Non-chelation controlled 1,3-asymmetric induction in β-chiral acylsilanes
摘要:
The diastereoselectivity of nucleophilic adition to beta-chiral acylsilanes is examined, and our method is applied to the stereoselective synthesis of calcitriol lactone, a major metabolite of vitamine D-3.
improved generation of chiral cationic iridium catalysts for the asymmetricisomerization of primaryallylicalcohols is disclosed. The design of these air‐stable complexes relied on the preliminary mechanistic information available, and on Charton analyses using two preceding generations of iridium catalysts developed for this highly challenging transformation. Sterically unbiased chiral aldehydes
We report herein the enantioselectiveCu-catalyzed conjugate addition of organometallic reagents to sensitive Michael acceptors and their application to the synthesis of relevant target molecules. This is one of the most important methodologies to form a C-C bond in an enantioselective manner. A wide range of alpha,beta-unsaturated aldehydes and beta,gamma-unsaturated-alpha-ketoesters has been successfully
The first asymmetric Cu-catalyzed conjugate addition of dialkylzinc zinc reagents to a large scope of enals in presence of phosphoramidite, SimplePhos, or (R)-BINAP ligands with enantiomeric excesses up to 90% is reported. Moreover, ACA of Grignard reagents afforded moderate to good 1,4-regioselectivities with enantioselectivities up to 90%.
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
Iminium Catalysis inside a Self-Assembled Supramolecular Capsule: Modulation of Enantiomeric Excess
作者:Thomas M. Bräuer、Qi Zhang、Konrad Tiefenbacher
DOI:10.1002/anie.201602382
日期:2016.6.27
The noncovalent combination of a supramolecular host with iminiumorganocatalysis is described. Due to cation–π interactions the reactiveiminium species is held inside the host and reacts in this confined environment. The products formed differ up to 92 % ee from the control experiments without added host. A model rationalizing the observed difference is presented.