Tributyltin bromide, reaction

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. 

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... 

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... 

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. 

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

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. 

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. 

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... 

The short Sanofi route to irbesartan (3) is outlined in Scheme 9.6. Dihydroimidazolone 27, which is prepared from the reaction of 1-amino-cyclopentanecarboxylic acid ester (25) with ethyl pentanimidate (26) in the presence of acetic acid in refluxing xylene, is alkylated with biphenylbenzyl bromide 18 in the presence of sodium hydride in DMF to give 28. Finally, the synthesis of irbesartan (3) is completed by the tetrazole formation from reaction of the nitrile group of 28 with tributyltin azide in refluxing xylene. [See Bernhart et al. (1993a, b).]... 

The seemingly complex imidazolone (78-3) is in fact obtained in a single step by reaction of the amino-ester (78-1) with the iminoether (78-2) derived from capro-nitrile. The relatively acidic proton on the heterocyclic ring is next removed by reaction with sodium hydride. This anion is then alkylated with the same biphenyl-methyl bromide (77-2) that was used to prepare losartan to afford (78-4). The nitrile group is in this case converted to the tetrazole by means of tributyltin azide, a reagent that involves milder conditions than the traditional acidic medium used to generate hydrazoic acid. Thus, treatment of (78-4) with the tin reagent affords irbesartan (75-5) [82]. 

Halobutyl)cyclobutanones form cyclooctanones when they are reduced with tributyltin hydride in the presence of 2,2 -azobisisobutyronitrile.3,5 216, 217 Iodides usually give better yields than bromides. It is essential to add the tin hydride reagent slowly over a period of several hours, to keep its concentration low and thus avoid side reactions. Examples are the reactions to give l,s 2,3 and 3.217 A further example is found in ref 216. 

To 244 mg (0.64 mmol) of the starting bromide (E/Z ratio 1 7) in dry toluene (0.015 M) under reflux was added 2.4 eq of tributyltin hydride and AIBN (catalytic amount) in 3 h through a syringe pump. The reaction mixture was cooled and the solvent was evaporated. The residue was dissolved in ether and 10% aqueous KF solution was added, and the mixture was stirred for 18 h. The organic phase was separated, dried, and evaporated. After flash chromatography (hexane-ethyl acetate, 90 10) of the residue gave the 134 mg (80%) of the product mp 75-77°C [a]D —61° (c 1.2, CHC13). Minor amounts of the noncyclized reduction product and the isomeric compound with an a-CHjCOjMe were also isolated. 

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