Subject thiolate

Greaney and coworkers have introduced the conjugate addition of thiols to Michael acceptors as an effective adaptive DCL strategy [46,47]. The reaction is well suited for biological DCL synthesis, taking place in water with no requirement for external reagents. As with disulfide bond formation, the reaction is subject to simple and effective pH control. Under mildly basic conditions, the thiolate anion adds rapidly to Michael acceptors under equilibrium conditions. Acidification effectively switches the reaction... 

Reactions of thiolates with chlorocyclophosphazenes are found to proceed in a geminal pathway. Only very limited thiols such as thiophenol, methyl and ethyl mercaptans have been subjected to these studies (Eq. 24) [80, 81]. 

Sodium tetrathionate (Na2S406) is a redox compound that under the right conditions can facilitate the formation of disulfide bonds from free sulfhydryls. The tetrathionate anion reacts with a sulfhydryl to create a somewhat stable active intermediate, a sulfenylthiosulfate (Fig. 102). Upon attack of the nucleophilic thiolate anion on this activated species, the thiosulfate (S203 =) leaving group is removed and a disulfide linkage forms (Pihl and Lange, 1962). The reduction of tetrathionate to thiosulfate in vivo was a subject of early study (Theis and Freeland, 1940 Chen et al., 1934). 

Among these groups (siloxy, amino, benzotriazolyl, thiolate, cyanide) the methoxy group has been the subject of a large number of studies. To generate the azomethine ylid, essentialy three reagents have been utilized silyl triflate (or iodide), trifluoroacetic acid and lithium fluoride (sometime combined with sonication). Thermal rearrangement has also proven to be efficient. 

DeVries et al.224 demonstrated experimentally that polar singularities form when a curved surface is coated with ordered monolayers (hairy-ball-theorem). The thiolates bound at the polar positions exchange faster than those in the bulk monolayer, thus allowing introduction of two—and only two—functional groups at the poles of a nanoparticle.224 This was the first example of divalent metal nanoparticles. This discovery opens up the path to new applications in the field of materials chemistry, and supramolecular chemistry, as stressed by Perepichka and Rosei.225 Undoubtedly, the regiochemical stability of these disubstituted nanoparticles and the chemical yield of their functionalization should be the subject of future studies. 

The synthesis of the derivatives (339)-(346) was carried out as shown in Scheme 28. Metalation of the acetal (336), followed by thiolation and alkylation, gave the ester derivative (337). Acetal deprotection to form (338) and subsequent treatment under Knoevenagel conditions with piper-idinium acetate in benzene afforded the desired ester (339). Reduction of compound (339) gave alcohol (340), which was converted to aldehyde (341) and protected as its acetal (342) under standard conditions. Deprotonation was effected by Bu"Li in THF at — 78 °C and subsequent conversion to the sulfonyl chloride was carried out by sequential treatment with sulfur dioxide and A-chloro-succinimide. Treatment of the sulfonyl chloride (343) with concentrated NH4OH in acetone provided the sulfonamide (344), which was deprotected (345) and subjected to reductive amination to provide compounds in the aminomethyl sulfonamide series (346). 

The SRN1 subject has already been reviewed [4,107, 108,109,110, 111] and the large variety of the used anions (carbanions, nitronates, thiolates, enolates, anions of group V etc... ) with several electron accepting substrates (chloron-itro- or dinitro- compounds, dimethylsulfoxide, organic halides, etc.. . ) was... 

The bridging chloride ligands in these [Ir(olefin)2Cl]2 compounds are susceptible to metathesis reactions, yielding new dimeric compounds of the form [Ir(olefin)2B]2 where B represents a new bridging ligand. AUcoxides, thiolates, and carboxylates have all been employed successfully in the replacement of chloride. The complexes with B = Br, I have also been prepared, both by metathesis reactions and by direct reaction of cyclooctene or cyclooctadiene with IrBrs or Iris The olefin complexes also provide excellent starting materials for the syntheses of arene and cyclopentadienyl iridium complexes, a subject that will be discussed in the next section. 

Hydroxy-4-cyano-l,2,5-thiadiazole 22 was subjected to thiocarbamoy-lation and subsequent thermal rearrangement for the production of the nitrile intermediate, which upon hydrolysis gave 3-thiolate-4-amide-1,2,5-thiadiazole 25 (Scheme 16) [50],... 

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