From disulfides

A similar reaction from disulfide (261) and a-chloroalkanoic acids is reported by DahJbom (Scheme 134) (392). 

Chemisorption of alkanethiols as well as of di- -alkyl disulfides on clean gold gives indistinguishable monolayers (251) probably forming the Au(l) thiolate species. A simple oxidative addition of the S—S bond to the gold surface is possibly the mechanism in the formation of SAMs from disulfides ... 

Vinyllithium [917-57-7] can be formed direcdy from vinyl chloride by means of a lithium [7439-93-2] dispersion containing 2 wt % sodium [7440-23-5] at 0—10°C. This compound is a reactive intermediate for the formation of vinyl alcohols from aldehydes, vinyl ketones from organic acids, vinyl sulfides from disulfides, and monosubstituted alkenes from organic halides. It can also be converted to vinylcopper [37616-22-1] or divinylcopper lithium [22903-99-7], which can then be used to introduce a vinyl group stereoselectively into a variety of a, P-unsaturated systems (26), or simply add a vinyl group to other a, P-unsaturated compounds to give y, 5-unsaturated compounds. Vinyllithium reagents can also be converted to secondary alcohols with trialkylb o r ane s. 

Also, sulfinyl chlorides (precursors to sulfinate esters) have recently been prepared directly from disulfides (equation 3)23. 

Add 1-10 mg of a protein or antibody containing an available thiol group to the particle suspension. Alternatively, add the protein to be coupled to the particle suspension in an amount equal to 1-10 X molar excess over the calculated monolayer for the protein type to be coupled. The optimal amount of protein to be added should be determined experimentally. Creating thiol groups on proteins or peptides may be done from disulfides by reduction. Alternatively, a thiolation reagent may be used to add thiols to the protein surface for coupling (see the protocols in Chapter 1, Section 4.1). 

Because anhydrides of sulfenic acids have the thiolsulfinate structure they can also be formed from disulfides by oxidation. Treatment of a disulfide with one mole of peracid, for example, gives the corresponding thiolsulfinate (25a) (Small et al., 1947 Block and O Connor, 1974b). Murray and Jindal (1972)... 

The direct electrosynthesis of S—N bonds from disulfides and amines has been shown to occur through a reaction of the amine with the oxidized disulfide being a strong electrophile. In contrast to the results, the cross-coupling of phthahmide (16) with disulfide does not proceed in a direct electrolysis. However, the electrosynthesis of sulfenimides (17) can be achieved by a [Br]" "-mediated cross-coupling reaction of imides with disulfides (Scheme 7). The electrolysis of a mixture of (16) and dicyclohexyl disulfide in an MeCN-NaBr-(Pt) system affords... 

Bromide and iodide ions are not only effective as redox catalyst in the indirect electrochemical formation of carbon-hetero atom bonds but also of hetero-hetero atom bonds. Thus, the nitrogen-sulfur bond in sulfenimides (Eq. (53) Table 4, No. 33) and sulfenimines (Eq. (54) Table 4, No. 34) can be generated. The electrogenerated active bromine species forms a positively polarized sulfenyl intermediate from disulfides. 

Dual-electrode LCEC is very useful for the selective detection of chemically reversible redox couples. In this case, two electrodes are placed in series (Fig. 27.1 OB). The first electrode acts as a generator to produce an electroactive species that is detected more selectively downstream at the second electrode, which is set at a more analytically useful potential. One excellent example of the use of a dual-electrode detector for electrochemical derivatization is the detection of disulfides [34]. In this case, the first electrode is used to reduce the disulfide to the corresponding thiol. The thiol is then detected by the catalytic oxidation of mercury, described earlier. Because of the favorable potential employed at the second electrode, the selectivity and sensitivity of this method are extremely high. In addition, thiols can be distinguished from disulfides by simply turning off the generator electrode. 

Some of the above features can be seen in the spectra of cathepsin D (Fig. B3.5.10), where the intact single-chain bovine enzyme is compared with the same material cleaved at an exposed loop but without dissociation. The latter has 50% of the specific activity of the intact molecule. Phenylalanine residues can be seen to be present in specific environments in both forms. The fine structure of the Lb transition of tryptophan is superimposed on the broad peak of the La transition, which is apparently more intense in the intact enzyme. Alternatively, there could be a greater contribution from disulfide bonds, but the absence of ellipticity above 320 nm favors the former assignment and the CD is therefore consistent with a limited increase in dynamics of the molecule as a result of the chain... 

On the pages which follow, general methods are illustrated for the synthesis of a wide variety of classes of organic compounds including acyl isocyanates (from amides and oxalyl chloride p. 16), epoxides (from reductive coupling of aromatic aldehydes by hexamethylphosphorous triamide p. 31), a-fluoro acids (from 1-alkenes p. 37), 0-lactams (from olefins and chlorosulfonyl isocyanate p. 51), 1 y3,5-triketones (from dianions of 1,3-diketones and esters p. 57), sulfinate esters (from disulfides, alcohols, and lead tetraacetate p. 62), carboxylic acids (from carbonylation of alcohols or olefins via carbonium-ion intermediates p. 72), sulfoxides (from sulfides and sodium periodate p. 78), carbazoles... 

The reaction of 2,2,5,5,6,6,9,9-octamethyl-3,7-decadiyne 206 with S2C12 gave a 4/7,5/7-thiepine 209, as the sole product, in 99% yield <2000TL8349>. The formation of 209 was explained as shown in Scheme 27. The addition of S2C12 to one alkyne moiety produced adduct 207. Intramolecular addition of the intermediate 207 provided cyclic disulfide 208 then, dihydrothiepine 209 may form from disulfide 208 by loss of sulfur. 

Ethyl 9-mercapto-4-oxo-4//-pyrido[l, 2-a]pyrimidine-3-carboxylate 513 (R1 = COOEt, R2 = H) was also prepared from disulfide 136 in 54% yield (Scheme 31) (89EUP329126). 

The differences in antiwear properties of disulfides are related to their ability to be physisorbed about 100 to 1000 times faster than monosulfide on metal surfaces. The differences can be explained in terms of the lower energy needed for the formation of the same number of RS" ions from disulfides (Kajdas,1994). The exposed metal surface is extremely reactive to lubricant components, especially antiwear and extreme-pressure additives resulting the formation of a film on the contact surface. The reaction of emitted electrons of low energy (1 to 4 eV) with molecules of oil additives adsorbed on the friction surface may lead to formation of negative ions and negative ion radicals. The investigator (Kajdas, 1994 and 1985) pointed out the indispensability of the metal oxide film on the rubbing surface from the viewpoint of the theory of sulfide film formation. 

Metals. Lanthanide metals are also considered as valuable precursors. For example, alkoxides derived from cheap and low-boiling-point alcohols have been alternatively synthesized from metals in the presence of HgQ2 as catalyst [133]. Representative and specific methods of preparation include transmetalla-tion reactions (Eq. 7-9) [134], using ammonia solutions of ytterbium and europium as synthetic reagents (Eq. 10) [135] and the generation of thiolate complexes from disulfides (Eq. 11) [136],... 

They are also good soft electrophiles. Sulfenyl chlorides (RSC1) are easily made from disulfides (RS-SR) and sulfuryl chloride (SO2CI2). This S(VI) chloride has electrophilic chlorine atoms and is attacked by the nucleophilic disulfide to give two molecules of RSCl and gaseous SO2. There s a lot of sulfur chemistry here We start with a nucleophilic attack by one sulfur atom of the disulfide. 

Thiol-Based Reversible Chemistries From Disulfides to Thiazolidines... 

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