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Lithium borohydride (LiBH 4) is a borohydride and known in organic synthesis as a reducing agent for esters.Although less common than the related sodium borohydride, the lithium salt offers some advantages, being a stronger reducing agent and highly soluble in ethers, whilst remaining safer to handle than lithium aluminium hydride.
An example of an ester formation is the substitution reaction between a carboxylic acid (R−C(=O)−OH) and an alcohol (R'OH), forming an ester (R−C(=O)−O−R'), where R and R′ are organyl groups, or H in the case of esters of formic acid.
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:
It has also been shown to reduce aromatic esters to the corresponding alcohols as shown in eq 6 and 7. LiBHEt 3 also reduces pyridine and isoquinolines to piperidines and tetrahydroisoquinolines respectively. [7] The reduction of β-hydroxysulfinyl imines with catecholborane and LiBHEt 3 produces anti-1,3-amino alcohols shown in (8). [8]
The selectivity of this reagent is illustrated by its reduction of all three methylcyclohexanones to the less stable methylcyclohexanols in >98% yield. Under certain conditions, L-selectride can selectively reduce enones by conjugate addition of hydride, owing to the greater steric hindrance the bulky hydride reagent experiences at the carbonyl ...
The Bouveault–Blanc reduction is a chemical reaction in which an ester is reduced to primary alcohols using absolute ethanol and sodium metal. [1] It was first reported by Louis Bouveault and Gustave Louis Blanc in 1903. [2] [3] [4] Bouveault and Blanc demonstrated the reduction of ethyl oleate and n-butyl oleate to oleyl alcohol. [5]
The reaction is performed in aprotic solvents with a high boiling point, such as benzene and toluene, in an oxygen-free atmosphere (as even traces of oxygen interfere with the reaction path and reduce the yield). Protic solvents effect the Bouveault-Blanc ester reduction rather than condensation.
Luche reduction is the selective organic reduction of α,β-unsaturated ketones to allylic alcohols. [ 1 ] [ 2 ] [ 3 ] The active reductant is described as "cerium borohydride", which is generated in situ from NaBH 4 and CeCl 3 (H 2 O) 7 .