69209-32-1Relevant academic research and scientific papers
Versatile Visible-Light-Driven Synthesis of Asymmetrical Phosphines and Phosphonium Salts
Arockiam, Percia Beatrice,Lennert, Ulrich,Graf, Christina,Rothfelder, Robin,Scott, Daniel J.,Fischer, Tillmann G.,Zeitler, Kirsten,Wolf, Robert
, p. 16374 - 16382 (2020)
Asymmetrically substituted tertiary phosphines and quaternary phosphonium salts are used extensively in applications throughout industry and academia. Despite their significance, classical methods to synthesize such compounds often demand either harsh reaction conditions, prefunctionalization of starting materials, highly sensitive organometallic reagents, or expensive transition-metal catalysts. Mild, practical methods thus remain elusive, despite being of great current interest. Herein, we describe a visible-light-driven method to form these products from secondary and primary phosphines. Using an inexpensive organic photocatalyst and blue-light irradiation, arylphosphines can be both alkylated and arylated using commercially available organohalides. In addition, the same organocatalyst can be used to transform white phosphorus (P4) directly into symmetrical aryl phosphines and phosphonium salts in a single reaction step, which has previously only been possible using precious metal catalysis.
Transition-state stabilization by a secondary substrate-ligand interaction: A new design principle for highly efficient transition-metal catalysis
Smejkal, Tomas,Gribkov, Denis,Geier, Jens,Keller, Manfred,Breit, Bernhard
supporting information; experimental part, p. 2470 - 2478 (2010/06/17)
A library of monodentate phosphane ligands, each bearing a guanidine receptor unit for carboxylates, was designed. Screening of the library gave some excellent catalysts for regioselective hydroformylation of ss,γ- unsaturated carboxylic acids. A terminal alkene, but-3-enoic acid, was hydroformylated with a linear/branched (l/b) regioselectivity up to 41. An internal alkene, pent-3-enoic acid was hydroformylated with regioselectivity up to 18:1. Further substrate selectivity (e.g., acid vs. methyl ester) and reaction site selectivity (monofunctionalization of 2- vinylhept-2-enoic acid) were also achieved. Exploration of the structure-activity relationship and a practical and theoretical mechanistic study gave us an insight into the nature of the supramolecular guanidinium-carboxylate interaction within the catalytic system. This allowed us to identify a selective transition-state stabilization by a secondary substrate-ligand interaction as the basis for catalyst activity and selectivity.
Cooperative effect of a classical and a weak hydrogen bond for the metalInduced construction of a self-assembled β-turn mimic
Laungani, Andy C.,Keller, Manfred,Slattery, John M.,Krossing, Ingo,Breit, Bernhard
experimental part, p. 10405 - 10422 (2010/04/05)
A novel metal-induced template for the self-assembly of two independent phosphane ligands by means of unprecedented multiple noncovalent interactions (classical hydrogen bond, weak hydrogen bond, metal coordination, π-stacking interaction) was developed and investigated. Our results address the importance and capability of weak hydrogen bonds (WHBs) as important attractive interactions in selfassembling processes based on molecular recognition. Together with a classical hydrogen bond, WHBs may serve as promoters for the specific self-assembly of complementary monomeric phosphane ligands into supramolecular hybrid structures. The formation of an intermolecular C-H...N hydrogen bond and its persistence in the solid state and in solution was studied by X-ray crystal analysis, mass spectrometry and NMR spectroscopy analysis. Further evidence was demonstrated by DFT calculations, which gave specific geometric parameters for the proposed conformations and allowed us to estimate the energy involved in the hydrogen bonds that are responsible for the molecular recognition process. The presented template can be regarded as a new type of self-assembled β-turn mimic or supramolecular pseudo amino acid for the nucleation of β-sheet structures when attached to oligopeptides.
Supramolecular bidentate ligands by metal-directed in situ formation of antiparallel β-sheet structures and application in asymmetric catalysis
Laungani, Andy C.,Slattery, John M.,Krossing, Ingo,Breit, Bernhard
experimental part, p. 4488 - 4502 (2009/05/07)
The principles of protein structure design, molecular recognition, and supramolecular and combinatorial chemistry have been applied to develop a convergent metal-ion-assisted self-assembly approach that is a very simple and effective method for the de novo design and the construction of topologically predetermined antiparallel β-sheet structures and self-assembled catalysts. A new concept of in situ generation of bidentate P-ligands for transition-metal catalysis, in which two complementary, monodentate, peptide-based ligands are brought together by employing peptide secondary structure motif as constructing tool to direct the self-assembly process, is achieved through formation of stable β-sheet motifs and subsequent control of selectivity. The supramolecular structures were studied by 1H, 31P, and 13C NMR spectroscopy, ESI mass spectrometry, X-ray structure analysis, and theoretical calculations. Our initial catalysis results confirm the close relationship between the self-assembled sheet conformations and the catalytic activity of these metallopeptides in the asymmetric rhodium-catalyzed hydroformylation. Good catalyst activity and moderate enantioselectivity were observed for the selected combination of catalyst and substrate, but most importantly the concept of this new methodology was successfully proven. This work presents a perspective interface between protein design and supramolecular catalysis for the design of β-sheet mimetics and screening of libraries of self-organizing supramolecular catalysts.
