Lithium triethylborohydride chlorides

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). 

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... 

Using boron-based reagents Chlorodiisopinocampheylborane, 72 Lithium triethylborohydride, 205 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... 

Dienes Ferric chloride, 133 Lithium triethylborohydride, 168 Zinc, 346... 

To complete the synthesis of the nucleotide hosts, the hindered tweezer esters needed to be converted to the corresponding carboxylic acids. One possible method presented itself with the surprising finding that treatment of 45 with lithium triethylborohydride produced the corresponding carboxylic acid However, lithium triethylborohydride did not react at all with the more hindered ester in 27. Neither could the esters in molecular tweezers 27-30 and 48 be converted to the corresponding carboxylic acids (31-34, 49) hydrolytically. Therefore, the nucleophilic reagents, boron trichloride in methylene chloride or cyanide in hot DMSO, were employed with success [56]. 

Hydrolysis to Nonproteinogenic Amino Acids. Numerous amino acids, including a-branched ones, have been prepared from Boc-BMI. Only a few examples can be alluded to here (11) from (5)-(l), EtI, and Br(CH2)4Cl (12) from (5)-(l), 3-methylbutanoyl chloride, and Lithium Triethylborohydride (13) from (R)-(l), butanal, and dibutylcuprate (14) from (S)-(l) and 4-phenylbut-2-enoate. ... 

For reasons of brevity we report only the principal four syntheses. Dibenzocyclooctene 67 was hydrogenated affording a mixture of two cis lactones (68) and (69) (the second one probably arises due to the isomerization of the double bond), Scheme (13). Reduction of the lactones lead to a single diol 70. Treatment with methanesufonyl chloride in pyridine followed by lithium triethylborohydride reduction completed the synthesis of (-)-wuweisizu C (71) [65],... 

Attempts to convert the sulfones back into PASHs have been successful with a number of agents such as various metals (zinc, tin, magnesium, aluminum, iron, and nickel) in acetic acid, palladium on carbon with hydrazine, stannous chloride, lithium triethylborohydride, diphenylsi-lane, sodium borohydride, boron trifluoride, dicyclohexylcarbodiimide, triethyl phosphite, dimethyl dichlorosUane with lithium aluminum hydride, diphenylsilane, and triphenyl phosphine with iodine. However, none of them cleanly effect this conversion. 

Hindered t-alkyl halides with lithium triethylborohydride in the presence of chromous chloride furnish highly crowded coupled products in good yield (equation 111) . Alkanes obtained by hydroalumination of alkenes with LAH in the presence of titanium tetrachloride can be dimerized in the presence of cupric acetate to furnish alkanes (equation 112) ... 

Lithium hydride, prepared in an activated form according to equation (3), has been shown to reduce esters, aldehydes, and ketones to alcohols in the presence of equimolar vanadium (ill) chloride." Lithium hydride can also be used to prepare lithium triethylborohydride [equation (4)], and full details of... 

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>. 

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... 

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