Enantioselective <i>N</i>-Heterocyclic Carbene Catalysis via Acyl Azolium without Exogenous Oxidants
作者:Jing Cao、Rachel Gillard、Azar Jahanbakhsh、Martin Breugst、David W. Lupton
DOI:10.1021/acscatal.0c02705
日期:2020.10.16
An approach to the α,β-unsaturatedacylazolium has been developed that exploits N-heterocyclic carbenes (NHCs) and acyl fluorides, without additional oxidants, bases, or preactivated pro-nucleophiles. These conditions have been applied in four classes of NHC-catalyzed reaction. In all cases, the expected products were produced with high yield and enantioselectivity, using two sets of closely related
Combining<i>in situ</i>Generated Chiral Silicon Lewis Acid and Chiral Brønsted Acid Catalysts for [3+2] Cycloadditions: Cooperative Catalysis as a Convenient Enantioselective Route to Pyrazolidines
作者:Olga V. Serdyuk、Alexandru Zamfir、Frank Hampel、Svetlana B. Tsogoeva
DOI:10.1002/adsc.201200293
日期:2012.11.12
A facile enantioselective synthesis of chiral pyrazolidines via a [3+2] cycloadditionreaction, involving a BINOL-derived phosphoric acid and an in situ generated BINOL phosphate-derived siliconLewisacid, which may act cooperatively, has been developed.
Silicon Lewis Acid Catalyzed [3+2] Cycloaddition Reactions of Hydrazones/Cyclopentadiene: Mild Access to Pyrazolidine Derivatives
作者:Alexandru Zamfir、Sebastian Schenker、Walter Bauer、Timothy Clark、Svetlana B. Tsogoeva
DOI:10.1002/ejoc.201100206
日期:2011.7
A first and fairly mild metal-free catalytic route was developed for the [3+2] cycloadditions of different N-acylhydrazones to cyclopentadiene, providing the synthetically andbiologically important five-membered cyclic compounds pyrazolidines. The reaction was successfully conducted in high yields (up to 99 %) with high diastereoselectivities (up to 98:2 dr) by using catalytic amounts of TMSOTf (trimethylsilyl