Displacement by thiol

Near monodisperse Au NPs in the size range of 1—4nm can be obtained using dodecylthioether end-functionalized PMMA as stabilizer. Particle size is controlled by varying the concentration of the stabilizing polymer, which can be readily displaced by thiol ligands to yield MPCs of the usual type [97]. 

The toxic forms of arsenic are mainly (Section III,A) compounds of the type R—AsX2, where X is a ligand that is easily displaced by thiols. Many such compounds are volatile, and this increases their hazard. As mentioned in Section VII,A,2, one such compound, Cl2As— CH2—AsC12, is a convenient intermediate in the synthesis of the diphosphate analogue H203As—CH2—As03H2. Obviously, its distillation and that of any similar compound should be performed in a fume... 

The catalytic action of a metal complex thus depends on the stability and solubility of the complex present in the reactant solutions. Provided that the coordination atmosphere of a metal ion is not displaced by thiol entities, the nature of the ligand affects the rate of electron transfer and the kinetics of the over-all oxidation. 

The brominated chelates are chemically much less reactive than the organic ligands themselves. Most nucleophilic substitution reactions are ineffective, but bromine can be displaced by thiols (equation 57).280 The halo complexes do not react with lithium or magnesium metals, but can be hydrogenolyzed to the unsubstituted complexes (equation 58).281... 

While the fluoro group in 4-fluoroimidazoles is stable in the presence of nucleophiles, a 2-fluoro group is labile under fairly mild conditions. The ease of displacement by thiol is doubtless due to the intermediate formation of the symmetrical 2-fluoroimidazolium cation (125) which is subject to addition-elimination processes (Scheme 58) (80AHC(27)241, B-76MI40701). 

It is possible to characterise P-Au-N linkages by P and NMR in solution and in the solid state by the observation of two-bond P- N couplings The EtjPAuN(imido) complexes that we have studied (for the imides phthalhnide, saccharin, S,S-diphenylhydantoin and riboflavin) themselves exhibit good anti-inflammatory activity. The imido ligand is readily displaced by thiols. ... 

Aminosodium salt and acylated with 1 H-tetrazole-1 -acetyl chloride. The acetoxy group is then displaced by reaction with 5-methyl-1,3-4-thi-adiazole-2-thiol in buffer solution. The product acid is converted to the sodium salt by NaHCOa. 

The cyclopentadienyl groups are readily displaced by protic acids HX (e.g., alcohols, phenols, thiols, and oximes), providing a convenient route to other Sn(II) compounds (320-323). 

The halogen in 5-bromofuran-2-carboxaldehyde is readily displaced by aromatic thiols, and the aromatic residue can be provided by pyridazine, benzeneselenazole, benzimidazole, benzoxazole, etc. as well as benzene.181... 

Compound 26, likewise, undergoes a series of displacement reactions (Scheme 34). Whereas reaction with copper(I) cyanide replaces only one chlorine atom to yield 136, all are displaced by reactions with ammonia and isopropylamine, diethyl(trimethylsilyl)amine, water, and thiols to give, respectively, 137-140. Some additional transformations are also shown. 

In much the same vein, nitration of 2,3-dimethylpyridine Al-oxide (49-1) affords the nitro derivative (49-2). The newly introduced nitro group is then displaced by the aUcoxide from 3-methoxypropanol to afford the corresponding ether (49-3). Proceeding much as above, the methyl group at the position adj acent to the nitrogen is converted to its chloride (49-5). Condensation with benzimidazol-2-thiol then affords rabeprazole (49-6) [52]. 

A wide range of iron compounds catalyze the indene-thiophenol co-oxidation reaction—e.g., FeCl3 and a variety of complexes formed by chelation. Differences in their behavior are believed to be correlated approximately with the ease of displacement of ligands by thiols or with their susceptibility to attack by peroxide, but the lack of reproducibility which has made much of this work extremely tedious makes quantitative deductions difficult. 

The corresponding reactions are mostly ionic involving nucleophilic displacement by SnI, Sn2 or carbonyl substitution with amines, alcohols and thiols on carbon electrophiles. The normal polarity of the disconnection 1 will be a cationic carbon synthon 2 and an anionic heteroatom synthon 3 represented by acyl or alkyl halides 4 as electrophiles and amines, alcohol or thiols 5 as nucleophiles. 

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