Reduction of Carbonyl Compounds by Lanthanide Metal/2-Propanol: In-situ Generation of Samarium Isopropyloxide for Stereoselective Meerwein−Ponndorf−Verley Reduction

The reduction of ketones and aldehydes with lanthanide metals (La, Ce, Sm, Yb) and a catalytic amount of iodine (5 mol %) in iPrOH proceeded smoothly to produce the corresponding alcohols as the major products in good yield, while in THF, methanol, and ethanol the pinacols were mainly produced. The...

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Bibliographic Details
Published in:European journal of organic chemistry 2004-07, Vol.2004 (13), p.2863-2867
Main Authors: Fukuzawa, Shin-ichi, Nakano, Narihito, Saitoh, Takahide
Format: Article
Language:English
Subjects:
Lanthanides
Meerwein−Ponndorf−Verley reduction
Reductions
Samarium
Samarium alkoxide
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Summary:The reduction of ketones and aldehydes with lanthanide metals (La, Ce, Sm, Yb) and a catalytic amount of iodine (5 mol %) in iPrOH proceeded smoothly to produce the corresponding alcohols as the major products in good yield, while in THF, methanol, and ethanol the pinacols were mainly produced. The yields of alcohols were improved most effectively by the use of Sm metal, the amount of pinacol produced thus being minimized. The actual reducing agent may be samarium isopropyloxide, which mediates the Meerwein−Ponndorf−Verley‐type hydride‐transfer reaction, since the reaction can be carried out catalytically with respect to samarium. The stereoselectivities of the reductions of the 2‐ and 4‐substituted cyclohexanones with Sm/iPrOH were higher than those achieved with SmI2/iPrOH or Sm/H2O. The asymmetric reduction of acetophenone could be achieved to give the 1‐phenylethanol in up to 95% ee in the presence of the chiral ligand 7. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
ISSN:1434-193X
1099-0690
DOI:10.1002/ejoc.200400030