Monodentate N-Ligand-Directed Bifunctional Transition-Metal Catalysis: Highly Enantioselective Friedel-Crafts Alkylation of Indoles with Nitroalkenes
作者:Fengfeng Guo、Guoyin Lai、Shunshun Xiong、Sujing Wang、Zhiyong Wang
DOI:10.1002/chem.201000540
日期:2010.6.11
A role beyond base: A highly efficient, asymmetric Friedel–Craftsalkylation of indoles with nitroalkenes is presented that uses simple nitrogen compounds combined with Schiff base zinc(II) complexes as bifunctional catalysts (see scheme). The nitrogen compounds here play a crucial role as ligands as well as their traditional role as bases.
Rhodium-Catalyzed Asymmetric Addition of Arylboronic Acids to Indolylnitroalkenes
作者:Junwei Xing、Guihua Chen、Peng Cao、Jian Liao
DOI:10.1002/ejoc.201101648
日期:2012.2
bioactive structures. Most approaches to access chiral indolylnitroethanes involve organocatalyzed or metal-catalyzed asymmetric FriedelCrafts reaction of indoles with nitroalkenes. We have developed an efficient approach to optically pure a-aryl-3-indolylnitroethanes through rhodium-catalyzed asymmetric 1,4-addition of arylboronicacids to indolylnitroalkenes. Excellent yields (up to 99?%) and enantiomeric
Leveraging the anion binding properties of thioureas, we show that the activity of known well-performing chiral catalysts can be reduced by coordinating anions (e.g. chloride) and restored by anion metatheses. Three benchmark enantioselective transformations were successfully studied, demonstrating the reversibility of the activation/deactivation processes.