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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.
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]
Amide reduction is a reaction in organic synthesis where an amide is reduced to either an amine or an aldehyde functional group. [1] [2] Catalytic hydrogenation
In organic chemistry, carbonyl reduction is the conversion of any carbonyl group, usually to an alcohol. It is a common transformation that is practiced in many ways. [1] Ketones, aldehydes, carboxylic acids, esters, amides, and acid halides - some of the most pervasive functional groups, -comprise carbonyl compounds.
Reduction via the net transfer of hydrogen from one organic molecule to another is known as transfer hydrogenation. Transfer hydrogenation to ketones leads to alcohols (the Meerwein-Ponndorf-Verley reduction ), and in the presence of a chiral transition metal catalyst, this process may be rendered enantioselective.
Lithium hydride is an inorganic compound with the formula Li H.This alkali metal hydride is a colorless solid, although commercial samples are grey. Characteristic of a salt-like (ionic) hydride, it has a high melting point, and it is not soluble but reactive with all protic organic solvents.
Chiral auxiliaries are incorporated into synthetic routes to control the absolute configuration of stereogenic centers. David A. Evans' synthesis of the macrolide cytovaricin, considered a classic, utilizes oxazolidinone chiral auxiliaries for one asymmetric alkylation reaction and four asymmetric aldol reactions, setting the absolute stereochemistry of nine stereocenters.
Partial reduction of acid chlorides to give the corresponding aldehyde product cannot proceed via LAH, since the latter reduces all the way to the primary alcohol. Instead, the milder lithium tri- tert -butoxyaluminum hydride , which reacts significantly faster with the acid chloride than with the aldehyde, must be used.