Sulfur derivatives

All these syntheses of non-anomeric C-branched sugars show the influence of neighboring oxygenated groups as for the the preceding photosubstitutions at the anomeric positions. The importance of stereoelectronic effects seems predominant for all these radical reactions. 

Ar= Ph, p-MeC6H4, or 2-naphthyl E = alkyl, benzyl, COCH3, or COPh Y = COOEt or 4-pyridyl 

Treated with ZnBr2 followed by enamines, phenyl thioethers 829 derived from aryl aldehydes are converted to (l-(phenylthio)alkyl ketones or aldehydes 830 in moderate to good yields (Equation 19). Enamines used in these syntheses are (1) morpholine enamine derived from diethyl ketone, (2) diethylamine enamine of propiophenone, (3) piperidine enamine derived from isovaleraldehyde, and (4) pyrrolidine enamine of cyclohexanone 2000H(53)331 . 

The amidoxims are formed by direct union of the nitrils with hydroxylamin, and have the general formula R—The 

Siilfur and oxygen, being equal in valence, may replace each other in organic compounds as, for instance, in sulfocyanlc acid CNSH, corresponding to cyanic CNOH. 

There exist many derivatives of the parafdns in which S thus takes the place of 0. Thus  

Uethyl SuMds.—Three are known. The monosuliid, (CH,),S, is a colorless liquid, boils at 41° (10o°.8 P.), has a very disagreeable odor, as have all the alcoholic sulflds and sulfhydrates. It is formed by the action of gaseous methyl chlorid on potassium monosulfid. The bisulfid, (CH,),S, is similarly formed from potassium bisulfld, and is a colorless liquid, boiling at 116°-118° i(340°.8-344°.4 P.). The trisulfid, (CH,),S, is formed in the same way from potassium pentasulfid, and boils at 200° (392° P.). 

Ethyl suMds are formed in the same manner as the methyl compounds, and have the same constitution. 

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Commercial monochloroacetic acid contains many other organic acids, particularly dichloroacetic acid [79 3-6] CI2CHCOOH, which has to be completely converted iato sulfur derivatives to avoid residual chlorine compounds which are harmful for cosmetic apphcations (8). Thioglycohc acid, which has to meet cosmetic specifications, must be free of metal impurities, and must be pure enough to avoid color and odor problems. 

Conversion to a more facile, sulfur-derived, leaving group can be achieved by treatment with sodium thiosulfate or salts of thio and dithio acids (75,87). Under anhydrous conditions, boron tribromide converts the 3 -acetoxy group to a bromide whereas trimethyl silyl iodide gives good yields of the 3 -iodide (87,171,172). These 3 -halides are much more reactive, even when the carboxyl group is esterified, and can be displaced readily by cyano and by oxygen nucleophiles (127). 

Divalent Sulfur Derivatives. A diaLkyl ester of thiodipropionic acid (16) is capable of decomposing at least 20 moles of hydroperoxide (17). Some of the reactions contributing to the antioxidant activity of these compounds are shown in Figure 3. 

Benzo derivatives show at least two, and up to seven, maxima in the range 200-320 nm (Table 24). The longest wavelength maximum occurs at 275-315 nm and generally at rather longer wavelengths for the sulfur derivatives than for their N or O analogues, and also for the benzo[c] compared with the benzo[f>] derivatives. 

Of much greater promise than thermolysis for the detection of oxirene is low-temperature photolysis. Strausz and coworkers (80JOC2271) investigated the photolysis, in an argon matrix at low temperatures, of 1,3-dioxolenone (vinylene carbonate 125). However, the only C2H2O species detected was ketene. The sulfur derivatives of (125), compounds (126) and... 

A carbonyl group can be protected as a sulfur derivative—for example, a dithio acetal or ketal, 1,3-dithiane, or 1,3-dithiolane—by reaction of the carbonyl compound in the presence of an acid catalyst with a thiol or dithiol. The derivatives are in general cleaved by reaction with Hg(II) salts or oxidation acidic hydrolysis is unsatisfactory. The acyclic derivatives are formed and hydrolyzed much more readily than their cyclic counterparts. Representative examples of formation and cleavage are shown below. 

Silyl-derived protective groups are also used to mask the thiol function. A complete compilation is not given here since silyl derivatives are described in the section on alcohol protection. The formation and cleavage of silyl thioethers proceed analogously to simple alcohols. The Si—S bond is weaker than the Si—O bond, and therefore sulfur derivatives are more susceptible to hydrolysis. For the most part silyl ethers are rarely used to protect the thiol function because of their instability. Silyl ethers have been used for in situ protection of the — SH group during amide formation. ... 

According to the systematic nomenclature these substances were first named l-f-triazolo[d] pyrimidines in compliance with the general principles of the Ring Index/ More recent papers and Chemical Abstracts indexes use the term i -triazolo[4,5-d]pyrimidine (147) in accord with the lUPAC nomenclature. The numbering of substituents when using the last-mentioned name is different from that of the 8-aza analogs. For the formulas of oxygen and sulfur derivatives names derived from the lactim or thiolactim form are almost exclusively in use (in common with the purine derivatives). These derivatives are thus described as hydroxy and mercapto derivatives, respectively. The name 1,2,3,4,6-pentaazaindene is used only rarely for this system. 

The TJV spectra were measured for practically all the numerous derivatives. Beside the analytical application of these to demonstrate the position of the substituent no detailed interpretation was attempted, however. On the whole, they are similar to the spectra of analogous purine derivatives and also display a similar dependence on Despite the fact that the question of structure with regard to the lactim-lactam (or thiolactim-thiolactam) tautomerism has not been studied in detail, it can be assumed that oxygen and sulfur derivatives, at variance with the conventional way of writing the formulas, possess a lactam or thiolactam structure. This is in agreement with the views on the analogous purine derivatives. 

A. B. Sheremetev and E. V. Shatunova, in XX All-Russian Conference on Chemistry and Technology of Organic Sulfur Derivatives, Conf. Abstr. Book, Kazan, 18-23 Oetober, 1999, p. 78 (in Russian). 

Selenium dioxide oxidation of 7,8-dihydro-5(6//)-quinolinone semicarbazone gave, in addition to the expected 4,5-dihydro selenadiazoloquinoline 95 (analogous to sulfur derivative 76), the oxidized l,2,3-selenadiazolo[4,5-/]quinoline 96, which, when heated to 210°C for 30 min, gave the dimeric [l,4]diselenino [2,3-/ 5,6-/ ]diquinoline (95JHC177). 

Bromine number (ASTM D-1159) and bromine index (ASTM D-2710) are qualitative methods to measure the reactive sites of a sample. Bromine reacts not only with olefm bonds, but also with basic nitrogen molecules and with some aromatic sulfur derivatives. Neverthele.ss. olefins are the most common reactive sites and the bromine number is used to indicate olefinicity of the feed. 

Fig. 14. Solid-state NMR spectrum of an acetylated lignosulphonic acid (A) and corresponding spectrum of its demethylated sulfur derivative (B), 441...

Keywords. Phosphorus and sulfur derivatives, Dithioesters, Hetero Diels-Alder, Sigmatropic rearrangements. Chiral ligands... 

There are two possibilities here to explain this correlation. One is that isotopically heavy sulfide sulfur derived from seawater sulfate was fixed in shale because reducing agency of shale with carbonaceous matters is thought to be stronger than that of sandstone. The ore fluids extracted this sulfur. Gold of low NAg precipitated in shale like the Kuryu deposit under more reducing environment than in sandstone like the Saigane deposit. 

Let us now discuss some of the characteristics of this quenching with mercaptans and disulfides. Interestingly, both sulfur derivatives are equally effective in inhibiting the photoreduction and are in fact interconverted during the reaction. The same equilibrium mixture of mercaptan and disulfide is obtained regardless of which was initially added to the reaction mixture. Furthermore, there appears to be no appreciable consumption of the sulfur compounds/64 When benzophenone is irradiated in the presence of isopropanol (OD) and mercaptan, isopropanol containing two deuterium atoms is isolated,... 

Imido chalcogen halides of the type RNEC12 (E=S, Se, Te) provide an interesting illustration of the reluctance of the heavier chalcogens to form -N=E< double bonds. The sulfur derivatives RNSX2 (X=F, Cl) are stable, monomeric compounds. 

The pendent unsaturation provides a site for vulcanization or cross-linking, e.g., by sulfur derivative. 

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