A mechanistic investigation into the elimination of phosphonium salts from rhodium–TRIPHOS complexes under methanol carbonylation conditions

When arylmethyl phosphonium salts are treated with a base (e.g., t-BuOK or NaH) they homocouple to form symmetric 1,2-diarylethenes. In some cases, dilution and (or) use of excess base lead to very high yields of the product. This reaction is solvent sensitive: the reaction occurs only when polar aprotic solvents such as acetonitrile or DMSO are used. Other alkyl phosphonium salts (e.g., ethoxycarbonylmethyltriphenylphosphonium bromide and n-butyltriphenylphosphonium bromide) form a ylid (when an α-carbonyl group is present) or lose a phenyl group to form alkyldiphenylphosphine oxides when treated with the base. Mechanistic investigation of the homocoupling reaction indicates that the reaction proceeds through a ylid that acts as a nucleophile on an unreacted phosphonium salt. The resulting adduct undergoes elimination to form the observed product. The E/Z ratio seems to depend on the amount of the base used and the phosphonium salt involved.Key words: phosphonium salts, homocoupling, 1,2-diarylalkene, Ylids.

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Kinetics and mechanistic investigation of epoxy-anhydride compositions cured with quaternary phosphonium salts as accelerators

Journal of Polymer Science Part A Polymer Chemistry ◽

10.1002/pola.27946 ◽

2015 ◽

Vol 54 (8) ◽

pp. 1088-1097 ◽

Cited By ~ 7

Author(s):

Lyaysan R. Amirova ◽

Alexander R. Burilov ◽

Liliya M. Amirova ◽

Ingmar Bauer ◽

Wolf D. Habicher

Keyword(s):

Phosphonium Salts ◽

Mechanistic Investigation ◽

Quaternary Phosphonium Salts

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Evolution of Metastable Structures in Bimetallic Catalysts from Microscopy and Machine-Learning Molecular Dynamics

10.26434/chemrxiv.11811660.v1 ◽

2020 ◽

Author(s):

Jin Soo Lim ◽

Jonathan Vandermause ◽

Matthijs A. van Spronsen ◽

Albert Musaelian ◽

Christopher R. O’Connor ◽

...

Keyword(s):

Machine Learning ◽

Molecular Dynamics ◽

Large Scale ◽

Materials Science ◽

Complete Characterization ◽

Layer By Layer ◽

Surface Restructuring ◽

Metastable Structures ◽

Mechanistic Investigation ◽

Underlying Mechanisms

Restructuring of interface plays a crucial role in materials science and heterogeneous catalysis. Bimetallic systems, in particular, often adopt very different composition and morphology at surfaces compared to the bulk. For the first time, we reveal a detailed atomistic picture of the long-timescale restructuring of Pd deposited on Ag, using microscopy, spectroscopy, and novel simulation methods. Encapsulation of Pd by Ag always precedes layer-by-layer dissolution of Pd, resulting in significant Ag migration out of the surface and extensive vacancy pits. These metastable structures are of vital catalytic importance, as Ag-encapsulated Pd remains much more accessible to reactants than bulk-dissolved Pd. The underlying mechanisms are uncovered by performing fast and large-scale machine-learning molecular dynamics, followed by our newly developed method for complete characterization of atomic surface restructuring events. Our approach is broadly applicable to other multimetallic systems of interest and enables the previously impractical mechanistic investigation of restructuring dynamics.

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Theoretical and experimental studies of palladium-catalyzed site-selective C(sp3)−H bond functionalization enabled by transient ligands

10.26434/chemrxiv.5717950 ◽

2017 ◽

Author(s):

Haibo Ge ◽

Lei Pan ◽

Piaoping Tang ◽

Ke Yang ◽

Mian Wang ◽

...

Keyword(s):

Bond Activation ◽

Theoretical Calculations ◽

Experimental Studies ◽

Bond Functionalization ◽

Aliphatic Ketones ◽

Site Selectivity ◽

Mechanistic Investigation ◽

Palladium Catalyzed ◽

Metal Catalyzed ◽

Site Selective

Transition metal-catalyzed selective C–H bond functionalization enabled by transient ligands has become an extremely attractive topic due to its economical and greener characteristics. However, catalytic pathways of this reaction process on unactivated sp3 carbons of reactants have not been well studied yet. Herein, detailed mechanistic investigation on Pd-catalyzed C(sp3)–H bond activation with amino acids as transient ligands has been systematically conducted. The theoretical calculations showed that higher angle distortion of C(sp2)-H bond over C(sp3)-H bond and stronger nucleophilicity of benzylic anion over its aromatic counterpart, leading to higher reactivity of corresponding C(sp3)–H bonds; the angle strain of the directing rings of key intermediates determines the site-selectivity of aliphatic ketone substrates; replacement of glycine with β-alanine as the transient ligand can decrease the angle tension of the directing rings. Synthetic experiments have confirmed that β-alanine is indeed a more efficient transient ligand for arylation of β-secondary carbons of linear aliphatic ketones than its glycine counterpart.

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Mechanistic Investigation of Rh(I)-Catalyzed Asymmetric Suzuki-Miyaura Coupling with Racemic Allyl Halides

10.26434/chemrxiv.8208617.v1 ◽

2019 ◽

Cited By ~ 2

Author(s):

Lucy van Dijk ◽

Ruchuta Ardkhean ◽

Mireia Sidera ◽

Sedef Karabiyikoglu ◽

Özlem Sari ◽

...

Keyword(s):

Quantum Chemical Calculations ◽

Quantum Chemical ◽

Experimental Studies ◽

Mechanistic Investigation ◽

Allyl Halides

A mechanism for Rh(I)-catalyzed asymmetric Suzuki-Miyaura coupling with racemic allyl halides is proposed based on a combination of experimental studies and quantum chemical calculations.

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α-Alkoxyalkyl Triphenylphosphonium Salts: Synthesis and Reactions

Current Organic Chemistry ◽

10.2174/1385272823666190926092242 ◽

2019 ◽

Vol 23 (16) ◽

pp. 1738-1755

Author(s):

Humaira Y. Gondal ◽

Zain M. Cheema ◽

Abdul R. Raza ◽

Ahmed Abbaskhan ◽

M. I. Chaudhary

Keyword(s):

Carbonyl Compounds ◽

Claisen Rearrangement ◽

Alder Reaction ◽

Coupling Reactions ◽

Phosphonium Salts ◽

Organic Transformations ◽

Enol Ethers ◽

Wide Range ◽

Synthetic Methodologies ◽

Alkoxy Groups

Following numerous applications of Wittig reaction now functionalized phosphonium salts are gaining attention due to their characteristic properties and diverse reactivity. This review is focused on α-alkoxyalkyl triphenylphosphonium salts: an important class of functionalized phosphonium salts. Alkoxymethyltriphenylphosphonium salts are majorly employed in the carbon homologation of carbonyl compounds and preparation of enol ethers. Their methylene insertion strategy is extensively demonstrated in the total synthesis of a wide range of natural products and other important organic molecules. Similarly enol ethers prepared thereof are important precursors for different organic transformations like Diels-Alder reaction, Claisen rearrangement, Coupling reactions, Olefin metathesis and Nazarov cyclization. Reactivity of these α-alkoxyalkylphosphonium salts have also been studied in the nucleophilic substitution reactions. A distinctive application of this class of phosphonium salts was recently reported in the phenylation of carbonyl compounds under very mild conditions. Synthesis of structurally diverse alkoxymethyltriphenylphosphonium salts with variation in alkoxy groups as well as counter anions are reported in literature. Here we present a detailed account of different synthetic methodologies for the preparation of this unique class of quaternary phosphonium salts and their applications in organic synthesis.

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