Aromatic with thiols

Various S-nucleophiles are allylated. Allylic acetates or carbonates react with thiols or trimethylsilyl sulfide (353) to give the allylic sulfide 354[222], Allyl sulfides are prepared by Pd-catalyzed allylic rearrangement of the dithio-carbonate 355 with elimination of COS under mild conditions. The benzyl alkyl sulfide 357 can be prepared from the dithiocarbonate 356 at 65 C[223,224], The allyl aryl sufide 359 is prepared by the reaction of an allylic carbonate with the aromatic thiol 358 by use of dppb under neutral condi-tions[225]. The O-allyl phosphoro- or phosphonothionate 360 undergoes the thiono thiolo allylic rearrangement (from 0-allyl to S -allyl rearrangement) to afford 361 and 362 at 130 C[226],... 

With Sulfur Nucleophiles N-Carboxy-protected aziridine-2-carboxylates react with thiols to give P-mercapto-ot-amino acid derivatives. The reaction is usually catalyzed by BF3 and the yields range from fair to excellent [15, 16, 108-111]. With N-unprotected 3-substituted aziridine-2-carboxylates, the ring-opening with thiols usually takes place with anti stereoselectivity, especially in the case of the C-3 aliphatic substituted substrates. In cases in which C-3 is aromatic, however, the stereoselectivity has been found to be a function of the substitution pattern on the aromatic ring 3-p-methoxy ph eri yl-su bs li In led aziridines 143a (Scheme 3.51) and... 

Thiols react more rapidly with nucleophilic radicals than with electrophilic radicals. They have very large Ctr with S and VAc, but near ideal transfer constants (C - 1.0) with acrylic monomers (Table 6.2). Aromatic thiols have higher C,r than aliphatic thiols but also give more retardation. This is a consequence of the poor reinitiation efficiency shown by the phenylthiyl radical. The substitution pattern of the alkanethiol appears to have only a small (<2-fokl) effect on the transfer constant. Studies on the reactions of small alkyl radicals with thiols indicate that the rate of the transfer reaction is accelerated in polar solvents and, in particular, water.5 Similar trends arc observed for transfer to 1 in S polymerization with Clr = 1.4 in benzene 3.6 in CUT and 6.1 in 5% aqueous CifiCN.1 In copolymerizations, the thiyl radicals react preferentially with electron-rich monomers (Section 3.4.3.2). 

Aromatic diazonium salts react easily in neutral aqueous solution with thiols such as N-acetylcysteine, forming compounds of the type Ar — N2 —S —CH2CH(NHAc) COOH. Nifontov et al. (1990) suggested that such compounds, e.g., that of 5-diazo-imidazole-4-carboxylate, function as a form of transport depot for cytotoxic diazo-carboxylate in the human body. 

Kobayashi, K., Kitagawa, S., and Ohtani, H., Development of capillary column packed with thiol-modified gold-coated polystyrene particles and its selectivity for aromatic compounds, J. Chromatogr. A, 1110, 95, 2006. 

LCEC systems are used for a wide variety of applications, many of which have been published [1,32]. Space does not permit a thorough review however, it is possible to generalize by considering the classes of compounds that have most frequently been studied phenols, aromatic amines, thiols, quinones, and nitro compounds. By analogy with liquid chromatography with UV detection (LCUV), it is frequently desirable to obtain an electrochemical spectrum of a compound to assess Its suitability for LCEC. Cyclic voltammetry (CV) is the electrochemical equivalent of spectroscopy (Chap. 3). It is useful to carry out CV experiments in several possible mobile phases, since electrochemical reactions can be very dependent on the medium. 

Chlorobenz[d]isothiazole-l, 1-dioxide ( pseudosaccharin chloride ) (6)3,24.25, lee, 25i, 26i, 262 displays the reactivity of a cyclic imidoyl chloride263 resembling very much carboxylic acid halides. In previous sections preparation of 3, 4, 5, 13, 68, 86, 89 from 6 has been mentioned. Derivatives of 6 substituted in the phenyl ring have been described.250 Interestingly, Meadow observed231 that crude 6 and material that contained phosphorus pentachloride reacted with thiols more readily than the pure compound. In the reaction of 6 with aromatic sulfonamides, aluminum chloride had been added for activation.252... 

Substituted aromatic thiols are oxidized by N-snUmylimides to yield equimolar mixtures of di- and trisulfanes (equation 45). This reaction proceeds via the intermediate adduct R NFl SO SR (7), which in favorable cases can be isolated (e.g. with R = 4-O2NC6H4). Compound (7) reacts with thiols according to equation (46), allowing the preparation of symmetrical disulfanes and unsymmetrical trisulfanes. 

From the reaction of the sodium salt of an aliphatic or aromatic mercaptan (thiol) with hexachlorocyclotriphospha-zatriene (1,3,5,2,4,6-triazatriphosphorine 2,2,4,4,6,6-hexa-... 

In the past 10 years other reductants of the C— Hg bond have been used, mainly thiols and sodium amalgam. Reduction with hydrogen sulfide, sodium dithionite, metals,alcohols, alkaline aqueous bases, aromatic amines, Wilkinson s catalyst and electrochemical reductions have also been described. Organomercurials react with thiols by free radical substitutions with an 5h2 mechanism (Scheme 34). The reaction between PhSH and A -hexenylmercury chloride initiated by light or AIBN gives a mixture of 1-hexene and methylcyclopentane. ... 

Very similar results to those described with propyne can be obtained with a wide variety of other alkynes, e. g., acetylene, higher aliphatic and aromatic alkynes as well as other nucleophilic reagents, such as water, aliphatic (primary, secondary, and tertiary) and aromatic alcohols, thiols, and amines. 

Aromatic chemicals are metabolized into unstable arene-oxides, which, as epoxides, are comparable to potentially equivalent electrophilic carbocations. These metabolites react easily with thiol groups derived from proteins, leading, for example, to hepatotoxicity. Bromobenzene seems to target a large group of functionally diverse hepatic proteins, as demonstrated recently in a proteomic analysis. The chemical is oxidized (Figure 33.10) into a 3,4-epoxide, which... 

Chemically, CS is a moderately reactive electrophile due to the presence of two electron-withdrawing nitrile groups attached to the olefinic bond. The site of reaction with nucleophiles is the olefinic carbon adjacent to the aromatic ring. Reactions are SN2-like, i.e. CS reacts with nucleophiles directly in a bimolecular fashion. CS reacts quite rapidly with water when in solution (half-life 14 min, 25°C, pH 7.4) to give 2-chlorobenzaldehyde and malonitrile. Reactions are much faster with thiols and amines. CS reacts rapidly with glutathione and plasma protein, although the reaction products have not been characterized (Cucinell et al., 1971). 

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