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Luche reduction is the selective 
The selectivity can be explained in terms of the 
In one application, a ketone is selectively reduced in the presence of an aldehyde. Actually, in the presence of methanol as solvent, the aldehyde forms a methoxy
organic reduction
Organic reductions or organic oxidations or organic redox reactions are redox reactions that take place with organic compounds. In organic chemistry oxidations and reductions are different from ordinary redox reactions, because many reactions car ...
of α,β-unsaturated ketones to allylic alcohols. The active reductant is described as "cerium borohydride", which is generated in situ from NaBH4 and CeCl3(H2O)7.
The Luche reduction can be conducted chemoselectively toward ketone
In organic chemistry, a ketone is an organic compound with the structure , where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group (a carbon-oxygen double bond C=O). The simplest ketone is acetone ( ...
in the presence of aldehyde
In organic chemistry, an aldehyde () (lat. ''al''cohol ''dehyd''rogenatum, dehydrogenated alcohol) is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred ...
s or towards α,β-unsaturated ketones in the presence of a non- conjugated ketone.
An enone forms an allylic alcohol
Allyl alcohol (IUPAC name: prop-2-en-1-ol) is an organic compound with the structural formula . Like many Alcohol (chemistry), alcohols, it is a water-soluble, colourless liquid. It is more toxic than typical small alcohols. Allyl alcohol is us ...
in a 1,2-addition, and the competing conjugate 1,4-addition is suppressed.
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The selectivity can be explained in terms of the HSAB theory
HSAB is an acronym for "hard and soft (Lewis) acids and bases". HSAB is widely used in chemistry for explaining the stability of compounds, reaction mechanisms and pathways. It assigns the terms 'hard' or 'soft', and 'acid' or 'base' to chemical ...
: carbonyl groups require hard nucleophiles for 1,2-addition. The hardness of the borohydride is increased by replacing hydride groups with alkoxide groups, a reaction catalyzed by the cerium salt by increasing the electrophilicity of the carbonyl group. This is selective for ketones because they are more Lewis basic.
:
In one application, a ketone is selectively reduced in the presence of an aldehyde. Actually, in the presence of methanol as solvent, the aldehyde forms a methoxy acetal
In organic chemistry, an acetal is a functional group with the connectivity . Here, the R groups can be organic fragments (a carbon atom, with arbitrary other atoms attached to that) or hydrogen, while the R' groups must be organic fragments n ...
that is inactive in the reducing conditions.
References
{{Reflist Organic reduction reactions Organic redox reactions Name reactions