Catalytic enantioselective Steglich rearrangements using chiral N-heterocyclic carbenes
摘要:
The evaluation of a range of enantiomerically pure NHCs, prepared in situ from imidazolinium or triazolium salt precatalysts, to promote the catalytic enantioselective Steglich rearrangement of oxazolyl carbonates to their C-carboxyazlactones, is reported. Modest levels of enantioselectivity (up to 66% ee) are observed using oxazolidinone derived NHCs. (C) 2011 Elsevier Ltd. All rights reserved.
Enantioselective N‐Heterocyclic Carbene Catalysis by the Umpolung of α,β‐Unsaturated Ketones
作者:Yuji Nakano、David W. Lupton
DOI:10.1002/anie.201510106
日期:2016.2.24
N‐Heterocycliccarbene‐catalyzed formation of β‐anionic intermediates from enones has been employed in the enantioselective synthesis of 2‐aryl propionates. The reaction was achievable using a homochiral 4‐MeOC6H4 morpholinone catalyst allowing the first example of enantioselective catalysis by umpolung of α,β‐unsaturated ketones. The reaction is high yielding, and shows robustness with reasonable
N-杂环卡宾催化由烯酮形成的β-阴离子中间体已用于2-芳基丙酸酯的对映选择性合成。该反应可以通过使用手性4-MeOC 6 H 4吗啉酮催化剂来实现,这是通过α,β-不饱和酮的负载进行对映选择性催化的第一个例子。该反应收率高,并且具有合理的一般性的稳健性。提出了一种机制,其中使用六氟异丙醇或形成的萘酚产物实现对映体确定质子化。
Enantioconvergent Synthesis of Functionalized γ-Butyrolactones via (3 + 2)-Annulation
作者:C. Guy Goodman、Morgan M. Walker、Jeffrey S. Johnson
DOI:10.1021/ja511701j
日期:2015.1.14
A dynamic kineticresolution of β-halo α-keto esters in an asymmetric homoenolate reaction is described. A chiral N-hetereocyclic carbene catalyzes the a3 → d3-umpolung addition of α,β-enals to racemic α-keto esters, forming γ-butyrolactones with threecontiguousstereocenters. The addition occurs with high regio-, diastereo-, and enantiocontrol. This methodology constitutes an intermolecular DKR process