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Luche reduction of enones using cerium trichloride; allylic alcohols

SyntheticPage 22
DOI: 10.1039/SP22
Submitted Jul 02, 2001, published Jul 03, 2001
zac etheridge (
A contribution from Caddick, Sussex

			Reaction Scheme: <IMG src="/images/empty.gif">Luche reduction of enones using cerium trichloride<IMG src="/images/empty.gif">

Chemicals Used

4-Acetoxy-5-tbutyldimethylsilyloxy-cyclopent-2-en-1-one (245 mg, 0.91 mmol)
Sodium borohydride (powdered, 50 mg, 1.42 mmol)
Cerium trichloride heptahydrate (dried in vacuum, 450 mg, 1.22 mmol)
Methanol (distilled from CaH2, 4mL)


This procedure is used for the chemoselective reduction of enones to produce allylic alcohols, in this case (and many others) with a good degree of stereospecificity. The enone and cerium trichloride are stirred in methanol at 0C and the sodium borohydride is added portionwise over about 15 minutes; some effervescence should be seen. Stirring is continued at this temperature until completion (TLC), usually about 1.5-2 hours, then quenched with ammonium chloride solution, extracted 4 times with ethyl acetate, washed with brine, dreid over magnesium sulphate, filtered, concentrated and purified by column chromatography eluting with 20% EtOAc/PE

Author's Comments

The yield is 80% of the desired trans, trans isomer in this case, with 8% of the undesired cis, trans isomer also being isolated. No reduction of the alkene is observed. The reaction is slightly moisture sensitive and thus fresh, powdered sodium borohydride should be used, and the cerium trichloride should be dried for a few hours under vacuum first. The reaction has also been carried out in the presence of a free hydroxy group in a slightly reduced yield (60-70%).


1HNMR (300MHz, CDCl3) 5.83 (1H, d), 5.72 (1H, d), 5.23 (1H, s), 4.39 (1H, s), 4.04 (1H, t), 1.98 (3H, s), 0.81 (9H, s), 0.03 (3H, s), 0.00 (3H, s).

Lead Reference

Luche JL, Rodriguez-Hahn L, Crabbe P. J. Chem. Soc. Chem. Comm. 1978 p.601

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Keywords: enone, luche reduction, sodium borohydride, cerium trichloride, allylic alcohol, reduction, heterocyclic compounds

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