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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 8, Number 4
April 20, 1987 

Asymmetric Reduction of Prochiral α,β-Acetylenic Ketones With Potassium 9-0-(1,2 : 5,6-Di-O-isopropylidene-α-D-glucofuranosyl)-9-bortabicylco[3.3.1]nonane
Byung Tae Cho*, Won Suh Park
The asymmetric reduction of representative prochiral α,β-acetylenic ketones with a new chiral borohydride reducing agent, potassium 9-0-(1,2: 5,6-Di-O-isopropylidene-α -D-glucofuranosyl)-9-boratabicyclo[3.3.1]nonane, 1, in THF at -78℃ was studied. Structurally different acetylenic ketones such as internal α ,β-acetylenic ketones RC ≡ CCOCH3 and terminal α,β-acetylenic ketones HC ≡ CCOR were chosen. Thus, the reduction of internal α,β-acetylenic ketones yields the corresponding propargyl alcohols, such as 67% ee for 3-hexyn-2-one, 75% ee for 5-methyl-3-hexyn-2-one, 86% ee for 5,5-dimethyl-3-hexyn-2-one, 74% ee for 3-nonyn-2-one and 61% ee for 4-phenyl-3-butyn-2-one. Terminal α,β-acetylenic ketones, such as 3-butyn-2-one, 1-pentyn-3-one, 4-methyl-1-pentyn-3-one and 1-octyn-3-one, are reduced to the corresponding alcohols with 59% ee, 17% ee, 44% ee and 12% ee of optical induction respectively. With one exception (4-methyl-1-pentyn-3-one), all propargyl alcohols obtained are enriched in R-enantiomers.
257 - 260
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