Tributyltin bromide

In a 50 ml flask fitted with a reflux condenser 5.5 g (0.0189 mol) of tributylstannane (tributyltin hydride) is added to 3.5g (0.018mol) of octyl bromide. An exothermic reaction ensues. Cooling is applied if the temperature rises above 50°. After 1 hour the mixture is distilled, giving 80% yield of octane and 90% yield of tributyltin bromide. 

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. 

Rats were exposed to a nominal concentration of 2 mg tin/m (0.41 ppm) as a mixture of tributyltin bromide (81.2%) with other compounds such as dibutyltin dibromide in acute- and intermediate-duration exposures to assess reproductive effects (Iwamoto 1960). This tin exposure was equivalent to 0.39 ppm tributyltin bromide and 0.02 ppm dibutyltin bromide. Pregnancy rates were markedly reduced after 4 weeks to 3 months of exposure however, at least partial reversibility of the effects was seen when exposure was discontinued. Histopathological evaluations were made... 

Tributyltin bromide or iodide and dibutyltin dibromide or diiodide can be prepared from the corresponding chlorides by reaction with alkyl bromides or iodides in the presence of a tetrabutylammonium halide catalyst. It is suggested that the reaction involves the coordination of halide ion to the tin, then nucleophilic substitution by the chloride ligand at the carbon centre (equations 11-18,11-19 and 11-20).35... 

This gives us the tributyltin bromide product and a primary carbon radical with which to do an intramolecular radical addition to a pi bond. 

Small amounts of tributyltin bromide and butyltin tribromide also form (Figure 1). 

The molar loss of tin tetrabromide and tetrabutyltin is equaled by the gain of butyltin tribromide and tributyltin bromide. What is occurring is the room temperature reaction of equal molar amounts of tin tetrabromide and tetrabutyltin to form butyltin tribromide and tributyltin bromide prior to reaction with the Grignard reagent. Standards 3 through 6 wefe made to contain minimal amounts of either tin tetrabromide or tetrabutyltin and the agreement between observed and added concentrations is much better, (Table 111) but even here the observed values for tin tetrabromide and tetrabutyltin are consistently low and the observed values for butyltin tribromide and tributyltin bromide consistently high. 

Radical cyclization reactions are not particularly popular, owing in part to the lack of specificity often observed, so it is interesting to note that the cyclization shown in Scheme 22 proceeds in up to 90% yield when a polymer-supported organotin reagent is used. Lower yields result from the use of BusSnH, and this is attributed to the purification procedure that is necessary to remove the tributyltin bromide at the end of the reaction. 

The allylstannane 474 is prepared by the reaction of allylic acetates or phosphates with tributyltin chloride and Sml2[286,308] or electroreduction[309]. Bu-iSnAlEt2 prepared in situ is used for the preparation of the allylstannane 475. These reactions correspond to inversion of an allyl cation to an allyl anion[3l0. 311], The reaction has been applied to the reductive cyclization of the alkenyl bromide in 476 with the allylic acetate to yield 477[312]. Intramolecular coupling of the allylic acetate in 478 with aryl bromide proceeds using BuiSnAlEti (479) by in situ formation of the allylstannane 480 and its reaction with the aryl bromide via transmetallation. (Another mechanistic possibility is the formation of an arylstannane and its coupling with allylic... 

Tributyl(l-ethoxy-2-propenyl)stannane (2) was first prepared from tributyl[chloro(ethoxy)-methyl]stannane and vinylmagnesium bromide, and found to be unstable with respect to 1,3-migration of the tributyltin substituent101. Tributyl(l-ethoxy-3-methyl-2-butenyl)stannane (1) was found to be more stable, and has since been prepared directly from (tributyl)(diethoxy-methyl)stannane and 2-methylpropenylaluminum dichloride generated in situ102. 

Quebrachitol was converted into iL-c/j/roinositol (105). Exhaustive O-isopropylidenation of 105 with 2,2-dimethoxypropane, selective removal of the 3,4-0-protective group, and preferential 3-0-benzylation gave compound 106. Oxidation of 106 with dimethyl sulfoxide-oxalyl chloride provided the inosose 107. Wittig reaction of 107 with methyl(triphenyl)phos-phonium bromide and butyllithium, and subsequent hydroboration and oxidation furnished compound 108. A series of reactions, namely, protection of the primary hydroxyl group, 0-debenzylation, formation of A-methyl dithiocarbonate, deoxygenation with tributyltin hydride, and removal of the protective groups, converted 108 into 7. 

Helium MIP-MS is also a very sensitive detection system for organotin compounds, such as tetraethyltin (TET), tetrabutyltin (TBT), triethyltin bromide (TET-Br), tripropyltin chloride (TPT-C1), tributyltin chloride (TBT-C1), and others, separated by CGC [213]. Detection limits at sub-pg levels were achieved, and linear dynamic ranges of at least three orders of magnitude were obtained. 

Tributyltin isocyanate 61 treated by phenylmagnesium bromide gives tributylphenyltin 62 in 100% yield. Reagent 61 is prepared140 by reaction of BusSnH with... 

Tributyltin-124 bromide has been prepared in a yield of 80% by reacting tetrabutyltin-124 in anhydrous methanol with one equivalent of bromine (equation 31). 

Other workers have also made tributyltin-113 labelled compounds for environmental and metabolic studies. For instance, Brown and coworkers37 prepared bis(tributyltin-l 13) oxide by first refluxing tin-113, which was produced by neutron irradiation of metallic tin, in a bromine-chloroform solution for four hours. The resulting tin-113 tetrabromide was subsequently converted into tributyltin-113 bromide by reaction with three equivalents of unlabelled tetrabutyltin for four hours at 220 °C. The bis(tributyltin-113) oxide was finally obtained by hydrolysing the tributyltin-113 bromide with a KOH-95% ethanol solution... 

Aryl halides can also be reduced by tin hydrides76,77, although these reactions always require initiators because the stronger C—X bonds in aryl halides are less reactive than the C—X bonds in alkyl halides. In fact, a series of meta- and para-substituted bromobenzenes, where X is either meta- or para-CH3O-, C=N, Cl, F, CF3, CH3, Bu-f or 2,6-dichloro, have been reduced by tributyltin deuteride (equation 60). It is worth noting that the more reactive bromide is reduced selectively in the presence of the less reactive chloride and fluoride groups (equation 61). 

Preparation. The reagent can be prepared in 94% yield by the reaction of allylmagnesium bromide with bis(tributyltin) oxide in ether. Sonication is useful for initiation of the Grignard reaction. 

Radical homologation. This tin pinacolate is known to generate trimethyltin radicals at 60° and appears to be superior to tributyltin hydride as a source of stannyl radicals for addition of alkyl halides to O-benzylformaldoxime (equation I).1 Iodides, bromides, and selenides can be used as radical precursors. The same... 

Muller [76] has described a gas chromatographic method for the determination of tributyltin compounds in sediments. The tributyltin compounds are first converted to tributylmethyltin by reaction with ethyl magnesium bromide, and then analysed using capillary gas chromatography with flame photometric detection and gas chromatography-mass spectrometry. Tributyltin was found in samples of sediment and these results demonstrated that the technique has detection limits of less than 0.5pg L 1. 

Allenyl ethers are useful key building blocks for the synthesis of a-methylene-y-butyrolactones [129, 130], The synthesis of the antileukemic botryodiplodin was accomplished with the crucial steps briefly presented in Scheme 8.56. Bromoallenyl ethers 225 were easily prepared by base-induced isomerization from the corresponding /3-bromoalkyl alkynyl ether compounds and then subjected to electrophilic bro-mination with NBS. The resulting acetals 226 were converted into 2-alkoxy-3-methy-lenetetrahydrofurans 227 by dehydrohalogenation of the alkenyl bromide unit to an alkyne and subsequent radical cyclization employing tributyltin hydride [130],... 

The silylated tin compound 199, obtained from tributyltin hydride and N-bis(trimethylsilyl)propargylamine (198) in the presence of a trace of AIBN (2,2/-azobisisobutyronitrile), is a versatile reagent for the preparation of allylic amines. Treatment with aryl bromides ArBr (Ar = Ph, 4-MeOCgH4, 4-O2NC6H4 etc.) under Pd(PPh3)4 catalysis yields the silylated amines 200, which are hydrolysed by acids to the free amines 201. 199 is converted into the lithium compound 202, which is transformed into 203 by aqueous ammonium chloride and into 204 by the action of alkyl halides RX (R = Me, Et or allyl) (equation 76)204. 

Crich and Rumthao reported a new synthesis of carbazomycin B using a benzeneselenol-catalyzed, stannane-mediated addition of an aryl radical to the functionalized iodocarbamate 835, followed by cyclization and dehydrogenative aromatization (622). The iodocarbamate 835 required for the key radical reaction was obtained from the nitrophenol 784 (609) (see Scheme 5.85). lodination of 784, followed by acetylation, afforded 3,4-dimethyl-6-iodo-2-methoxy-5-nitrophenyl acetate 834. Reduction of 834 with iron and ferric chloride in acetic acid, followed by reaction with methyl chloroformate, led to the iodocarbamate 835. Reaction of 835 and diphenyl diselenide in refluxing benzene with tributyltin hydride and azobisisobutyronitrile (AIBN) gave the adduct 836 in 40% yield, along with 8% of the recovered substrate and 12% of the deiodinated carbamate 837. Treatment of 836 with phenylselenenyl bromide in dichloromethane afforded the phenylselenenyltetrahydrocarbazole 838. Oxidative... 

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