Sodium triethylborohydride

Chemical routes involving the use of tungsten salts have been reported. W2C was claimed to be formed by the pyrolysis of an organometallic complex containing cyclopentadiene and carbonyl groups.8 The W2C formed was useful for ceramic applications such as wear resistant surfaces and cutting tools. The same phase was also prepared by the reduction of WC14 with sodium triethylborohydride.9 The material was formed as 1-5 nm-sized crystallites as shown by SEM and TEM. 

The chlorine atom of 5-chlorodibenzoborole 41 has previously been displaced by a variety of nucleophiles including hydride ion from sodium triethylborohydride <1996CHEC-II(2)919>. However, the reaction of 41 with excess lithium hydride in THF goes a step further to give lithium dihydrodibenzoborole 20. It is postulated that the reaction occurs by addition of hydride ion to 41, loss of lithium chloride from lithium salt 45, and addition of hydride ion to unsubstituted dibenzoborole (Scheme 4) <2000JOM168>. 

Sodium triethylborohydride (29) reacts with isoquinoline to yield the boron-activated enamine (30) which undergoes attack by electrophiles to produce 4-substitued isoquinolines (31 Scheme 6) in a convenient one-pot synthesis. 

Sodium pyridylselenate, 368 Sodium selenophenolate, 368-369 Sodium succinimide, 78 Sodium sulfide, 377 Sodium thioethoxide, 368 Sodium triethylborohydride-Iron(H) chloride, 369... 

DESULFURATION Molybdenum carbonyl. Sodium triethylborohydride-Iron(II) chloride. Tri-n-Butyltin hydride. 

Modification of the reaction conditions, such as higher temperatures, using different nonpolar aprotic solvents or addition of lithium bromide, iron(III) chloride, hydroquinone, or benzoyl peroxide slightly reduced the yield of the brominated cyclopropane. The bromine at the methyl group can be replaced by hydrogen in high yield using sodium triethylborohydride in... 

The difficulties encountered are, however, overcome by the use of disiamyl borane and sodium triethylborohydride [3] as the base, in a nonaqueous system. However, 9-BBN is an ideal for this purpose, and a wide variety of cyclopropane derivatives (Chart 16.1) [4-6] are prepared in good yields. 

Henkel-Loctite appears to have been careful to avoid the patent minefield laid by 3M and Dow. Their patent strategy in this field has involved mainly the use of metal alkali borohydrides [113,114], or tetralkylboranes [115-117]. In particular, alkali metal trialkyl borohydrides are used, the alkali metal salt being selected from lithinm triethylborohydride, sodium triethylborohydride, potassium triethylborohydride, lithium tri-sec-butylborohydride, sodium tri-sec-butylborohydride, potassium tri-sec-butylborohydride, and lithium triethylborodeuteride. 

H-l,3-ditellurole. Under an atmosphere of argon, 0.23 g (2.4 mmol) of trimethylsily-lacetylene are dissolved in 5 mL dry tetrahydrofuran. The solution is cooled to -70°C. n-Butyl lithium (1.0 mL, 2.4 M, 24 mmol) is dropped into the stirred solution. Then 0.20 g (2.0 mmol) of tellurium powder is added. The mixture is warmed to 20°C and kept at this temperature for 2 h. To this mixture, cooled again to -70°C, is added a solution of 0.35 g (2.0 mmol) of chloroiodomethane in 1 mL of tetrahydrofuran. The mixture is stirred for 15 min and then quenched with 50 mL water. The product is extracted with three 15 mL portions of dichloromethane. The combined extracts are washed with brine, dried with anhydrous sodium sulphate and filtered. The filtrate is concentrated to give trimethylsilylethynyl chloromethyl tellurium as a pale-yellow oil. Tellurium powder (0.125 g, 1.0 mmol) is added to 2 mL of a 1 M solution (2.0 mmol) of lithium triethylborohydride in ethanol. The mixture is stirred at 20°C for 2 h under an atmosphere of argon. Then 2 mL of 1 M sodinm ethoxide in ethanol are added followed by 0.27 g (1.0 mmol) of trimethylsilylethynyl chloromethyl tellurium dissolved in 2 mL dimethylformamide. The mixture is stirred for 15 h at 20°C, then diluted with 25 mL water and extracted with three 15 mL portions of dichloromethane. The combined extracts are dried with anhydrons sodinm snlphate, fdtered and the filtrate concentrated. The residue is chromatographed on silica gel with hexane/dichloromethane (1 1) as mobile phase. The fractions containing the prodnct are concentrated and recrystallized from methanol 65% yield, m.p. 85°C. 

Diphenyl telluropyran-4-one (typicalprocedure)7° 120 mL (0.12 mol) of a 1.0 M solution of lithium triethylborohydride in tetrahydrofuran are added to 7.65 g (60 mmol) of powdered tellurium under nitrogen, and the mixture stirred at 20°C for 4 h. A solution of sodium ethoxide (prepared from 5.52 g (0.24 mol) of sodium and 240 mL of absolute alcohol) is added to the dilithium telluride, 13.8 g (60 mmol) of bis(phenylethynyl) ketone are dissolved in a mixture of 150 mL of tetrahydrofuran and 150 mL of 1 M sodium ethoxide in ethanol this solution is poured as quickly as possible into the deep-purple-coloured dilithium telluride soluhon. The flask containing the reaction mixture is immediately placed in a water bath at 50°C and the temperature slowly increased over 30 min until ethanol begins to condense on the side of the flask. The water bath is removed and the mixture is stirred overnight at 20°C. Dichloromethane (400 mL) is then added, the resultant mixture is washed with 800 mL of water, and the organic phase is separated and concentrated to an oil. The oil is dissolved in 600 mL of dichloromethane, and the solution is filtered through a pad of sand. The filtrate is washed with 200 mL of 2% aqueous sodium chloride soluhon, dried with anhydrous sodium sulphate, filtered and evaporated. The brownish solid residue is triturated with 20 mL of butanenitrile and the fine yellow solid is collected by filtration yield 10.9 g (51%) m.p. 126-129°C (from acetonitrile). 

Replacement of hydrogen by alkyl groups gives compounds like lithium triethylborohydride (Super-Hydride ) [100], lithium tris sec-butyl)borohydride [101] (L-Selectride ) and potassium tris sec-butyl)borohydride (K-Selectride ) [702], Replacement by a cyano group yields sodium cyanoborohydride [103], a compound stable even at low pH (down to 3), and tetrabutylammonium cyanoborohydride [93],... 

Alkyl bromides and especially alkyl iodides are reduced faster than chlorides. Catalytic hydrogenation was accomplished in good yields using Raney nickel in the presence of potassium hydroxide [63] Procedure 5, p. 205). More frequently, bromides and iodides are reduced by hydrides [505] and complex hydrides in good to excellent yields [501, 504]. Most powerful are lithium triethylborohydride and lithium aluminum hydride [506]. Sodium borohydride reacts much more slowly. Since the complex hydrides are believed to react by an S 2 mechanism [505, 511], it is not surprising that secondary bromides and iodides react more slowly than the primary ones [506]. The reagent prepared from trimethoxylithium aluminum deuteride and cuprous iodide... 

Disulfides can be either reduced to two thiols or desulfurized. The former reaction was achieved in high yields using lithium aluminium hydride [680, 681], lithium triethylborohydride [100] and sodium borohydride [682]. 

Other reagents used for reduction are boranes and complex borohydrides. Lithium borohydride whose reducing power lies between that of lithium aluminum hydride and that of sodium borohydride reacts with esters sluggishly and requires refluxing for several hours in ether or tetrahydrofuran (in which it is more soluble) [750]. The reduction of esters with lithium borohydride is strongly catalyzed by boranes such as B-methoxy-9-bora-bicyclo[3.3.1]nonane and some other complex lithium borohydrides such as lithium triethylborohydride and lithium 9-borabicyclo[3.3.1]nonane. Addition of 10mol% of such hydrides shortens the time necessary for complete reduction of esters in ether or tetrahydrofuran from 8 hours to 0.5-1 hour [1060],... 

Potassium triethylborohydride, 260 Sodium borohydride, 21 Ring-forming reactions 2,2 -Dihydroxy-1,1 -binaphthyl, 113 Other asymmetric reactions Camphor-10-sulfonic acid, 62 Di-jjL-chlorobis(l,5-cyclooctadiene)di-rhodium-2,3-0-Isopropylidene-2,3-dihydroxy-1,4-bis(diphenyl-phosphine)butane, 153... 

Desulfonylation Lithium-Ammonia, 158 Lithium triethylborohydride, 168 Magnesium-Methanol, 170 Sodium dithionite, 281 Sodium naphthalenide, 294 Desulfurization Lithium aluminum hydride-Bis(cyclopentadienyl)nickel, 158 Lithium l-(dimethylamino)naph-thalenide, 165 Lithium-Ethylamine, 158 Dethioacetalization (see Hydrolysis of thioacetals and -ketals)... 

Potassium triethylborohydride, 260 Samarium(II) iodide, 270 Sodium-Alcohol, 277 Sodium borohydride, 21, 167 Sodium cyanoborohydride-Tin(II) chloride, 280... 

Tributyltin hydride, 316 Zinc iodide, 280 From alkyl halides Lithium aluminum hydride-Ceri-um(III) chloride, 159 Palladium catalysts, 230 Sodium cyanoborohydride-Tin(II) chloride, 280 From alkyl sulfonates Lithium triethylborohydride, 153 From thiols... 

Numerous reducing agents were tried at this point unsuccessfully. For example, lithium aluminum hydride destroyed the substrate, whereas DIBAH or lithium borohydnde in THF and sodium borohydride in ethanol led to reduction of the quinoline system. On the other hand, both potassium borohydride (either with or without 18-crown-6) and zinc borohydride (with or without ethanol) produced no reaction at all. Lithium triethylborohydride resulted in de-methoxylation, and sodium borohydride in refluxing THF gave a 45% yield of diol 16 together with overreduced product. 

An oven-dried 300-ml flask, equipped with a side-arm fitted with a silicone rubber septum, a magnetic stirrer bar, and a reflux condenser connected to a mercury bubbler, is cooled to room temperature under a stream of dry nitrogen. Tetrahydrofuran (20 ml) is introduced, followed by 7.1 g (25 mmol) of cyclooctyl tosylate (1). The mixture is cooled to 0 °C (ice bath). To this stirred solution, lithium triethylborohydride (Section 4.2.49, p. 448) [33.3 ml (50 mmol) of a 1.5 m solution in tetrahydrofuran] is added, and the ice bath removed. The mixture is stirred for 2 hours (c. 25 °C). Excess hydride is decomposed with water. The organoborane is oxidised with 20 ml of 3 m sodium hydroxide solution and 20 ml of 30 per cent hydrogen peroxide [(2) and (3)]. Then the tetrahydrofuran layer is separated. The aqueous layer is extracted with 2 x 20 ml portions of pentane. The combined organic extracts are washed with 4 x 15 ml portions of water to remove ethanol produced in the oxidation. The organic extract is dried (MgS04) and volatile solvents removed by distillation (2). Distillation of the residue yields 2.27 g (81%) of cyclooctane as a colourless liquid, b.p. 142-146 °C, Wq0 1.4630. 

Hydrazine, lithium triethylborohydride, and sodium benzenethiolate produced the tellurium halides only in low yields3. 

Lithium telluride, prepared from tellurium and lithium triethylborohydride in tetrahydrofuran2, and sodium telluride, obtained from sodium and tellurium in a dipolar, aprotic solvent or from tellurium2,5 and Rongalite in aqueous sodium hydroxide2, reacted with aliphatic2,3,6 and aromatic5 dihalides to produce polymeric organo tellurium compounds. 

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