P. Ramachandran, A. Teodorović, M. V. Rangaishenvi
Apr 1, 1992
Citations
0
Influential Citations
56
Citations
Journal
Journal of Organic Chemistry
Abstract
The Midland reagent, Alpine-Borane (2a), is excellent for the asymmetric reduction of many acetylenic ketones, but it fails with hindered derivatives. On the other hand, B-chlorodiisopinocampheylborane (DIP-Chloride, 4) reacts with hindered α,β-acetylenic ketones to provide the corresponding propargylic alcohols in 96 to ≥99% ee. The reaction is in accordance with the tentative mechanism proposed earlier. While 4-phenyl-3-butyn-2-one is reduced in only 21% ee, 4 reduces 4-methyl-1-phenyl-1-pentyn-3-one in 53% ee and 4,4-dimethyl-1-phenyl-1-pentyn-3-one in ≥99% ee