Butyltin bromides

The determination of the Concentrations in pyridine [N] which cause the coalescence of the signals of the diastereotopic groups of a 0.262 M solution methylneophyl-t-butyltin bromide (6) and of 0.332 M solution methylneophylphenyltin chloride (3) at 22 °C at respectively 60, 100 and 270 MHz shows12) that the k2 term is much smaller than the k3[N] term. From these results, it is clear that the inversion of the configuration of the metal atom of triorganotin halides is second-order in the nucleophile pyridine. An analogous rate equation has been found for the racemiza-tion of triorganosilicon halides 29), for which the activation entropy AS is about —50 e.u. Several mechanisms with increase of coordination number 30) can be proposed to account for this second order in the nucleophile 31) ... 

Tri-n-butyltin bromide (TBT), triethyltin bromide (TET), and trimethyltin chloride (TMT) inhibited the cardiac SR Ca uptake (Figure 4.1.2) and Ca +-ATPase (Figure 4.1.3) in vitro in rat heart in a concentration-dependent manner. The order of potency for Ca +-ATPase as determined by IC50, is TBT (2 pM) > TET (63 pM) > TMT (280 pM). For Ca uptake, it followed the same order, i.e., TBT (0.35 pM) > TET (10 pM) > TMT (440 pM). In agreement with them vifro results, both cardiac SR Ca +-ATPase and Ca uptake were significantly inhibited in vivo in rats treated with these organotin compounds... 

In this example, reaction solvent is evaporated and the tetradeutero-adamantane and tri-n-butyltin bromide dissolved in ether and washed with saturated KF in water (ca. 10 g in 100 ml). The resulting polymeric tri-n-butyltin fluoride is insoluble in both water and organic solvent and is removed by filtration under vacuum. The desired product is then purified by sublimation. 

Steinmeyer et al applied gas chromatography to the analysis of butyltin bromides. They showed that the butyltin bromides may be quantitatively converted to their more volatile butylmethyltin analog with methyl Grignard reagent and then determined by gas liquid chromatography with an estimated accuracy of about - 2%. Direct chromatography of the alkyltin bromides appeared to produce severe sample decomposition. The method is stated to be applicable to a number of tetralkyl and/or tetraryltins and alkyl or aryltin halides. 

Table 110. Factors to Convert Weight of Butylmethyltins to Weight of Butyltin Bromides...

Table 111. Prepared and Observed Compositions of Butyltin Bromide Standards... 

Prepared and Observed. Mole Per Cent Compositions Standards 1 and 2 of Butyltin Bromide ... 

The reaction of bromine with optically active sec-butyltin compounds Bu SnRs, to give sec-butyl bromide, can give retention or inversion in the sec-butyl group, depending on the natime of the group R... 

Allylboronates of type 103 react with equivalent amounts of aldoximes 102 (equation 73) giving allylhydroxylamines 104 in good yields. Similar reactions of aldoximes and glyoxylate oxime ethers with allyl bromide and indium also provide hydroxylamines. Additions of substituted allyl boronates to oximes produce mixtures of stereoisomers with ratio highly dependent on the steric size of substituents in both molecules. Addition of allyltri-n-butyltin to aldoxime ether 105 (equation 74) was found to proceed with a considerable diastereoselectivity. 

The above procedure is essentially that described previously by the author.2 Di-w-butylvinyltin has been prepared by the reaction between vinylmagnesium chloride with either di-w-butyltin dichloride or di-w-butyltin oxide.6 The preparation of vinylmagnesium bromide was first described by Normant.6... 

E. Vogel, H.-J. Altenbach, and D. Cremer, Angew. Chem., Int. Ed. Engl. 11,935 (1972). This paper also describes the conversion of bromide (5a) to parent 1,4-dioxocin by tri-n-butyltin hydride. 

Arylation of silyl enol ethers.1 Silyl enol ethers of methyl n- or sec-alkyl ketones undergo arylation when treated with an aryl bromide and tri-n-butyltin fluoride and a... 

Reduction of acyl chlorides to aldehydes,13 Tri-n-butyltin hydride reduces acyl chlorides to a mixture of aldehydes and esters. In the presence of a soluble Pd catalyst usually Pd[P(C6H5)3]4, only aldehydes obtain. This reduction is very general, and yields are usually > 80%. Reduction of double bonds is a minor competing reaction with a, / -unsaturatcd substrates (< 5% reduction). Of other reducible groups, only an allylic bromide group competes with the COC1 group. 

Monoetherification of polyols.12 Monobenzylation and monoallylation of polyols can be conducted conveniently under mild conditions by conversion to the stannylene derivative (dimeric) by di-n-butyltin oxide (5, 189 9, 141). The stannylene is then treated with benzyl bromide or allyl bromide and tetra-n-butylammonium iodide (1 equiv.) in benzene. The same conditions can be used to prepare monomethoxymethyl ethers. Quaternary ammonium bromides are less efficient catalysts than the iodides. These salts also accelerate reaction of stannylenes with acid anhydrides. The mechanism for this activation is not clear it may involve coordination of I" to tin. 

Lethality in mice was observed following single or repeated daily exposures to a butyltin mixture (81.2% tributyltin bromide and 3.7% dibutyltin dibromide) together with other unidentified compounds (15.1%) (Igarashi 1959). The concentration was 5.65 mgtin/m (1.16 ppm) as the butyltin mixture for different durations of exposure. The tributyltin bromide concentration was 1.1 ppm and that for dibutyltin bromide was 0.06 ppm. For a 2-day, 8-hour/day exposure, approximately 80%-90% of the exposed mice died. Despite the observation of other signs of toxicity (see Section 2.2.1.2) the exposure of the mice to multiple compounds confound the interpretation of the data. 

Dermal effects were observed during inhalation studies in mice that were exposed to a butyltin mixture (30 parts tributyltin bromide to 1 part dibutyltin bromide) and consisted of reddening of the skin and dilatation of the blood vessels of the nose, feet, and tail (Igarashi 1959). Inflamed eyes and nasal mucous membranes were observed in the last month of a 95-day inhalation study of tributyltin chloride in female rats (Gohlke et al. 1969). Concentrations of 4-6 mg/m (0.30-0.45 ppm) for 6 hours/day, 5 days/week were used. From these acute- and intermediate- duration studies with different compounds, the skin and eye irritation potential of organotins was demonstrated. 

Unger et al. [217] determined butyltins in non saline water by gas chromatography with flame photometric detection and confirmation by mass spectrometry. The sample was extracted with tropalone in //-hexane and organotin compounds derivatised with n-hexyl magnesium bromide to form tetraalkyltins. The n-hexyl derivatives of methyltin and butyltin species were easily separated and quantified relative to an internal standard (triphenyltin chloride) which was not found to be present in environmental samples and did not interfere. 

Pivaloyloxymethyl (Pom) esters are useful as prodrugs of penicillin and other 0-lactam antibiotics owing to their easy hydrolysis in vivo by ubiquitous non-specific esterases. Mascaretti and co-workers showed that Pom esters can also by cleaved under mild conditions with 2 equivalents of bis(tri-/i-butyltin)oxide as shown in Scheme 6.32. The intermediate tributylstannyl esters are readily hydrolysed on treatment with water to release the carboxylic acid. Functional groups such as aldehydes, thioacetals, amides, vinyl bromides, and nitro compounds are compatible.22... 

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