Trialkyltin chlorides

Reactions of trifluorovinyllithium with a variety of electrophiles such as proton, halogen, trialkylsilyl chloride, trialkyltin chloride, methyl iodide, carbon dioxide, sulfur dioxide afforded the corresponding trifluorovinylated derivatives [111, 113,114] (Scheme41). 

Unbranched and substituted alkyl carbamates, such as 146 or 147 [62,88] do not cause any problems in the deprotonation step. Deuteration (with CH3OD or dissolved CH3CO2D), methoxycarbonylation (gaseous CO2, followed by diazomethane after work-up or methyl chloroformate), alkylation with methyl iodide, substitution with trialkylsilyl chlorides, trialkyltin chlorides and even tri-methyllead bromide, addition onto aldehydes and ketones, and acylation with acid chlorides or esters, all proceed without difficulties. Although a ketone is formed in the latter reactions, which is at least 15 orders of magnitude thermodynamically more acidic than the alkyl carbamate we never observed enolate formation, racemization or epimerization - with one exception it occurred to some extent after formylation with formate esters [79]. 

Smith [117] discussed the determination of tin in water. In the determination of low concentrations of the order of 40 ng of trialkyltin chlorides in sea water it has been observed that these compounds are very volatile and are easily lost upon evaporation with acid. Quantitative recovery of tin is, however, obtained in the absence of chloride ion during evaporation with acid. Preliminary removal of chlorides from sea water by passage down a column of IRA 400 resin before digestion with acid completely overcame loss of tin on subsequent evaporation, with acid giving a tin recovery of 90%. 

Another synthetic route which gives a good yield of the labelled tin hydride involves the hydrolysis of an organometallic intermediate such as a trialkylstannyllithium46 with deuterated or tritiated water. The trialkylstannyllithium can be prepared by treating the trialkyltin chloride with lithium metal in THF46. This process is shown in equation 42. 

Snoeij, N.J., A.A.J. Van Iersel, A.H. Penninks, and W. Seinen. 1985. Toxicity of triorganotin compounds comparative in vivo studies with a series of trialkyltin compounds and triphenyltin chloride in male rats. Toxicol. Appl. Pharmacol. 81 2 4-286. 

Electrophiles, which lead to high yields, are methyl iodide, trialkyltin- and trialkylsUyl chlorides, diphenylphosphinyl chloride, acid chlorides, aldehydes and carbon dioxide. Remarkably, though highly acidic ketones are formed on acylation, no deprotonation or racemization by excess of carbanionic species occurs. Other alkyl halides than methyl iodide react very sluggishly with low yields. Benzylic and aUylic halides lead to partial racemization, presumably due to single-electron transfer (SET) in the alkylation step. As very recently found by Papillon and Taylor, racemization of 42 can be suppressed by copper-zinc-lithium exchange before alkylation to 43 via the Knochel cuprates (equation 7) °. 

The trialkyl(trifluoromethyl)tin can also be prepared via the reaction of triphenylphosphine and dibromodifluoromethane followed by the treatment with potassium fluoride and trialkyltin chloride [104,105] (Scheme 37). 

Conversion of allylic acetates of allylstannanes by treatment with Et2AlSnBus and Pd° catalysts proceeds by addition of the tin to the metal, followed by reductive elimination (equation 204).309 The corresponding ally phosphonate, however, showed some loss of stereochemical integrity (equation 205).310 The Pd°-catalyzed reaction of allylic acetates, trialkyltin chlorides and Smh produced allylstannanes with no stereospecificity.311... 

Although no coordination complexes of tetraalkyltins with nucleophiles (i.e. Lewis bases) have been reported, it is known that trialkyltin chlorides can form coordination complexes with various Lewis bases. Bolles and Drago38 have shown that trimethyltin chloride forms 1 1 complexes with bases such as acetone, acetonitrile, dimethylsulphoxide, and pyridine. All of these complexes are formed exothermally (in inert solvents such as CC14), with values of Af/299 ranging from —4.8 to —8.2 kcal.mole-1 for the reaction... 

A more detailed study (50) of the 119Sn chemical shifts of trimethyl-and triethyl-tin chloride as a function of concentration and temperature in various polar solvents has revealed the effect of complexing on chemical shift. The formation of a 1 1 complex of trialkyltin chloride in a polar donor solvent, L, may be written as ... 

Pyridylstannanes are accessed by transmetallation of pyridyllithium reagents with trialkyltin halides such as tributyltin chloride <20000L3373, 1998JA2805> and typically utilized as coupling partners in Stille reactions with... 

Most recently, Wang and Chu125) have reported that trialkyltin chloride can be used to induce selective migration of a primary alkyl group from boron atom to the adjacent acetylenic carbon atom of lithium 1-alkynyltrialkylboranes. Protonolysis of the resultant olefinic intermediates provides the corresponding (Z)-alkenes. 

The lithium salts of acyclic secondary amines 92 can be conveniently transformed into the corresponding carbamoyllithiums 89 at —78 °C. Under these reaction conditions they react with trialkyltin chlorides to give carbamoyl stannanes 93 (Scheme 24)98. In the case of benzyl and allyl halides, an alkylation can occur affording products 94. However, when trialkylsilyl chlorides were used as electrophiles no carbamoyl silanes could be detected.. V-Alkyl thiocarbamates 95 can be prepared by reaction of the same intermediates 89 with sulfur followed by. S -alkylation at 0°C (Scheme 24)". 

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