335]

Previously, the same author [52] reported that compounds containing the tricoordinated sulfur cation, such as the triphenylsulfonium salt, worked as effective initiators in the free radical polymerization of MMA and styrene [52]. Because of the structural similarity of sulfonium salt and ylide, diphenyloxosulfonium bis-(me-thoxycarbonyl) methylide (POSY) (Scheme 28), which contains a tetracoordinated sulfur cation, was used as a photoinitiator by Kondo et al. [63] for the polymerization of MMA and styrene. The photopolymerization was carried out with a high-pressure mercury lamp the orders of reaction with respect to [POSY] and [MMA] were 0.5 and 1.0, respectively, as expected for radical polymerization. [Pg.379]

We hope that this review of chiral sulfur compounds will be useful to chemists interested in various aspects of chemistry and stereochemistry. The facts and problems discussed provide numerous possibilities for the study of additional stereochemical phenomena at sulfur. As a consequence of the extent of recent research on the application of oiganosulfur compounds in synthesis, further developments in the field of sulfur stereochemistry and especially in the area of asymmetric synthesis may be expected. Looking to the future, it may be said that the static and dynamic stereochemistry of tetra- and pentacoordinate trigonal-bipyramidal sulfur compounds will be and should be the subject of further studies. Similarly, more investigations will be needed to clarify the complex nature of nucleophilic substitution at tri- and tetracoordinate sulfur. Finally, we note that this chapter was intended to be illustrative, not exhaustive therefore, we apologize to the authors whose important work could not be included. [Pg.457]

Dahl and co-workers prepared the unusual compound Mo2Re2(Cp)2(CO)u(S)2 (42) containing both tri- and tetracoordinated sulfur ligands, Eq. (107) (158). [Pg.266]

In contrast to the thiophene 1,1-dioxides, the tetracoordinated sulfur atom in the unsymmetrically substituted sulfoximide 132 is chiral. The compound could be separated into two enantiomers, and the absolute configuration established by X-ray crystallography. [Pg.789]

Akiba et al have provided tetracoordinated sulfuranes by the demethylation of a series of sulfur compounds such as 36, having an equatorial methyl ligand,... [Pg.109]

Section 7.16 Atoms other than carbon can be chirality centers. Examples include those based on tetracoordinate silicon and tricoordinate sulfur as the chirality center. In principle, tricoordinate nitrogen can be a chirality center in compounds of the type N(x, y, z), where x, y, and z are different, but inversion of the nitrogen pyramid is so fast that racernization occurs vit -tually instantly at room temperature. [Pg.318]

There are some unique structural aspects of some of the sulfur fluorides that will need to be discussed in order to understand the 19F NMR spectra. The geometry of tetracoordinate group VI compounds is predicted on the basis of Gillespie s electron-pair repulsion theory to be trigonal bipyramid, with an electron pair occupying one of the equatorial sites.2 Thus, the SF3 substituent as well as the molecule SF4 have structures as depicted in Scheme 7.12, with nonequivalent (axial and equatorial) fluorines, and thus their 19F NMR spectra consist of two 19F signals, with the fluorines being coupled if the system is scrupulously dry. [Pg.227]

The reaction of 3-mercaptoloindole 45 with the chlorides of the acids of tetracoordinated phosphorus [12] takes place under more rigorous conditions (boiling benzene) than with the derivatives of P(III) acids. According to 31P NMR and IR spectroscopy, phosphorylation takes place at the sulfur atom with the formation of only one compound 124. [Pg.22]

The necessary criterion that an object not be superimposable on its mirror image can be met by compounds in which the chiral center is other than tetracoordinate carbon. Many such examples are known, including sulfoxides in which the substituents on sulfur are different. These molecules are nonplanar, with significant barriers to pyramidal inversion. [Pg.41]


See other pages where Tetracoordinated sulfur compound is mentioned: [Pg.198]    [Pg.362]    [Pg.198]    [Pg.362]    [Pg.335]    [Pg.2]    [Pg.726]    [Pg.726]    [Pg.161]    [Pg.222]    [Pg.89]    [Pg.355]    [Pg.161]    [Pg.2]    [Pg.612]    [Pg.205]    [Pg.528]    [Pg.1406]    [Pg.1156]    [Pg.15]    [Pg.1156]    [Pg.528]    [Pg.6]    [Pg.152]    [Pg.114]    [Pg.2]    [Pg.5]    [Pg.1406]   
See also in sourсe #XX -- [ Pg.335 ]




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