575451-08-0Relevant articles and documents
Cu-Catalyzed Diastereo- and Enantioselective Reactions of γ,γ-Disubstituted Allyldiboron Compounds with Ketones
Meek, Simon J.,Zanghi, Joseph M.
, p. 8451 - 8455 (2020/04/22)
A catalytic diastereo- and enantioselective method for the preparation of complex tertiary homoallylic alcohols containing a vicinal quaternary carbon stereogenic center and a versatile alkenylboronic ester is disclosed. Transformations are promoted by 5 mol % of a readily available copper catalyst bearing a bulky monodentate phosphoramidite ligand, which is essential for attaining both high dr and er. Reactions proceed with a wide variety of ketones and allylic 1,1-diboronate reagents, which enables the efficient preparation of diverse array of molecular scaffolds.
Enantioselective Synthesis of Functionalized Arenes by Nickel-Catalyzed Site-Selective Hydroarylation of 1,3-Dienes with Aryl Boronates
Marcum, Justin S.,Meek, Simon J.,Taylor, Tiffany R.
, p. 14070 - 14075 (2020/06/10)
A catalytic method for the site-selective and enantioselective synthesis of functionalized arenes by the intermolecular hydroarylation of terminal and internal 1,3-dienes with aryl pinacolato boronates is reported. The reactions are promoted by 5.0 mol %
Coordination studies on supramolecular chiral ligands and application in asymmetric hydroformylation
Bellini, Rosalba,Reek, Joost N. H.
, p. 7091 - 7099 (2012/07/27)
In this study we introduce a series of monodentate pyridine-based ligands for which the phosphorus coordination mode to rhodium can be controlled by the binding of ZnII-templates to the pyridyl group. A series of monodentate phosphoroamidite and phosphite ligands have been prepared and studied under hydroformylation conditions by in situ high-pressure NMR and IR techniques. These studies reveal the exclusive formation of rhodium hydride complexes in which the phosphorus atom of the ligand resides in an axial position, trans to the hydride, but only after addition of Zn II-template. In the absence of these templates the usual mono-coordinated rhodium hydrido complexes are formed, with the phosphorus ligated in the equatorial plane, cis to the hydride. The catalytic performance of these complexes is evaluated in asymmetric hydroformylation of unfunctionalised internal alkenes in which the supramolecular change is reflected in higher activity and selectivity.
Supramolecular hybrid bidentate ligands in asymmetric hydrogenation
Bellini, Rosalba,Reek, Joost N. H.
, p. 4684 - 4693 (2013/01/15)
In this study we introduce a novel class of supramolecular bidentate hybrid ligands and their application in the rhodium-catalysed asymmetric hydrogenation of prochiral olefins. A new supramolecular strategy is reported in which the two nonequivalent phosphorus atoms are linked covalently to a chiral scaffold, and the supramolecular interactions are used to control the second coordination sphere of the transition-metal catalyst. The supramolecular assembly is formed in situ by selective interaction between the nitrogen-donor atoms and the zinc(II) template, which is essential for obtaining high activity and selectivity. The investigations of the different zinc(II) and ruthenium(II) templates on the reaction parameters revealed a dependence of the activity and selectivity on the association constant between the supramolecular template and the pyridyl ligands. The scope of the supramolecular assemblies was explored in the Rh-catalysed asymmetric hydrogenation of α-dehydroamino acid esters and Roche ester derivatives. High activities and good to excellent enantioselectivities up to 99 % ee were obtained with the supramolecular ligands. Application of the supramolecular strategy on the basis of variations of the steric and electronic properties of zinc(II) templates demonstrate that these changes can influence key reaction parameters such as activity and selectivity. Copyright
Application of supramolecular bidentate hybrid ligands in asymmetric hydroformylation
Bellini, Rosalba,Reek, Joost N. H.
, p. 13510 - 13519,10 (2020/09/14)
In this study we report a novel class of supramolecular bidentate hybrid ligands in which the two inequivalent phosphorus units and pyridine moieties are covalently attached to a chiral scaffold and the supramolecular interactions are used as a second handle to control the coordination sphere around the transition-metal centre. The coordination chemistry of these ligands was investigated under hydroformylation conditions by high-pressure NMR and IR spectroscopy, revealing the formation of a single active species in which the phosphane ligand is in the axial position and the phosphoramidite adopts the equatorial position. These ligands were applied in the asymmetric Rh-catalysed hydroformylation of styrene and para-substituted analogues. In these hydroformylation reactions, modification of the electronic and steric properties of the zinc(II)-templates appear to have a significant influence on the activity and selectivity of the catalysis. In particular, zinc(II)-templates bearing more electron-withdrawing substituents led to an increase in enantioselectivity.
Supramolecular control of ligand coordination and implications in hydroformylation reactions
Bellini, Rosalba,Chikkali, Samir H.,Berthon-Gelloz, Guillaume,Reek, Joost N. H.
supporting information; scheme or table, p. 7342 - 7345 (2011/10/04)
The coordination mode of a monodentate phosphoroamidite ligand in a rhodium complex can be switched from equatorial to axial by a unique supramolecular pseudo encapsulation (see scheme). The axial complex has higher activity and selectivity in the challenging asymmetric hydroformylation of internal alkenes. Copyright
Synthesis and structural aspects of N-triflylphosphoramides and their calcium salts'highly acidic and effective Bronsted acids
Rueping, Magnus,Nachtsheim, Boris J.,Koenigs, Rene M.,Ieawsuwan, Winai
experimental part, p. 13116 - 13126 (2011/02/24)
Recently, 1,1′-bi-2-naphthol (BINOL)-based N-triflylphosphoramides emerged as a new class of potent Bronsted acid catalysts. In this paper we describe the efficient synthesis of various BINOL-based N- triflylphosphoramides and their calcium salts. Furthermore, X-ray crystal structure analysis combined with energy-dispersive X-ray spectroscopy (EDX) measurements confirmed that the synthesised chiral N-triflylphosphoramides are highly acidic metal-free catalysts. Freedom! The synthesis and structure determination of various 1,1′-bi-2-naphthol (BINOL)-based N-triflylphosphoramides and their corresponding calcium salts is presented. A simple acidic treatment of the calcium salts provides the metal-free Bronsted acids (see scheme; Tf=trifluoromethanesulfonyl).
Synthesis of BINOL derived phosphorodithioic acids as new chiral Br?nsted acids and an improved synthesis of 3,3′-disubstituted H8-BINOL derivatives
Pousse, Guillaume,Devineau, Alice,Dalla, Vincent,Humphreys, Luke,Lasne, Marie-Claire,Rouden, Jacques,Blanchet, Jér?me
body text, p. 10617 - 10622 (2010/01/16)
Original phosphorodithioic acid diesters were prepared according to an improved synthesis of 3,3′-disubstituted H8-BINOL derivatives. In preliminary experiments, these new Br?nsted acids were tested as organocatalysts in three reactions. They promoted the Nazarov cyclisation with mixed selectivities, the Mannich reaction with good enantioselectivity and they catalyzed efficiently the alkylation of N-acyliminium with enol silyl ether.
Iridium-catalyzed hydrogenation of β-dehydroamino acid derivatives using monodentate phosphoramidites
Enthaler, Stephan,Erre, Giulia,Junge, Kathrin,Schroeder, Kristin,Addis, Daniele,Michalik, Dirk,Hapke, Marko,Redkin, Dmitry,Beller, Matthias
scheme or table, p. 3352 - 3362 (2009/04/07)
The iridium-catalyzed asymmetric hydrogenation of 13 different β-dehydroamino acid derivatives to give optically active β-amino acid esters has been examined. Readily accessible monodentate octahydrobinaphthol- based phosphoramidites were used as chiral ligands. Good to excellent enantioselectivities and yields were obtained for the E isomers, whereas poorer catalyst performance was found for the Z isomers. Importantly, to obtain high enantioselectivity, substitution at the 3,3′-positions of the ligands was necessary. Enantioselectivities of up to 94% ee were achieved under optimized conditions. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
A convenient protocol for the synthesis of axially chiral Br?nsted acids
Bartoszek, Michael,Beller, Matthias,Deutsch, Jens,Klawonn, Markus,K?ckritz, Angela,Nemati, Navid,Pews-Davtyan, Anahit
, p. 1316 - 1322 (2008/09/17)
Partially hydrogenated binaphthol monophosphoric acids were prepared via an improved four-step sequence. It is demonstrated that typical protection and deprotection of the phenolic groups are dispensable. The vinyl-substituted derivative has been polymerized to give a novel polymerized organocatalyst.
