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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:
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]
Some alcohols are reduced to alkanes when treated with hydrosilanes in the presence of a strong Lewis acid. Brønsted acids may also be used. Tertiary alcohols undergo facile reduction using boron trifluoride etherate as the Lewis acid. [2] Primary alcohols require an excess of the silane, a stronger Lewis acid, and long reaction times. [3]
Enantioselective ketone reductions convert prochiral ketones into chiral, non-racemic alcohols and are used heavily for the synthesis of stereodefined alcohols. [1]Carbonyl reduction, the net addition of H 2 across a carbon-oxygen double bond, is an important way to prepare alcohols.
Importantly, the reaction effectively reduced the two ketones, alcohol, and the methoxycarbonyl group while avoiding any by-products, giving the product in high yield (61%). Scheme 3: The synthesis of Dibarrelane. [12] Clemmensen reduction is not particularly effective with aliphatic or cyclic ketones.
The Wharton olefin synthesis or the Wharton reaction is a chemical reaction that involves the reduction of α,β-epoxy ketones using hydrazine to give allylic alcohols. [1] [2] [3] This reaction, introduced in 1961 by P. S. Wharton, is an extension of the Wolff–Kishner reduction.
The aluminium based Meerwein–Ponndorf–Verley reduction can be performed on prochiral ketones leading to chiral alcohols. The three main ways to achieve the asymmetric reduction is by use of a chiral alcohol hydride source, use of an intramolecular MPV reduction, or use of a chiral ligand on the aluminium alkoxide.
Using an alcohol instead of water yields an ether (see also Hofmann-Sand reaction). In both cases, Markovnikov's rule is observed. Other applications of oxymercuration. Using a vinyl ether in the presence of an alcohol allows the replacement of one alkoxy group (RO–) for another by way of an acetal intermediate.