Sulfide precursor

Ethylene glycol has been used instead of water as solvent in the deposition of CdS films from cadmium acetate and sodium sulfide precursors. The films were amorphous and showed some excess cadmium (Cd/S atomic percentage ratio was 52.3/47.7) in EDX analysis.79... 

SnS2. Weakly crystalline SnS2 films have been grown from tin(II) chloride and sodium sulfide precursors. EDX analysis gave a Sn/S ratio of 1/2.02. The surface roughness of a 290-nm-thick film was 32 nm. The band gap was 2.22 eV, and the photoluminescence spectra, using a 325 nm excitation source, showed peaks at 549 nm and 700 nm.118... 

T(—H) can also be formed in a two-step process involving radical cation formation produced by photosensitizers operating through a type I mechanism, followed by deprotonation. Cadet has also developed the photolabile phenyl sulfide precursor that upon irradiation at 254nm generates T(—H). " The corresponding phenyl selenide" and methoxy-substituted sulfides" were developed by the Greenberg... 

Phenylthiazirene (34) was considered to be the most reasonable nitrile sulfide precursor but no spectral peak could be assigned unambiguously to this otherwise unknown compound <78JCS(P1)746>. 

Ethylidenation. Flclquist et al. have extended the cyclopropanation of olefins with an iron methylene complex (9, 143) to ethylidenation of olefins with the iron cthylidcnc complex 1. Since the sulfide precursor (2) is more stable, the reagent is generated in the presence of the olefin. The reagent gives methyl-substituted cyclo-... 

Sulfoxide and sulfone derivatives are best prepared by oxidation of a sulfide precursor, though specific 2-substitution may be achieved via metallation of the oxidized system, as outlined in Section 2.25.3.1. 

The sulfonimide (238) has been copolymerized with CH2=CHCN and CH2=C(Me)C02Me to produce a useful fibre (75GEP2346566), and the bis(oxathiazolone) (239), as a nitrile sulfide precursor (Scheme 5), has been used in the vulcanization of SBR... 

Finally, a thia Diels-Alder reaction representing a less common cycloaddition type in natural product synthesis shall be discussed. Thus, Vedejs et al. have included such a cycloaddition into an elegant strategy aimed at the synthesis of macrocyclic [ll]-cytochalasans such as zygosporin E 7-76 [536-538]. Thus, release of the thioaldehyde 7-73 from its phenacyl sulfide precursor in the presence of the silyloxydiene 7-74 yielded 7-75 as 2 1 mixture with its C20 epimer. Fortunately, equilibration of this mixture raised the ratio up to 10 1. Several subsequent steps yielded the tetracyclic intermediate 7-77 cleavage of its thioether moiety then liberated the 11-membered macrocycle present e.g. in zygosporin E 7-76 (Fig. 7-16). 

Also, the rigidification of the galactose ring was not sufficient to block the elimination of the 2-azido substituent of 17 even using the low-temperature reagent (Fig. 5). Another failure occurred with the isoxazole sulfone 19. Here, the heterocycle did not survive base treatment. The isoxazole sulfide precursor was also unstable to base (Fig. 6). 

Phenyl sulfides are more reactive than ethers, yet the sulfide precursors do not couple with organolithiums. 

P.B. Alper and co-workers developed a practical approach for the synthesis of 4,7-disubstituted indoles based on the Sommeiet-Hauser rearrangement of aryl sulfilimines. The multihundred-gram preparation of methyl 7-chloroindole-4-carboxylate was achieved. The synthesis commenced with the activation of a sulfide precursor with SOCI2 and coupling the intermediate with 3-amino-4-chlorobenzoate to afford an aromatic sulfilimine. This sulfilimine was exposed to excess triethylamine and heated to generate the sulfonium ylide that underwent the rearrangement. 

III-VI thin films have primarily involved single-source precursors, and this area has been reviewed [209]. Table 5-12 summarizes selected gallium and indium sulfide precursor compounds, along with the phase observed in the resulting CVD films. 

Investigation into new thio-acid compounds from oxide, hydroxide, and sulfide precursors is being excuted. One new compound has recently demonstated lO S/cm at 100°C. 

Direct precipitation of pyrite without intermediate iron sulfide precursors was reported for salt marsh sediments, where pore waters were undersaturated with respect to amorphous FeS but oversaturated with respect to pyrite (Howarth 1979 Giblin and Howarth 1984). In these sediments, the oxidizing activity of the roots favored the formation of elemental sulfur and polysulfides which were thought to react directly with Fe +. The direct reaction pathway may proceed within hours, resulting in the formation of single small, euhedral pyrite crystals (Rickard 1975 Luther et al. 1982). Framboidal pyrite, apart from that formed by the mechanism presented by Rickard (1997), is formed slowly (over years) via intermediate iron sulfides (Sweeney and Kaplan 1973 Raiswell... 

The reaction chemistiy of aziridines is underdeveloped. This is particularly surprising because aziridines are easily prepared in high enantiomeric purity. Arlette Solladie-Cavallo of the Universite L. Pasteur, Strasbourg, reports J. Org. Chem. 2004, 69, 1409) that addition of the pulegone-derived sulfonium ylide 6 to an aldehyde tosylimine. such as 7 proceeds to give the N-tosyl aziridine 8 in high ee and with good diastereocontrol. The sulfide precursor to 6 is recovered in almost quantitiative yield. N-Tosyl aziridines such as 8 are readily opened both by carbon and by heteroatom nucleophiles. 

Application of the Kagan method as reported in the literature effectively led to the production of racemic omeprazole. Formation of the racemate was rationalized by the similar steric demand of the two substituents of the sulfide precursor (pyrmetazole). Preparation of the catalyst complex at 30 °C, in the presence of water and the sulfide, and the use of Af,Af-diisopropylethylamine (DIEA) as... 

A variety of sulfide precursors can be used to prepare CdS QDs, including thiourea (A. Aboulaich, D. BiUaud, M. Abyan, L. Balan, J.-J. Gamnet, G. Medjadhi, J. Ghanbaja, R. Schneider, ACS Appl. Mater. Interfaces, 2012,4,2561). 

The regulation of the biosynthetic pathway for cysteine appears to present the plant with a variety of problems, (a) The formation of cysteine represents the confluence of two separate pathways which produce OAS and the sulfide precursor. Are the rates of these pathways coordinated Is cysteine formation ordinarily limited by the availability of sulfide, OAS, neither, or both (b) In plants, synthesis of sulfide occurs via a pathway which branches after APS to lead to sulfide or to PAPS, the precursor of sulfate esters and, probably, of sulfonolipids. If sulfide formation is regulated, how is provision... 

An important proviso of this scheme is that under normal conditions the rate of synthesis of cysteine is limited by the availability of its sulfide precursor. Then, changes in the rate of formation of sulfide will be closely coupled to changes in the rate of cysteine formation. Evidence in support of the limitation of the rate of cysteine biosynthesis by the availability of sulfide includes the following, (a) The concentration of acid-volatile sulfide in L. minor growing on sulfate is about 11 fxM (Brunold and Schmidt, 1978), while the of cysteine synthase for sulfide is at least 180 f/M (Table II). This comparison suggests that cysteine synthase may normally be operating below its for sulfide, (b) Administration of H2S (18 ppm in the gas phase) to L. minor caused about a 50% increase in the steady-state concentration of soluble cysteine in the plants within a few minutes (Brunold and Erismann,... 

In another report using the same method ethylene glycol was used as solvent and composition of the CZTS nanocrystals was controlled by varying the parameters like precursors concentrations, reaction temperature and residence time. Growth of CZTS nanocrystals from binary metal sulfide precursors was studied in detail as well. Average size of the nanoctystals obtained was 5.4 nm 2.0 nm. 

Schemes 20.4 and 20.5 summarize some of the most useful methods for obtaining Pummerer substrates. As sulfides are generally the starting materials for preparing sulfoxides. Scheme 20.4 also highlights methods to generate those sulfide precursors. ...

Biological Ethion degraded in lagoonal sediments obtained at various sites in the Indian River between Cape Kennedy and Vero Beach, FL. In 14 sediment samples enriched with ethion, 8 exhibited iron sulfide (precursor hydrogen sulfide) production following 20... 

There are many synthetic techniques for stereoselective synthesis and because of the importance much research is currently devoted to expanding these techniques. Omeprazole, marketed as Prilosec , was the first proton pump inhibitor and is used as a treatment for gastric ulcers. It is a racemic mixture. The S enantiomer has better pharmacokinetics and pharmacodynamics than the racemic mixture and therefore higher efficacy in controlling acid secretion [38]. The S enantiomer is called esomeprazole and is marketed as Nexium . Nexium has annual sales of 8.4 billion [39]. The chiral center is at the sulfur and the enantiomers can be separated by derivatizing with a R-(-) mandelic acid chiral auxiliary to form two diastereomers. Unlike enantiomers, diastereomers have different physical properties. The diastereomers can be separated by HPLC and then the chiral auxiliary removed to afford each of the omeprazole enantiomers. Alternatively, the sulfide precursor can be asymmetrically oxidized to form esomeprazole in 99.99% enantiomeric excess (ee) [40]. Enantiomeric excess means the excess amount of one enantiomer over the racemic mixture. If something is 80% ee that means that 20% is a racemic mixture and the other 80% is excess of that enantiomer. In this example, for 100 g, there are 90 g of the predominant enantiomer and 10 g of the lesser enantiomer in other words, 20 g is a racemic mix (lOg of each enantiomer) and 80g is excess enantiomer. 

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