Introduction <P>Lithium hydroxide is a mild and efficient reagent used in several transformations
in organic synthesis. It is used in tandem intramolecular aldol-aldol and sequential
intramolecular Michael-aldol
[
1 ]
reactions, as promoter of fragmentation reactions of optically active carbolactones
providing γ-hydroxycyclohexenones and γ-butenolides,
[
2 ]
in the synthesis of tropolones useful as bidentate ligands,
[
3 ]
as promoter of glucosilation of 1-hydroxyindoles,
[
4 ]
in the stereoselective Michael addition of thiols to
N -methacryloylcamphorsultam followed by hydrolysis of the sulfonamides,
[
5 ]
and it is applied in the deacylation of diazo-oxazolidones.
[
6 ]
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In addition, lithium hydroxide has been widely employed in Horner-Wadsworth-Emmons
(HWE) reactions for preparation of α,β-unsaturated esters, α-unsaturated esters
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8 ]
[
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and α,β-unsaturated nitriles.
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10 ]
</P><P>Abstracts</P>
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(A) Mischne reported a synthesis of [4.4.0] or [5.3.0] bicyclic frameworks achieved
via sequential intramolecular Michael-aldol and tandem intramolecular aldol-aldol
strategies, starting from acyclic precursors derived from β-ionone.
[1
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(B) Khim et al. reported that lithium hydroxide induced fragmentation in butenolides
and γ-hydroxycyclohexenones. The addition of LiOH (2.0 equiv) to a solution of the
carbolactone in THF-H2 O (5:1) at room temperature resulted in a mixture of the butenolides and γ-hydroxycyclohexenones
in excellent yield.
[2
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(C) Lemal and co-workers showed that anhydrous lithium hydroxide in benzene transforms
tropone into pentafluorotropolone, which functions as a bidentate ligand (72% yield).
[3
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(D) Yamada et al. reported a lithium hydroxide promoted glucosidation of 1-hydroxyindoles
with 2,3,4,6-tetra-O -acetyl-α-d -glucopyranosyl bromide followed by acetylation with Ac2 O and pyridine.
[4
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(E) Tsai et al. showed that lithium base (LiOH) promotes stereoselective Michael
addition of thiols to N -methacryloylcamphorsultam and produced the corresponding addition products with
a diastereomeric ratio of 66-90%. Hydrolysis of the Michael product with three equivalents
of lithium hydroxide in THF-H2 O gave the corresponding optically active β-thioester without racemization, and camphorsultam
was recovered quantitatively.
[5
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(F) Lithium hydroxide promotes selective deacylation of diazo-oxazolidones resulting
in N -diazoacetyl derivatives.
[6 7
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(G) Lattanzi et al. showed a mild and practical procedure of LiOH-promoted HWE olefination,
in which aldehydes were reacted with α-cyano phosphonates, yielding α,β-unsaturated
nitriles. The reaction conditions are tolerated by functionalized ketones and the
exclusive formation of (E )-γ-hydroxy α,β-unsaturated nitriles was observed.
[10
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(H) Karagiozov and Abbott reported a stereoselective synthesis of α,β-unsaturated
esters achieved via HWE reaction of β,β-disubstituted α,β-unsaturated aldehydes.
Thus, aldehydes undergo olefination with phosphonate carbanion generated from triethyl
phosphonoacetate and lithium hydroxide to give (E )-α,β-unsaturated esters in excellent selectivity.
[9
