Silicon, thiol derivatives

Thiol derivatives of silicon, germanium, tin and lead can readily be prepared from a halide, usually chloride, and a thiol in the presence of a hydrogen halide acceptor or a metal thiolate. Various illustrative examples... 

The selection of a stationary phase suitable for the GC analysis of all amino acids seemed to be the main problem hindering the wider use of these derivatives, which were always applied to a limited number of amino acids only. For the separation of TFA-amyl esters about 100 stationary phases have been tested, most of which were rejected owing to the decomposition of the acyl derivatives of hydroxyl and thiol groups that proceeds on some stationary phases with Tyr, Ser, Hypro, Thr and CysH. The application of 25% DECS led to the elution of only eight derivatives of amino acids out of thirteen that were analysed [225], The polyester PEGA and the silicones QF-1 and MS-710 [197,227, 228] were reported as the most suitable liquid stationary phases. For the analysis of... 

R3MX are the most poisonous in the R4 MX (M = Sn, Pb) series this is also observed for the isostructural compounds of silicon . The toxic action of compounds of tin and lead is similar. Derivatives of R3MX inhibit oxidative phosphorylation, whereas R2MX2 binds thiol enzymes groups. Fungicidal activity of trialkylstannane R3MX derivatives is maximal when the number of carbon atoms is 9 in all three R substituents. On the whole, the toxicity of organic compounds of tin and lead decreases as the bulk of the substituents about the central metal atom increases. 

Silicon halides (especially the readily available chlorides) are probably the most synthetically useful and versatile monomeric inorganic silicon compounds. They may readily be reduced to hydrides, hydrolyzed to silanols (and subsequently to siloxanes), treated with other protic species such as alcohols, carboxylic acids, amines, and thiols to give SiA)R, Si-0C(0)R, Si NR2, and Si SR species respectively, used to make sUyl pseudohalogen derivatives by treatment with silver or alkali metal salts, for example, treated with sodium... 

Besides the halo-subsituted Z derivatives, the Msz group, a group that is based on the safety-catch principle, is of potential interest for particular synthetic tasks as it is stable toward acidic and basic reaction conditions, but it is readily cleaved in a one-pot procedure with silicon tetrachloride/TFA in the presence of scavengers such as anisole, phenols, sulfides, selenides, and thiols. 

Acylation of a simple thiol with an alkyl carboxylate is not a very suitable method for preparation of S-alkyl thiocarboxylates. Transesterification is, however, possible if either the thiol or the carboxylic ester is activated. The enhanced reactivity of boron, aluminum and silicon thiolates has been utilized for the synthesis of a large variety of thiocarboxylic S-esters, including hydroxy derivatives (from lactones). a,P-Unsaturated thiol esters, e.g. cinnamoyl or 2-butenoyl derivatives, are also accessible. Michael addition, an undesirable side reaction of thiols, is completely avoided if alkyl trimethylsilyl sulfides ortris(arylthio)boranes are applied. ... 

Photomechanical Responses of Azobenzene-Containing Materials. Ji et al. (2004) reported that a self-assembled monolayer (SAM) of azobenzene molecules on a silicon microcantilever created a photon-driven switch. Commercial silicon microcantilevers were electron-beam coated on one side with 3nm of primer layer (chromium), followed by 20 nm of gold. An azobenzene derivative with a decanthiol substituent on one ring was used to functionalize the gold surface. The thiol (-SH) end attached to the gold surface and the other azobenzene end disposed outward. 

While the majority of publications deal with thiols on gold, silanes on hydroxylated surfaces like silicon, glass, mica or ITO are important systems for many potential applications [3,55,67,68], although high quality SAMs of alkyltrichlorosilane derivatives are difficult to produce. SAMs of fatty acids are an important link between the LB and the self-assembly techniques [3]. 

Silylation is without a doubt the most employed derivation procedure today. It is particularly effective with alcohols, phenols, sugars, amines, thiols, steroids, and carboxylic acids. ° The reaction of an alcohol presented in Fignre 1.1 replaces an exchangeable hydrogen with a silicon. The operational conditions depend obviously on the analytes and the reagents used, but most silylation reactions are performed in an oven, at temperatures ranging from 60 to 80°C and with reaction times ranging from 20 to 30 minutes. 

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