Trialkyl tin

A number of activated olefinic compounds react very weU in this scheme including methacrylates, crotonates, acrylonitrile, and vinyl ketones. These reactions are typicaHy mn in an etherial solvent and can be mn without the complications of undesirable side reactions leading to trialkylated tin species. 

A useful synthesis of allylstannanes from primary alcohols involves conversion of the alcohols into their O-substituted 5-methyl carbonodithioates, thermolysis to effect [3,3] rearrangement to the corresponding 5-substituted 5-methyl carbonodithioates, and treatment with a trialkyl-tin hydride under free-radical conditions to form the allylstannane21. This procedure has been applied to the synthesis of functionalized allylstannanes including (5)-( )-4-(benzyloxy)-2-pen-tenyl(tributyl)stannane22. 

It seems that this anionic exchange would be relevant also to explain interactions of trialkyl tin (TAT) compounds (TET, tripropyltin chloride, TBT chloride) with the mitochondria. The current view of this phenomenon is that these compounds, by exploiting the Cl and OH gradient in energized mitochondria, behave as electroneutral OH /Cl exchangers. The crucial point of this new mechanism is that TATs enter the mitochondria as lipophilic cations [RsSn (rV)] and not as electroneutral compounds. The influx is followed by extrusion of the TAT compounds as electroneutral hydroxy compounds RsSnOH. ... 

Barnes JM, Stoner HB (1958) Toxic properties of some dialkyl and trialkyl tin salts. British Journaiof industriai Medicine, 15 15-22. 

Aldridge, W.N. and Street, B.W. (1964). Oxidative phosphorylation biochemical effects and properties of trialkyl tin. Biochemical Journal 91, 287-297. 

Besides the silyl enolate-mediated aldol reactions, organotin(IY) enolates are also versatile nucleophiles toward various aldehydes in the absence or presence of Lewis acid.60 However, this reaction requires a stoichiometric amount of the toxic trialkyl tin compound, which may limit its application. Yanagisawa et al.61 found that in the presence of one equivalent of methanol, the aldol reaction of an aldehyde with a cyclohexenol trichloroacetate proceeds readily at 20°C, providing the aldol product with more than 70% yield. They thus carried out the asymmetric version of this reaction using a BINAP silver(I) complex as chiral catalyst (Scheme 3-34). As shown in Table 3-8, the Sn(IY)-mediated aldol reaction results in a good diastereoselectivity (,anti/syn ratio) and also high enantioselectivity for the major component. 

The presence of any residual trialkyl tin groups in the final matrix is not desirable in the context of catalysis. Tin is a catalytically active metal and thus could compHcate and potentially interfere with reactions of other active metals in the matrix. Fortunately we found that all residual tin groups in these matrices can be replaced with tiimethyl-silyl (TMS) groups simply by exposure to TMSCl in the gas phase. This observation also indicates that none of these sites becomes inaccessible to further reaction when crosslinking in the matrix is appropriately adjusted. 

If it is assumed that the crosslinking reaction proceeds as illustrated in Equation 4.2, every time a link is formed a trialkyl tin chloride byproduct is released from the matrix. Given that the precise number of tin groups and amounts of linking reagents are known at the beginning of each dose then, in a stepwise manner, it... 

This approach involves additions of alkyl radicals to C=N bonds and snbseqnent fi-expulsion of the phenylsulfonyl group (as a radical) which react with bis(trialkyl)tin to propagate a chain. The phenylsulfonyl group lowers the energy of the LUMO of the radical acceptor, increasing the rate of addition of alkyl radicals . 

Hence, most photochemical precursors of radicals in solution (peroxides, azo compounds, most halides, etc.) are not generally suitable for in situ generation of these species in confined environments such as matrices (of course reagents that generate radicals by abstraction, such as the popular trialkyl tin hydrides, are also excluded from matrix isolation). 

Of all the radical reactions, the exo-l,5-cycIization of a hex-5-enyl radical to cyclopen-tylmethyl radical and its subsequent trapping by various reagents have attracted the most attention from synthetic chemists (Scheme 1) [4-7]. Starting materials that are most often used for the tin method (initiation of the chain by trialkyl tin radical) are halides, sulfides, selenides, or thionocarbonates. The generation and cyclization of the radical proceeds under exceptionally mild neutral conditions, and these conditions are compatible with a wide variety of common functional groups. A prototypical example of an application in carbohydrate chemistry is shown in Scheme 2 [8]. Readily available 2,3-di-O-isopropyl-ideneribonolactone 1 was converted into the bromoacrylate 2 in three steps. Radical... 

Two other systematic solution phase tritium isotope effects studies have been made that will only be mentioned here. In the reduction of alkyl halides by trialkyl-tin hydrides, there is an abstraction step... 

Exposure to neurotoxicants or neurotoxic chemical substances causes severe adverse health effects to the nervous system, which is very sensitive to organometallic compounds and sulfide compounds. These compounds disrupt the normal functioning of the central nervous system, peripheral nerves or sensory organs, and the conduction of nerve impulses. Thus, chemical substances are considered neurotoxicants when they induce a consistent pattern of neural dysfunction. The chemical substances include but are not limited to carbon disulfide, manganese, methyl mercury, organic phosphorous insecticides, tetraethyl lead, thallium, and trialkyl tin compounds. 

Trialkyl tin lithium compounds are prepared following the same procedure as for triphenyltin lithium , Tri-n-butyltin lithium and triethyltin lithium are prepared by... 

Trimethylsiloxy)-l,3,2-dioxaborolans and -borinans are formed by cleavage of corresponding trialkyl-tin or -germanium derivatives by... 

Stannylsulfonamides can also be prepared by the addition of the SnO bond to sulfo-diimides (RN=S=NR) or sulfinylamines (RN=S=0) in these reactions, the bis(trialkyl-tin) oxides appear to be more reactive than the corresponding alkoxides.62-63 The weak sulfur-containing acceptors can then be displaced by more powerful acceptors such as isocyanates or chloral. 

Several chemo-selective aryl-aryl coupling reactions of aromatic halides and organometallics with transition-metal catalysts are known.16 For example, coupling reactions of arylboronic acids with aryl halides with Pd(0) catalyst,17 arylmagnesium halides with aryl halides with Ni(II) catalysts,18 and aryl trialkyl tin compounds with aryl halides with Pd(0) catalyst19 are well known. The polyhalo-aromatic substances were converted into AB -type monomers by selective metallation of one of the halo-functional groups in each monomer. 

One of the most thoroughly studied endocrine disrupters is tributyl tin (TBT).Trialkyl tin formulations (e.g. as the chloride salt Fig. 7.12) were widely used in... 

This procedure illustrates the bromopropylation of an alcohol by allylation and then hydroboration/bromination,7 a clean, selective procedure compared with other approaches via 3-substituted propyl bromide derivatives. Conversion to the tetraalkyl tin, then brominative cleavage, is the standard sequence for preparation of trialkyl tin derivatives.8 The standard lithium aluminum hydride (UAIH4) reduction of the tin bromide was not usable here because of contamination of the product by UAIH4 byproducts that were not easily separated, and the polymethylhydrosiloxane reduction method9 was not successful. However, use of NaBH4 in f, 2-dimethoxyethane was effective and convenient.10... 

Analogous reactions afford other compounds of the type R3SnR, such as alkyl(tri(cycloalkyl)]tin,408 alkyl(triphenyl)tin,409 alkenyl-(trialkyl)tin and -(tri-aryl)tin,398,410 and alkynyl(triaryl)tin compounds 411 also compounds of the general formula R2SnR 2, such as dialkyl- and diaryl-bis(perfluorovinyl)-tin412 and dialkynyl(diaryl)tin compounds.413... 

The applications of organometallic agents in technology show every promise of increasing. The traditional use of tetraethyllead in motor fuels may eventurlly be replaced by some other type. Tin alkyls have gained some recent prominence both for the biocidal properties of certain trialkyl-tin derivatives and for the ultraviolet-discoloration protection offered vinyl plastics by dibutyltin dilaurate. Also attention should be drawn to the possi-... 

One of the earliest techniques for preparation of (PhLi)Cr(CO)3 is the reaction of diphenylmercury bis-Cr(CO)3 with n-BuLi [17]. Quenching with CO2 gave the benzoic acid complex in 50% yield. Analogously, a lithium derivative can be obtained from trialkyl tin compound (3) via transmetallation with n-BuLi. The resulting anion was quenched with a variety of electrophiles with retention of stereochemistry [18]. 

It is interesting to note that the same reaction catalyzed by palladium pincer complex can also be carried out using aUylstaimane derivatives [38]. A dear advantage of the above procedure (Figure 4.8) is that it does not require a tedious trialkyl tin prefunctionaHzation of the allylnitrile derivatives. 

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