Sodium borohydride alkyl halides

It has been shown that phenylselenyl halides easily reacted with 0-allyl oximes 221 to give cyclic iminium salts 222, which by reaction with water afforded isoxazolidines 223 in moderate to good yields (equation 96) . Compounds 222 can be reduced in situ by sodium borohydride to produce Ai-alkyl-substituted isoxazolidines 224 in 50-95% yields . ... 

In general, alkylations as well as some acylations of enamines using halides as the leaving group occur predominantly on carbon (B-69MI20700). For example, treatment of A2-piperideine (115) with methyl bromoacetate followed by sodium borohydride reduction... 

Reduction of RCOCI to RCHO. Sodium borohydride and this cadmium salt reduce acyl chlorides to aldehydes, but only in solvents such as DMF, DMA, and HMPT. DMF is essential, but the amount of DMF in the salt is sufficient. For the most part, yields are 50-90%. Aryl, alkyl, and benzylic halides do not react. Other functional groups (nitrile, nitro, ester, C=C) are also inert. 

The first step consists of the formation of lithio salts by treatment of 5,6-dihydrooxazines with phenyl-, n-butyl-, or t-butyllithium in tetra-hydrofuran at -780.1,3,22,223 The lithio salts can readily be alkylated by alkyl halides to 75, and the product can be reduced with aqueous sodium borohydride (or borodeuteride) at pH 7 in tetrahydrofuran-ethanol-water at -35° to -45°C to tetrahydro-l,3-oxazines (76) in quantitative yield. The latter 224-228 23e on hydrolysis with aqueous oxalic acid give aldehydes (77) [Eq. (63)]. 

Superhydride has also been used for the hydrogenolysis of alkyl toluene-p-sulphonates, and an illustrative example is given in Expt 5.4 for the preparation of cyclooctane from cyclooctyl toluene-p-sulphonate. A sodium borohydride hydrogenolysis of alkyl halides and of alkyl methane- and toluene-p-sulphonates under PTC conditions provides an interesting variant of this reaction.9... 

A one-pot PTC reaction procedure for the overall conversion of an alkyl halide into a primary amine via an azide is particularly illustrative.204 Thus the reduction of the azide is effected by the addition of sodium borohydride to a reaction mixture arising from the PTC displacement reaction of an alkyl halide with sodium azide (the preparation of 1-octylamine, Expt 5.193). The reaction appears to be applicable to primary and secondary alkyl halides, alkyl methane-sulphonates and benzylic halides. 

Alkyl mercury halides and alkyl mercury acetates are quite stable, but reduction with sodium borohydride leads to highly unstable alkyl mercury hydrides, which collapse at room temperature or in the presence of light to yield alkyl radicals. One other product is mercury metal and you might think you would get H as well but this is too unstable to be formed and is captured by something else (X)—you will see what X is in a moment. This initial decomposition of RHgH initiates the chain but its propagation is by the different mechanism shown below. 

Sodium borohydride, a representative borohydride reagent, behaves as an effective source of nucleophilic hydride in an aprotic polar solvent, such as DMSO, sulfolane, HMPA, DMF or diglyme, and is used for the reduction of alkyl halides. As shown in Table 3, primary and secondary iodides, bromides and chlorides are converted to hydrocarbons at temperatures between 25 and 100 C using sodium borohydride. Vicinal dihalides, such as 1,2-dibromooctane, are smoothly converted to the corresponding saturated hydrocarbons, in contrast to the reductions using LiAlH4 or low-valent metal salts, which predominantly afford alkenes. 

Some alkyl halides (primary I, Br, Cl and secondary Br) are reduced by NaBH4 under phase-transfer conditions, as shown in equation (4). This reaction is carried out by the addition of a concentrated aqueous solution of NaBH4 to a stirred solution of substrate and catalyst in a suitable solvent, such as toluene. Yields are nearly quantitative in most cases, although an excess of sodium borohydride is required. 

Sodium 1-methylethanetellurolate and hexadecanetellurolate were obtained from sodium hydrogen telluride and the appropriate alkyl halide in THF or THF/ethanol. The sodium hydrogen telluride was prepared from tellurium and sodium borohydride in water. Equimolar amounts of disodium telluride combined with aliphatic carboxylic acid chlorides in tetrahydrofuran at — 30" and with aromatic carboxylic acid chlorides in tetrahydrofuran at 0° to give sodium tellurolates that have an acyl group bonded to the tellurium atom. These tellurolates, the sodium salts of tellurolocarboxylic acids, are dark-red substances that were obtained in almost quantitative yields. 

The reaction of disodium telluride with alkyl halides is the oldest known method for the preparation of dialkyl telluriums. The required solutions of disodium telluride can be prepared from tellurium and sodium formaldehyde sulfoxylate (Rongalite C) in aqueous sodium hydroxide (Vol. IX, p. 1048), from tellurium and sodium in liquid ammonia " dimethylformamide or tetrahydrofuran in the presence of naphthalene , from tellurium and hydrazine hydrate/sodium hydroxide in water or dimethylformamide °, from tellurium and thiourea dioxide in aqueous tetrahydrofuranor from tellurium and sodium borohydride in methanol, ethanol, tetrahydrofuran, or aqueous sodium hydroxide ... 

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