796966-21-7Relevant articles and documents
Asymmetric Catalysis in Liquid Confinement: Probing the Performance of Novel Chiral Rhodium–Diene Complexes in Microemulsions and Conventional Solvents
Deimling, Max,Kirchhof, Manuel,Schwager, Barbara,Qawasmi, Yaseen,Savin, Alex,Mühlh?user, Tina,Frey, Wolfgang,Claasen, Birgit,Baro, Angelika,Sottmann, Thomas,Laschat, Sabine
, p. 9464 - 9476 (2019)
The role of liquid confinement on the asymmetric Rh catalysis was studied using the 1,2-addition of phenylboroxine (2) to N-tosylimine 1 in the presence of [RhCl(C2H4)2]2 and chiral diene ligands as benchmark reaction. To get access to Rh complexes of different polarity, enantiomerically pure C2-symmetric p-substituted 3,6-diphenylbicyclo[3.3.0]octadienes 4 and diastereomerically enriched unsymmetric norbornadienes 5 and 6 carrying either the Evans or the SuperQuat auxiliary were synthesized. A microemulsion containing the equal amounts of H2O/KOH and toluene/reactants was formulated using the hydrophilic sugar surfactant n-octyl β-d-glucopyranoside (C8G1) to mediate the miscibility between the nonpolar reactants and KOH, needed to activate the Rh–diene complex. Prominent features of this organized reaction medium are its temperature insensitivity as well as the presence of water and toluene-rich compartments with a domain size of 55 ? confirmed by small-angle X-ray scattering (SAXS). Although bicyclooctadiene ligands 4 a,b,e performed equally well under homogeneous and microemulsion conditions, ligands 4 c,d gave a different chemoselectivity. For norbornadienes 5, 6, however, microemulsions markedly improved conversion and enantioselectivity as well as reaction rate, as was confirmed by kinetic studies using ligand 5 b.
Efficient and Spatially Controlled Functionalization of SBA-15 and Initial Results in Asymmetric Rh-Catalyzed 1,2-Additions under Confinement
Beurer, Ann-Katrin,Kirchhof, Manuel,Bruckner, Johanna R.,Frey, Wolfgang,Baro, Angelika,Dyballa, Michael,Giesselmann, Frank,Laschat, Sabine,Traa, Yvonne
, p. 2407 - 2419 (2021/04/19)
Selectively functionalized mesoporous silica may considerably advance heterogeneous catalysis through the controlled immobilization of highly selective complex catalysts inside the mesopores. However, spatially controlled functionalization and the precise analytical verification are still a challenge. In this publication, we report a method, which ensures a selective functionalization of the mesopore surface with a clickable linker and thus makes it possible to study confinement effects during catalyzed reactions. First, we passivate the silanol groups on the particle surface and in the pore entrances of the mesoporous silica material SBA-15 with 1,1,1-trimethyl-N-(trimethylsilyl)silanamine. Then we remove the template by solvent extraction and functionalize the pore walls with 3-azidopropyltriethoxysilane before we click the catalyst. In initial experiments of asymmetric Rh-catalyzed 1,2-addition, we investigate the performance of a catalyst clicked selectively in the mesopores and compare it to the dissolved catalyst as well as to the catalyst immobilized exclusively on the external surface of SBA-15.
Experimental and Theoretical Study on the Role of Monomeric vs Dimeric Rhodium Oxazolidinone Norbornadiene Complexes in Catalytic Asymmetric 1,2- And 1,4-Additions
Abitaev, Karina,Alvarez-Barcia, Sonia,Baro, Angelika,Bauer, Alina,Bauer, Matthias,Estes, Deven P.,Fischer, Felix Richard,Frey, Wolfgang,Gugeler, Katrin,K?stner, Johannes,Kirchhof, Manuel,Laschat, Sabine,Nowakowski, Michal,Plietker, Bernd,Qawasmi, Yaseen,Ringenberg, Mark R.,Schnierle, Marc,Sottmann, Thomas
supporting information, p. 3131 - 3145 (2020/10/02)
The influence of nuclearity and charge of chiral Rh diene complexes on the activity and enantioselectivity in catalytic asymmetric 1,2-additions of organoboron reagents to N-tosylimines and 1,4-additions to enones was investigated. For this purpose, catio
