Lithium aluminum hydride LiAlH

Dimethoxyamphetamine. A solution of the above nitropropene (17.0 g) in 500 ml of dry ether is added slowly to a stirred solution of lithium aluminum hydride (LiAlH or LAH) 12 g suspended in 150 ml of dry ether. After completing the addition, the mixture is refluxed for 20 hours, then cooled. The excess LAH is decomposed by careful addition of water. The resulting suspension is filtered and the solid removed is washed with ether. The combined ether solutions are dried with MgS04, and then saturated with dry hydrogen chloride. This precipitates the title compound which is filtered and recrystallized from ethanol. Yield 13 g, mp 111.5-112.5°. 

The reduction of carboxylic acids or esters requires very powerful reducing agents such as lithium aluminum hydride (LiAlH,) or sodium (Na) metal. Aldehydes and ketones are easier to reduce, so they can use sodium borohy-dride (NaBH,j). Examples of these reductions are shown in Figure 3-13. 

The azide ion is a better nucleophile than amines, but it has to be reduced to the cimine cifter nucleophilic substitution. Lithium aluminum hydride (LiAlH ) in ether followed by treatment with water reduces the azide ion to the amine. Figures 13-11 and 13-12 illustrate two examples of this reaction. 

A number of organic species, including amides, oximes, and nitriles, undergo reductive amination, a variety of reduction reactions that produce cimines. In general, these processes involve imines, R=N-R, or related species. Reduction processes include hydrogenation using Raney nickel as the catalyst (for nitriles), the reaction with sodium/EtOH (for oximes), and the use of lithium aluminum hydride, LiAlH (for amides or nitriles). Figure 13-16 illustrates the preparation of amphetamine by reductive amination. 

Lithium aluminum hydride, LiAlH, in anhydrous ether can also be used. 

In these formulas, the R or R group may be either an aliphatic or aromatic group. In a ketone, the R and R groups may represent the same group or different groups. These types of compounds are best reduced by complex metal hydrides, such as lithium aluminum hydride (LiAlH) or sodium borohydride (NaBU). 

Lithium. Lithium aluminum hydride, LiAlH, is the only lithium compound of interest for Li analysis in IH work. Little work has been reported, except for standard ionization interferences (3) corrected by addition of 1000 ppm Cs to the final solution. 

Lithium aluminum hydride, LiAlH, is another reducing agent often used for reduction of ketones and aldehydes. A grayish powder soluble in ether and tetrahydrofuran, LiAlH4 is much more reactive than NaBH4 but also more dangerous. It reacts violently with water and decomposes explosively when heated above 120°C. 

Reduction of a variety of compounds that contain the carbonyl group provides s)mthetic methods to produce primary and secondary alcohols. A common, very powerful reducing agent is lithium aluminum hydride, LiAlH other reducing agents include sodium in alcohol and sodium borohydride, NaBH. ... 

Lithium aluminum hydride LiAlH. a reducing agent in many organic syntheses. 

Sodium borohydride (NaBH ) can reduce aldehydes and ketones when reacted in aqueous or alcohol solutions. Carboxylic acids and esters are not reactive to sodium borohydride reduction. Lithium aluminum hydride (LiAlH ), a more powerful reducing agent, can reduce aldehydes, ketones, esters, and carboxylic acids. 

On the other hand, the number of highly reactive chemicals that advance from the sta of laboratory curiosities to commercial items is constantly increasing, Some of these are sodium hydride (NaH), lithium aluminum hydride (LiAlH ), lithium borohydride (LiBH ), aluminum and beryllium borohydride, Al(BH4)3 and BefBH ), the sodium salt of nitromethane sodium methane nitronate or if one prefers sodium nitro methanate (HjCNOgNa), - and barium carbide (BaCg)/ all of which can flame on contact with water. Again, it must be stressed that particle size and other conditions of exposure may determine whether there is flaming or merely a violent reaction on exposure to water, air, or both. 

Lithium aluminum hydride, LiAlH (LAH), reduces a carboxylic acid to a primary alcohol in excellent yield, although heating is required. LAH is usually dissolved in diethyl ether or tetrahydrofuran (THF). When carboiylic acids react with LiAlH,, the initial product is a tetraalkoxy aluminate ion, which is then treated with water to give the primary alcohol and lithium and aluminum hydroxides. These hydroxides are insoluble in diethyl ether and THF and are removed by filtration. Evaporation of the solvent then yields the primary alcohol. 

Scheme 9.113. A representation of the reduction of the cyclohexene derivative (cis-l-methyl-3-oxa-2,4-dioxobicyclo[4.3.0]-7-nonene, cis-l-methyl-cyclohex-4-ene-l,3-dicarboxyUc acid anhydride) with lithium aluminum hydride (LiAlH,) to produce the corresponding lactone, cM-l-methyl-3-oxa-4-oxobicyclo[4.3.0]-7-nonene (cw-l-methyl-l-hydroxymethylcyclohex-4-...

In addition to the usual substitution reactions directly on the nitrogen atom of the amino or amido group, there are (as noted earlier, e.g.. Table 7.7) substitution reactions with other nucleophiles that can be converted to the amino (or substituted amino) group. These include incorporation of the azido function (produced by, e.g., a nucleophilic substitution reaction of azide anion [Ns"] on an alkyl halide) and its subsequent reduction (with lithium aluminum hydride, LiALH,) (Equation 10.60) or triphenylphosphine [( 5115)3 ] (Equation 10.61) to the corresponding amine, as well as a similar displacement reaction with isocyanate (0=C=N ) (Equation... 

Dirnethoxy-4-hydroxyphenylethylamine Hydrochloride (4 ) Phenylethylamine 4a can be prepared using a general procedure for the reduction of, S-nitrostyrenes to the corresponding phenylethylamines using lithium aluminum hydride (LiAlH.,). To 0.938 g (25 mmoles) of LiAlH., in 100 ml of dry tetrahydrofuran = is added dropwise a solution of 3,5-dimethoxy-4-benzyloxy-,8-nitrostyrene 3a, 1.5 g, 4.76 mmoles) dissolved in 100 ml of dry tetrahydrofuran. The addition takes approximately 1 hr, after which the reaction mixture is refluxed for 3 hr and then cooled in an ice bath. Excess LiAlHi is decomposed by dropwise addition of other that is saturated with water, followed by dropwise addition of... 

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