Hydride, tri-n-butyltin

In a fume hood, 19.2 g. (0.059 mole) of tri-n-butyltin chloride and then 140 ml. of ethylene glycol dimethyl ether (monoglyme) which has been purified by distillation from calcium hydride at atmospheric pressure on an efficient fractionating column (fraction used boils at 85 1°C.) are added to a pressure-equalized 250-ml. dropping funnel, and the funnel gently agitated to dissolve all the tributyltin chloride. 

After the flask containing the sodium borohydride solution has cooled for about half an hour, the tributyltin chloride solution is added dropwise with rapid stirring over a 30-minute period. A white sodium chloride precipitate forms as each drop of the tributyltin chloride solution is added. The reaction mixture is allowed to stand at —10 to — 11°C. for 10-15 minutes after the last of the tributyltin chloride solution has been added. Without filtration, the entire reaction mixture is now transferred cold under nitrogen or helium into a 1-1., single-necked, round-bottomed flask the flask is attached to a flash evaporator (Buchler Model PTFE-1G or equivalent) and immersed in a bath maintained at 0°C. The evaporator s receiving flask (also 1-1., single-necked, round-bottomed) is immersed in a — 80°C. bath of Dry Ice-acetone. 

The evaporation flask is now removed from the flash evaporator, and the residue (which may appear to be dry) is extracted under nitrogen or helium with three 25-ml. portions of anhydrous, peroxide-free diethyl ether. The ether extract is poured through a medium sintered-glass frit under an atmosphere of nitrogen or helium. Finally, the ether is removed by pumping on the filtered extract at 0°C. for 30-40 minutes. A pressure of less than 1 mm. is maintained. The colorless liquid product is identified as tri-n-butyltin hydride from its liquid-phase infrared spectrum11 and refractive index, n 1.4715, literature, 1.4711 (extrapolated from f 1.472612 and 1.47206). The yield is 16.5 g. (0.057 mole, 96%). 

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Cyclopentene derivatives with carboxylic acid side-chains can be stereoselectively hydroxy-lated by the iodolactonization procedure (E.J. Corey, 1969, 1970). To the trisubstituted cyclopentene described on p. 210 a large iodine cation is added stereoselectively to the less hindered -side of the 9,10 double bond. Lactone formation occurs on the intermediate iod-onium ion specifically at C-9ot. Later the iodine is reductively removed with tri-n-butyltin hydride. The cyclopentane ring now bears all oxygen and carbon substituents in the right stereochemistry, and the carbon chains can be built starting from the C-8 and C-12 substit""" ... 

Bowmer and Tonelli [161] have also studied the thermal characteristics of the whole range of ethylene-vinyl chloride copolymers prepared by partial reductive dechlorination of PVC using tri-n-butyltin-hydride. Naqvi [162] has substantiated further his explanations for the thermal stability characteristics of ethylene-vinyl chloride copolymers reported by Braun et al. [159] using the results of Bowmer and Tonelli [161] as a basis. 

In an effort to identify a more stereoselective route to dihydroagarofuran (15), trimethylsilylated alkyne 17 was utilized as a substrate for radical cyclization (Scheme 2). Treatment of 17 with a catalytic amount of AIBN and tri-n-butyltin hydride (1.25 equiv) furnishes a mixture of stereoisomeric vinyl silanes 18 (72% combined yield) along with an uncyclized reduction product (13% yield). The production of stereoisomeric vinyl silanes in this cyclization is inconsequential because both are converted to the same alkene 19 upon protodesiiyiation. Finally, a diastereoselective di-imide reduction of the double bond in 19 furnishes dihydroagaro-... 

If the reaction just described is conducted in the presence of a suitable hydrogen atom donor such as tri-n-butyltin hydride or tert-butyl hydrosulfide, reductive decarboxylation occurs via a radical chain mechanism to give an alkane (see 125—>128, Scheme 24). Carboxylic acids can thus be decarboxylated through the intermediacy of their corresponding thiohydroxamate esters in two easily executed steps. In this reducjtive process, one carbon atom, the carbonyl carbon, is smoothly excised... 

Remarkable solvent effects on the selective bond cleavage are observed in the reductive elimination of cis-stilbene episulfone by complex metal hydrides. When diethyl ether or [bis(2-methoxyethyl)]ether is used as the solvent, dibenzyl sulfone is formed along with cis-stilbene. However, no dibenzyl sulfone is produced when cis-stilbene episulfone is treated with lithium aluminum hydride in tetrahydrofuran at room temperature (equation 42). Elimination of phenylsulfonyl group by tri-n-butyltin hydride proceeds by a radical chain mechanism (equations 43 and 44). 

Tri-n-butyltin hydride can also be used for reductive demercuration.20 An alternative reagent for demercuration is sodium amalgam in a protic solvent. Here the evidence is that free radicals are not involved and the mercury is replaced with retention of configuration.21... 

Other reactive forms of nickel including nickel boride283 and nickel alkoxide complexes284 can also be used for desulfurization. Tri-n-butyltin hydride is an alternative reagent for desulfurization.285... 

Starnes and Bovey (1) pioneered the method of I3C NMR analysis of reduced poly(vinyl chloride) (PVC) to study the microstructure of PVC. Tri-n-butyltin hydride ((n-Bu)3SnH) was found to completely dechlorinate PVC resulting in polyethylene (PE) whose microstructure (branching, end-groups, etc.) could be sensitively studied by 13C NMR. 

One of the first fully characterized (monofluoromethyl)silicon compounds, CH2FSiEt3, had been obtained previously by reduction of CHFBrSiEt3 with tri-n-butyltin hydride, CHFBrSiEt3 being synthesized by insertion of CFBr into the SiH bond of triethylsilane [8]. 

Feldman and Eastman have suggested that the kinamycins may by reductively activated to form reactive vinyl radical (25) and orf/to-quinone methide (26) intermediates (Scheme 3.2c) [16]. The authors provided convincing evidence that the alkenyl radical 25 is generated when the model substrate dimethyl prekinamycin (24) is exposed to reducing conditions (tri-n-butyltin hydride, AIBN). Products that may arise from addition of this radical (25) to aromatic solvents (benzene, anisole, and benzonitrile) were isolated. The ort/io-quinone methide 26 was also formed,... 

Recently, Kondo and coworkers reported on the polymerization of St with diphenyl diselenides (37) as the photoiniferters (Eq. 39) [ 162]. In the photopolymerization of St in the presence of 37a and 37b, the polymer yield and the molecular weight of the polymers increased with reaction time. The chain-end structure of the resulting polymer 38 was characterized. Polymer 38 underwent the reductive elimination of terminal seleno groups by reaction with tri-n-butyltin hydride in the presence of AIBN (Eq. 40). It also afforded the poly(St) with double bonds at both chain ends when it was treated with hydrogen peroxide (Eq. 41). They also reported the polymerization of St with diphenyl ditelluride to afford well-controlled molecular weight and its distribution [163]. 

The asymmetric induction in the formation of (231) proceeds via a bromonium ion 231c). Denomination of (231a) with tri-n-butyltin hydride followed by saponification gave the chiral a-hydroxycarboxylic acid (232) in high optical purity. (S)-proline was recovered for recycling. 

Reduction of propargylic chlorides with tri-n-butyltin hydride to a mixture of the corresponding acetylene and isomeric allene [92],... 

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