Simple Chiral Diene Ligands Provide High Enantioselectivities in Transition-Metal-Catalyzed Conjugate Addition Reactions
作者:Kazuhiro Okamoto、Tamio Hayashi、Viresh H. Rawal
DOI:10.1021/ol801931v
日期:2008.10.2
Chiral dienes possessing the bicyclo[2.2.2]octadiene framework were prepared readily through the [4 + 2] cycloaddition of ( R)-alpha-phellandrene with methyl propiolate as the key step. Diene 9, substituted with a tertiary alcohol on one of the two double bonds, is prepared in just one step from the cycloadduct and is highly effective as a chiralligand for rhodium-catalyzedasymmetricconjugate addition
Stereoselective Construction of 1,3-Disilylcyclopentane Derivatives by Scandium-Catalyzed [3+2] Cycloaddition of Allylsilanes to β-Silylenones
作者:Kazuhiro Okamoto、Eisuke Tamura、Kouichi Ohe
DOI:10.1002/anie.201404218
日期:2014.9.15
The Sc(OTf)3‐catalyzed [3+2] cycloaddition of allylsilanes to β‐silyl‐α,β‐unsaturated ketones (β‐silylenones) has been developed to form five‐membered syn‐1,3‐disilylketones diastereoselectively through the rearrangement of the silicon substituents on the allylsilane. Stabilization of the carbocation intermediates by a double silicon effect plays a key role in directing the course of the reaction to
Solvent-free synthesis of enantioenriched β-silyl nitroalkanes under organocatalytic conditions
作者:Akhil K Dubey、Raghunath Chowdhury
DOI:10.3762/bjoc.17.177
日期:——
carbonyl compounds catalyzed by bifunctional squaramide catalysts has been developed. This methodology offers both enantiomers of β-silyl nitroalkanes in good to excellent yields (up to 92%) and enantioselectivities (up to 97.5% ee) under solvent-free conditions at room temperature. Control experiments reveal that the presence of a β-silyl group in the enones is crucial for high reactivityunder the optimized