5329-93-1Relevant articles and documents
Electron-rich triarylphosphines as nucleophilic catalysts for oxa-Michael reactions
Boese, A. Daniel,Fischer, Susanne M.,Renner, Simon,Slugovc, Christian
supporting information, p. 1689 - 1697 (2021/08/03)
Electron-rich triarylphosphines, namely 4-(methoxyphenyl)diphenylphosphine (MMTPP) and tris(4-trimethoxyphenyl)phosphine (TMTPP), outperform commonly used triphenylphosphine (TPP) in catalyzing oxa-Michael additions. A matrix consisting of three differently strong Michael acceptors and four alcohols of varying acidity was used to assess the activity of the three catalysts. All test reactions were performed with 1 mol % catalyst loading, under solvent-free conditions and at room temperature. The results reveal a decisive superiority of TMTPP for converting poor and intermediate Michael acceptors such as acrylamide and acrylonitrile and for converting less acidic alcohols like isopropanol. With stronger Michael acceptors and more acidic alcohols, the impact of the more electron-rich catalysts is less pronounced. The experimental activity trend was rationalized by calculating the Michael acceptor affinities of all phosphine-Michael acceptor combinations. Besides this parameter, the acidity of the alcohol has a strong impact on the reaction speed. The oxidation stability of the phosphines was also evaluated and the most electron-rich TMTPP was found to be only slightly more sensitive to oxidation than TPP. Finally, the catalysts were employed in the oxa- Michael polymerization of 2-hydroxyethyl acrylate. With TMTPP polymers characterized by number average molar masses of about 1200 g/mol at room temperature are accessible. Polymerizations carried out at 80°C resulted in macromolecules containing a considerable share of Rauhut-Currier-type repeat units and consequently lower molar masses were obtained.
Template catalysis by manganese pincer complexes: Oxa- and aza-Michael additions to unsaturated nitriles
Tang, Shan,Milstein, David
, p. 8990 - 8994 (2019/10/22)
Activation of CN bonds by metal-ligand cooperation provides a new route for the functionalization of nitriles. Herein, we report the electrophilic activation of unsaturated nitriles by dearomatized manganese pincer complexes for the oxa- and aza-Michael addition reactions under very mild and neutral conditions. Derivatives of acrylonitrile and allyl cyanide furnished the corresponding β-addition products by reacting with alcohols and amines. Mechanistically, the catalysis is mostly ligand based. Reaction of the dearomatized PNN-Mn complex with 2-pentenenitrile or 3-pentenenitrile furnished an enamido-Mn complex. The equilibrium between an enamido complex and a ketimido complex, and reversible C-C bond formation with the ligand are proposed to play central roles in the catalysis.
Simple Copper Catalysts for the Aerobic Oxidation of Amines: Selectivity Control by the Counterion
Xu, Boran,Hartigan, Elizabeth M.,Feula, Giancarlo,Huang, Zheng,Lumb, Jean-Philip,Arndtsen, Bruce A.
supporting information, p. 15802 - 15806 (2016/12/16)
We describe the use of simple copper-salt catalysts in the selective aerobic oxidation of amines to nitriles or imines. These catalysts are marked by their exceptional efficiency, operate at ambient temperature and pressure, and allow the oxidation of amines without expensive ligands or additives. This study highlights the significant role counterions can play in controlling selectivity in catalytic aerobic oxidations.
