Sulfur acyclic compounds containing

Acyclic organic compounds containing an E-N (E=S, Se, Te) functional group are conveniently divided into those in which the organic group is attached to (a) nitrogen or (b) sulfur. 

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. 

NAPHTHENIC ACIDS. The term naphthenic acid, as commonly used in the petroleum industry, refers collectively to all of the carboxylic adds present m crude oil. Naphthenic adds are classified as monobasic carboxylic acids of the general formula RCOOH, where R represents the naphthene moiety consisting of cyclopentine and cyclohexane derivatives. Naphthenic adds are composed predominantly of alkyl-substituted cycloaliphatic carboxylic adds, with smaller amounts of acyclic aliphatic (paraffinic or fatty) acids. Aromatic, okfinic. hydroxy, and dibasic acids are considered to be minor components. Commercial naphthenic aads also contain varying amounts of unsaponifiable hydrocarbons, phenolic compounds, sulfur compounds, and water. The complex mixture of adds is derived from straight-run distillates of petroleum, mostly from kerosene and diesel fractions. See also Petroleum. 

As was the case for the corresponding compounds containing oxygen (i.e., ethers) and sulfur (i.e., thioethers or sulfides) and as shown briefiy above, amines also occur both in acyclic and cyclic forms. Thus, compounds directly analogous to the common cyclic ethers and thioethers vide supra) are known and they are shown below. The trivial names that are most widely used for these amines, along with more systematic names, are provided. Generally, the common names will be used. 

A more common usage of phosphorus pentasulfide is to effect replacement of oxygen atoms in an acyclic compound. The thiated intermediate—which may be a fairly complex derivative containing phosphorus, sulfur, and oxygen atoms—then cyclizes with elimination. Except in one case, mentioned below, the intermediates seem not to have been studied in any detail. 

Sulfur-containing acyclic and cyclic compounds have been prepared from allenyl sulfides in numerous transformations such as substitutions, additions, cydoaddi-tions and other cyclization reactions. Like the other donor-substituted allenes, allenyl sulfides are suitable substrates for regioselective lithiation and substitutions as exemplified in Scheme 8.86 [168, 169,175]. 

In contrast to the other large cats, the urine of the cheetah, A. jubatus, is practically odorless to the human nose. An analysis of the organic material from cheetah urine showed that diglycerides, triglycerides, and free sterols are possibly present in the urine and that it contains some of the C2-C8 fatty acids [95], while aldehydes and ketones that are prominent in tiger and leopard urine [96] are absent from cheetah urine. A recent study [97] of the chemical composition of the urine of cheetah in their natural habitat and in captivity has shown that volatile hydrocarbons, aldehydes, saturated and unsaturated cyclic and acyclic ketones, carboxylic acids and short-chain ethers are compound classes represented in minute quantities by more than one member in the urine of this animal. Traces of 2-acetylfuran, acetaldehyde diethyl acetal, ethyl acetate, dimethyl sulfone, formanilide, and larger quantities of urea and elemental sulfur were also present in the urine of this animal. Sulfur was found in all the urine samples collected from male cheetah in captivity in South Africa and from wild cheetah in Namibia. Only one organosulfur compound, dimethyl disulfide, is present in the urine at such a low concentration that it is not detectable by humans [97]. 

Table 4 Total energies ( ) of the sulfur-containing compounds c/s-26b,d and 19b,d, and the differences in the energies for acyclic and cyclic structures (AE20 i9), from ab initio calculations at HF and electron-correlated MP2 levels...

Oxygen-containing heterocycles are always less aromatic than their sulfur and nitrogen counterparts, e.g., imidazole thiazole >> oxazole and pyrazole > isothiazole > isoxazole. These trends follow those of pyrrole, thiophene and furan (Section 2.3.4.2). 1,2,3-Oxadiazole is unknown and all attempts to synthesize this compound have been unsuccessful. Although it is not the least aromatic of the oxadiazoles based on the HOMA index (cf. 1,3,4-oxadiazole), its instability can be attributed to easy isomerization to the acyclic valence tautomer (i.e., 85 - 86). 

Tris-heterosubstituted organolithium compounds are considered as carboxyl anions and related synthons. Tris(methylsulfanyl)- and tris(phenylsulfanyl)methyllithium, 496 and 497, and other acyclic tris(alkylsulfanyl)methyllithiums 498-500 and cyclic ones 501 and 502 have been described as sulfur-containing LiCXYZ compounds12,684 687. 

The thioacylated products are frequently useful intermediates and they have been transformed into sulfur-containing heterocyclic compounds. Reflux of acyclic 1,1-enediamines 176 with phenacyl bromide or chloroacetone in ethanol gives the tetra-substituted thiophenes 178142. The reaction includes 5-alkylation and cyclization steps (equation 70). 

Acyclic compounds wherein the acid radical contains sulfur... 

The methods of synthesis for bis(perfluoroalkyl)furans are more developed. For example, 2-methyl-3,4-bis(trifluoromethyl)furan can be synthesized by the reaction of 2-methyl-furan-3,4-dicarboxylic with sulfur tetrafluoride. However, the main synthetic methods rely on the use of unsaturated fluorine-containing acyclic compounds. So, 3-trifluoromethylfurans 57 were prepared from p,p-bis(trifluoro-methyl)a,p-unsaturated ketones and tin(II) chloride. ... 

Oxygen- and sulfur-containing macrocyclic compounds show much of the same functional group chemistry expressed in the simple acyclic systems. For example, as shown in Scheme 4, the macroring... 

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