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Reduction of Carbonyl Compounds by Lanthanide Metal/2‐Propanol: In‐situ Generation of Samarium Isopropyloxide for Stereoselective Meerwein−Ponndorf−Verley Reduction
Author(s) -
Fukuzawa Shinichi,
Nakano Narihito,
Saitoh Takahide
Publication year - 2004
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200400030
Subject(s) - chemistry , samarium , acetophenone , stereoselectivity , lanthanide , transfer hydrogenation , pinacol , hydride , catalysis , yield (engineering) , metal , medicinal chemistry , methanol , ligand (biochemistry) , alcohol , organic chemistry , ruthenium , ion , materials science , metallurgy , biochemistry , receptor
The reduction of ketones and aldehydes with lanthanide metals (La, Ce, Sm, Yb) and a catalytic amount of iodine (5 mol %) in i PrOH 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/ i PrOH were higher than those achieved with SmI 2 / i PrOH or Sm/H 2 O. 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)