Chiral thiourea compounds and process for enantioselective reduction of ketones
申请人:Li Derun
公开号:US20090253919A1
公开(公告)日:2009-10-08
Chiral thioureas are effective catalysts for the borane reduction of prochiral ketones to optically active alcohols. A prochiral ketone may be reduced to an optically active alcohol in the presence of a substantially sub-stoichiometric amount of chiral thiourea. The asymmetric thiourea compound of the present invention may be produced according to a production method described herein.
Reactivity and regio- and enantioselectivities were strongly dependent on reaction conditions and substrates. Good to excellent regio- and enantioselectivities were obtained with zinc reagents R2Zn and aluminum reagents R3Al. However, the asymmetric conjugate addition of Grignard reagents afforded only moderate to good regio- and enantioselectivities. β-Substituted aldehydes constitute a very important
Skipping out: The title reaction using internal secondary allylic phosphates proceeded with excellent γ regioselectivity and E stereoselectivity to give skipped enynes. Enantioenriched secondary allylic phosphates proceeded with 1,3‐anti stereochemistry to afford the corresponding chiral 1,4‐enynes, which were used for various derivatizations and the formal total synthesis of a GnRH antagonist. phen=1
Rearrangement of Allylic and Propargylic Alcohols Catalyzed by the Combined Use of tetrabutylammonium perrhenate (VII) and p-toluenesulfonic acid
作者:Koichi Narasaka、Hiroyuki Kusama、Yujiro Hayashi
DOI:10.1016/s0040-4020(01)88874-8
日期:1992.1
Allylic rearrangement and/or dehydration reaction of allylic alcohols proceeds smoothly by the use of catalytic amounts of tetrabutylammonium perrhenate and p-toluenesulfonic acid hydrate. Treatment of propargylic alcohols with the catalysts at room temperature affords the rearranged products, α,β-unsaturated carbonyl compounds, while, β,γ-unsaturated ketones are obtained as main products by the reaction
that selectively iodinates electron-rich aromatics. In contrast to other common electrophilic iodinating reagents, its mild nature allows it to be used for the selective synthesis of α-iodinated carbonyl compounds fromallylicalcohols through a 1,3-hydrogen shift / iodination process catalyzed by iridium(III) complexes.