Water-Compatible Iminium Activation: Organocatalytic Michael Reactions of Carbon-Centered Nucleophiles with Enals
作者:Claudio Palomo、Aitor Landa、Antonia Mielgo、Mikel Oiarbide、Ángel Puente、Silvia Vera
DOI:10.1002/anie.200703261
日期:2007.11.12
Highly Stereoselective Asymmetric Construction of an Acyclic Carbon Skeleton Having Two Adjacent Alkyl Substituents by Michael Addition of Optically Active Allenyltitaniums to Alkylidenemalonates
作者:Yongcheng Song、Sentaro Okamoto、Fumie Sato
DOI:10.1021/ol016652p
日期:2001.11.1
[GRAPHICS]Enantio-enriched allenyltitaniums prepared in situ by the reaction of optically active secondary propargyl phosphates with a divalent titanium reagent Ti(O-i-Pr)(4)/2i-PrMgCl react readily with alkylidenemalonates with excellent regio- and diastereoselectivities to afford the Michael addition products with a high optical purity, thus opening up a new asymmetric method for construction of an acyclic carbon skeleton bearing two adjacent alkyl substituents.
Stereoselective synthesis of alicyclic ketones: A hydrogen borrowing approach
作者:Roly J. Armstrong、Wasim M. Akhtar、James R. Frost、Kirsten E. Christensen、Neil G. Stevenson、Timothy J. Donohoe
DOI:10.1016/j.tet.2019.130680
日期:2019.11
A highly diastereoselective annulation strategy for the synthesis of alicyclic ketones from diols and pentamethylacetophenone is described. This process is mediated by a commercially available iridium(III) catalyst, and provides efficient access to a wide range of cyclopentane and cyclohexane products with high levels of stereoselectivity. The origins of diastereoselectivity in the annulation reaction
The conjugate addition of Ti “ate” complexes of ketone and ester enolates to α,β-unsaturated carbonyl compounds was studied. The reaction was found to be highly regio- and stereoselective. Compared to the lithium enolates, ketone enolate Ti complexes showed an improved 1,4-regioselectivity. t-Butyl propionate enolate Ti complex gave the opposite stereochemical results compared to the parent lithium