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Lithium aluminium hydride, commonly abbreviated to LAH, is an inorganic compound with the chemical formula Li[Al H 4] ... Similarly, it converts amide, [24] [25] ...
Some amides can be reduced to aldehydes in the Sonn-Müller method, but most routes to aldehydes involve a well-chosen organometallic reductant. Lithium aluminum hydride reduces an excess of N,N-disubstituted amides to an aldehyde: [citation needed] R(CO)NRR' + LiAlH 4 → RCHO + HNRR' With further reduction the alcohol is obtained.
Lithium amide or lithium azanide is an inorganic compound with the chemical formula LiNH 2. It is a white solid with a tetragonal crystal structure. [1] Lithium amide can be made by treating lithium metal with liquid ammonia: [2] 2 Li + 2 NH 3 → 2 LiNH 2 + H 2. Lithium amide decomposes into ammonia and lithium imide upon heating. [3]
The lithium amides are more common and more soluble than the other alkali metal analogs. Potassium amides are prepared by transmetallation of lithium amides with potassium t-butoxide (see also Schlosser base) or by reaction of the amine with potassium, potassium hydride, n-butylpotassium, or benzylpotassium. [2]
The final step in the reduction of carboxylic acids and esters is hydrolysis of the aluminium alcoxide. [8] Esters (and amides) are more easily reduced than the parent carboxylic acids. Their reduction affords alcohols and amines, respectively. [9] The idealized equation for the reduction of an ester by lithium aluminium hydride is:
Nahm and Weinreb also reported the synthesis of aldehydes by reduction of the amide with an excess of lithium aluminum hydride (see amide reduction). The Weinreb–Nahm ketone synthesis. The major advantage of this method over addition of organometallic reagents to more typical acyl compounds is that it avoids the common problem of over-addition.
The tertiary amide was stable to the reaction conditions and reduced subsequently by lithium aluminum hydride. [38] Scheme 18. Synthsesis of Aspidospermidine. Amides are usually not suitable substrates for the Wolff–Kishner reduction as demonstrated by the example above.
As a hydride reducing agent, lithium borohydride is stronger than sodium borohydride [6] [7] but weaker than lithium aluminium hydride. [7] Unlike the sodium analog, it can reduce esters to alcohols, nitriles and primary amides to amines, and can open epoxides.