Long Zhang

Magnetic nanoparticle supported ionic liquid catalysts for CO2cycloaddition reactions

MNP-supported ionic liquid catalysts (MNP-ILs) were developed and evaluated in CO2cycloaddition reactions under a lower CO2 pressure (1 MPa), showing essentially unchanged activity after 11 reuses.

Asymmetric SN1 α‐Alkylation of Cyclic Ketones Catalyzed by Functionalized Chiral Ionic Liquid (FCIL) Organocatalysts

Echoed with the sustainable chemistry concept, the developments of highly efficient and practical asymmetric catalysts have been and continue to be the fore of organic synthesis. Functionalized chiral ionic liquids (FCILs), which combine the green credential of ionic liquids and the catalytic principles of modern asymmetric catalysis, have recently appeared as such a type of asymmetric catalyst. Following the initial work of Howarth and Seddon; the applications of FCILs have moved beyond the use as chiral additives, chiral reagents, or chiral inducing reaction media, and now have reached the stage of asymmetric catalysts. However, the promising potentials of FCILs as asymmetric catalysts still remain largely underdeveloped at present and the current successes have been primarily confined to the reactions like Michael additions and aldol reactions. As such, in our continuing efforts in exploring this type of catal ACHTUNGTRENNUNGysis,[5d–f, n] we have sought new reaction development by taking advantage of the intrinsic properties of ionic liquids. Herein, we report the first FCIL-catalyzed enantioselective SN1 type alkylation of cyclic ketones, in which the ionic liquid moieties are found to be critical for both the catalytic activity and stereocontrol. The catalytic asymmetric direct a-alkylation reaction of carbonyl compounds has long been a daunting challenge in asymmetric catalysis and synthesis. Before the renaissance of organocatalysis, particularly the enamine-based amino ACHTUNGTRENNUNGcatACHTUNGTRENNUNGalysis, asymmetric phase-transfer catalysis was the only successful approach to this end and it was mostly used in the synthesis of a-amino acids through alkylation of glycine derivatives. In 2004, Vignola and List reported the first catalytic intramolecular nucleophilic a-alkylation of aldehydes by means of enamine activation. Later on, several cascade reactions including an intramolecular a-alkylation of aldehydes as the key step were also reported. However, the intermolecular a-alkylation of aldehydes or ketones are still a challenging task due to the depletion of catalytic activity through the N-alkylation of the aminocatalysts and various competing bypaths therewith. The past few years have witnessed notable breakthroughs in the development of asymmetric intermolecular a-alkylations of carbonyl compounds, specifically of aldehydes. Melchiorre and Cozzi have independently reported SN1 type aalkylation of aldehydes by enamine catalysis. This novel approach was based on alkyl donors endowed with suitable leaving groups (Scheme 1, I), which can generate a stabi-

Chiral Amine Thiourea-Promoted Enantioselective Michael Addition Reactions of 3-Substituted Benzofuran-2(3H)-ones to Maleimides

A highly diastereo- and enantioselective Michael addition reaction with respect to prochiral 3-substituted benzofuran-2(3H)-ones and maleimides by a chiral bifunctional thiourea-tertiary amine catalyst was investigated. The corresponding adducts, containing a quaternary center at the C3-position of the benzofuran-2(3H)-one as well as a vicinal tertiary center, were generally obtained in high yields (up to 99%) with very good diastereo- (up to >20:1 dr) and enantioselectivities (up to 97% ee).

CCDC 787619: Experimental Crystal Structure Determination

Related Article: Xin Li, Shenshen Hu, Zhiguo Xi, Long Zhang, Sanzhong Luo, Jin-Pei Cheng|2010|J.Org.Chem.|75|8697|doi:10.1021/jo101832e