Trialkyl tin compounds

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. 

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. 

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 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]. 

This agrees with other evidence, which confirms the instability of nitrogen base adducts of triphenyltin derivatives, and distinguishes such derivatives from trialkyl tin compounds. This difference is clearly important in interpreting the interactions which can occur between R Sn groups and anions such as C10 , BF " etc. on the one hand, and between R Sn group and nitrogen bases on the other. The possible nature of these interactions is then examined with reference to the use of filled 4d and unfilled 5d orbitals on the tin atom. 

The small amount of tin found in canned foods is quite harmless. The agreed limit of tin content in U.S. foods is 300 mg/kg. The trialkyl and triaryl tin compounds are used as biocides and must be handled carefully. 

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. 

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. ... 

Two important classes of reactions use labelled tin compounds to prepare labelled compounds for mechanistic and analytical purposes. In the first type of reaction, labelled trialkyl- or triaryl tin hydrides (stannanes) are used to reduce (replace) several different groups such as halogen, —N02, —N=C, —N=C=Se, —COOR, —SR or an acetal group with a deuterium or a tritium atom. 

Tin is comparable in its toxicological behavior to lead and mercury. Bivalent tin compounds generally are more toxic than the tetravalent compounds. Furthermore, organic tin compounds are more toxic than inorganic ones and the trialkyl analogs (triethyltin, trimethyltin, tributyltin) are the most toxic. As the number of carbon atoms attached to tin increases, the toxicity of the organic tin compounds rapidly declines9,77. 

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). 

Trlazoles of the type (440) are useful for regulating local plant growth (8iMiP4iloo). Trialkyl(l,2,3-triazolyl)tin compounds (441) can be used as biocides (81GEP293695i). 

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

HaIo- and l,l-Dihaloalkyl(trialkyl)metal Compounds (Metal = Silicon, Tin)... 

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... 

Terminal acetylenes RC=CH, however, yield trialkyl(alkynyl)tin compounds on reaction with trialkyltin amides456 or alkoxides457 or with trialkyltin hydroxides458 or bis(trialkyltin) oxides 459... 

Trialkyl tin and triphenyl tin compounds Butyltin chlorides Butyl phenyl and cyclohexyl tin compounds... 

Trialkyltin and triaryltin compounds possess powerful biocidal properties. These are manifested to a high degree only when the tin atom is combined directly with three carbon atoms, as in trialkyl compounds (R3SnX) biocidal effects are at a maximum when the total number of carbon atoms attached to Sn is 12. These compounds are used as fungicides, insecticides and as pest control in agricultural applications29. 

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