Reagents tributyltin hydride

One Te-C bond in a diorgano tellurium can be cleaved by alkali metals, organic lithium compounds, sodium hydroxide, lithium aluminum hydride, sodium borohydride, Grignard reagents, tributyltin hydride, sulfuric acid, sodium sulfide, sulfuryl chloride, hydrogen bromide, bromine, or iodine. The Te-C bond can also be broken thermally or through photostimulation. 

Related Reagents. Tributyltin hydride tris(trimethylsilyl) silane. 

The stereospecific base-cleavage of the trimethylsilyl group in 1,3-dithiane 1-oxides 499 enables to obtain the specifically deuteriated products 500 (equation 303), A nitro group in y-nitroalkyl sulphoxides 501 (obtained by the Michael addition of nitroalkanes to a, j8-unsaturated sulphoxides) is replaced by hydrogen by means of tributyltin hydride (equation 304). This reagent does not affect the sulphinyl function. The overall procedure provides an efficient method for the conjugate addition of alkyl groups to a, -unsaturated sulphoxides . ... 

In the presence of AIBN, tributyltin hydride is an excellent dehalogenating reagent for generating radicals. The bromoalkylcyclobutanone 206 undergoes reductive ring expansion to give, via the annealed alkoxy radical, the cis-fiised bicycle 207 stereospecifically as the major product [113], (Scheme 81)... 

The most commonly used method for synthesizing organotin hydrides with a hydrogen isotope bonded to the tin atom is to reduce the appropriate chlorostannanes with labelled hydride reagents, such as lithium aluminium deuteride or sodium borodeuteride. For example, tributylchlorostannane can be reduced with lithium aluminium deuteride42-45 or deuterated or tritiated sodium borohydride46 to give tributyltin deuteride and tritiated tributyltin hydride, respectively (equations 40 and 41). 

Hexabutyldistannane, which is an important reagent in many organic syntheses, can be prepared very conveniently by reducing bis(tributyltin) oxide with sodium borohydride in ethanol at room temperature. After 5 min, the only tin species present is tributyltin hydride, but in 2 h, its decomposition is catalyzed by the ethoxide ion that is formed to give the distannane in 83% yield.444 Hexaalkyldistannanes, R3SnSnR3 (R = Et, Pr, or Bu), are obtained in ca. 50% yield when the corresponding trialkyltin halides are treated with zinc powder in THF.445... 

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. 

Analogous transformations have been initiated using alternative methods. Tributyltin hydride and sodium naphthalenide [101], for example, were examined in an effort to probe the possible intermediacy of a radical or carbanion, respectively. The results were compared with those achieved electrochemically. As illustrated, the results were different for each set of reagents, though the sodium naphthalenide and electrochemical results are most similar. This information has b n used to suggest that a carbanion is formed electrochemically and participates in the cyclization event. 

Tributyltin hydride, 97%, was purchased from Aldrich Chemical Company, Inc. and used directly. A minimal excess of this reagent is desired in order to ensure clean distillation of 4. If the product is to be purified by chromatography, a 10% excess of tributyltin hydride can be used. 

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. 

The stereospecific preparation of E- and Z-a-fluorovinylstannanes via the radical reaction of the corresponding a-fluorovinylsulfones with tributyltin hydride has been reported by McCarthy et al. These reagents undergo a variety of destannylation reactions including protolysis, deuterolysis, acylation, iodina-tion, electrophilic fluorination and the Stille coupling reaction [186-189] (Scheme 66). The last reaction has been employed successfully in the synthesis of a fluorinated thymidylate synthetase inhibitor [189] (Scheme 67). 

Lithium butyldimethylzincate, 221 Lithium sec-butyldimethylzincate, 221 Organolithium reagents, 94 Organotitanium reagents, 213 Palladium(II) chloride, 234 Titanium(III) chloride-Diisobutylalu-minum hydride, 303 Tributyltin chloride, 315 Tributyl(trimethylsilyl)tin, 212 3-Trimethylsilyl-l, 2-butadiene, 305 Zinc-copper couple, 348 Intramolecular conjugate additions Alkylaluminum halides, 5 Potassium t-butoxide, 252 Tetrabutylammonium fluoride, 11 Titanium(IV) chloride, 304 Zirconium(IV) propoxide, 352 Miscellaneous reactions 2-(Phenylseleno)acrylonitrile, 244 9-(Phenylseleno)-9-borabicyclo[3.3.1]-nonane, 245 Quina alkaloids, 264 Tributyltin hydride, 316 Conjugate reduction (see Reduction reactions)... 

Norephedrine, 200 Organoaluminum reagents, 202 Organotitanium reagents, 213 9-(Phenylseleno)-9-borabicyclo-[3.3.1]nonane, 245 Tin(II) chloride, 298 Titanium(IV) chloride, 304 Trityllithium, 338 Trityl perchlorate, 339 Zinc chloride, 349 By other reactions Chloromethyl ethyl ether, 75 Dibutyltin oxide, 95 Samarium(II) iodide, 270 Tributyltin hydride, 316 Hydroxy amides a-Hydroxy amides... 

The simple addition reaction in Scheme 19 illustrates how the notation is used. Ester (1) can be dissected into synthons (2), (3) and (4). Synthons for radical precursors (pro-radicals) possess radical sites ( ) A reagent that is an appropriate radical precursor for the cyclohexyl radical, such as cyclohexyl iodide, is the actual equivalent of synthon (2). By nature, alkene acceptors have one site that reacts with a radical ( ) and one adjacent radical site ( ) that is created upon addition of a radical. Ethyl acrylate is a reagent that is equivalent to synthon (3). Atom or group donors are represented as sites that react with radicals ( ) Tributyltin hydride is a reagent equivalent of (4). In practice, such analysis will usually focus on carbon-carbon bond forming reactions and the atom transfer step may be omitted in the notation for simplicity. 

Catalytic procedures (introduced by Kuivila and Menapace92) are easier to conduct and the tin hydride concentration is more easily controlled. A catalytic amount of tributyltin hydride or tributyltin chloride is mixed with the radical precursor, the alkene acceptor and a stoichiometric quantity of a coreductant such as sodium borohydride93 or sodium cyanoborohydride.29 Over the course of the reaction, the borohydride continuously converts the tin halide to tin hydride. The use of the catalytic procedure is probably restricted to halide precursors (tin products derived from other precursors may not be reduced to tin hydrides). This method has several advantages over the standard procedures (i) it is simple to conduct (ii) most functional groups are stable to the coreductants (especially sodium cyanoborohydride) (iii) the tin hydride concentration is known, is stationary (assuming that the tin halide is rapidly reduced to tin hydride), and can be varied by either changing the concentration of the reaction or the quantity of the tin reagent (10% is a typical value, but lower quantities can be used) and finally, (iv) the amount of tin hydride precursor that is added limits the amount of tin by-product that must be removed at the end of the reaction. 

A radical eyclization was conducted with 2,2 -a/obisisobutyronitnle AIBN (37) as the radical initiator. Tributyltin hydride serves as the chain transfer reagent. Radical 38 arises from halide 15 through abstraction of an iodine atom, and this in turn cyclizes to radical 39. Compound 39 then abstracts a proton from tributyltin hydride. The resulting tributyltin hydnde radical reinitiates the radical mecha msm, in that it abstracts an iodine atom from another halide molecule 15 (see Chapter 14). 

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