- Expanding Ligand Space: Preparation, Characterization, and Synthetic Applications of Air-Stable, Odorless Di- tert-alkylphosphine Surrogates
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The di-tert-alkylphosphino motif is common to many best-in-class ligands for late-transition-metal catalysis. However, the structural diversity of these privileged substructures is currently limited by the need to manipulate highly toxic, highly reactive reagents and intermediates in their synthesis. In response to this longstanding challenge, we report an umpolung strategy for the synthesis of structurally diverse di-tert-alkylphosphine building blocks via SN1 alkylation of in situ generated PH3 gas. We show that the products - which are isolated as air-stable, odorless phosphonium salts - can be used directly in the preparation of key synthetic intermediates and ligand classes. The di-tert-alkylphosphino building blocks that are accessible using our methodology therefore enable facile expansion of extant ligand classes by modification of a previously invariant vector; we demonstrate that these modifications affect the steric and electronic properties of the ligands and can be used to tune their performance in catalysis.
- Barber, Thomas,Argent, Stephen P.,Ball, Liam T.
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- Synthesis of L-Au(I)-CF2H Complexes and Their Application as Transmetalation Shuttles to the Difluoromethylation of Aryl Iodides
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We describe herein two alternative protocols to efficiently prepare difluoromethylgold(I) complexes bearing ancillary ligands with different electronic and steric properties. LAu-OX (X = H andt-Bu) species, formed in the presence of base, have been identified as intermediate complexes involved in these transformations. The application of these compounds as “CF2H transmetalation shuttles” from gold to palladium has been demonstrated in a Pd-catalyzed difluoromethylation reaction of aryl iodides, in which the Au-to-Pd transfer of “CF2H” is feasible under stoichiometric conditions. These findings will pave the way for catalytic manifolds in gold chemistry.
- García-Domínguez, Patricia
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p. 2923 - 2928
(2021/09/07)
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- Synthesis, reactivity and catalytic activity of Au-PAd3complexes
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Tri(1-adamantyl)phosphine (PAd3) possesses unique steric and electronic properties positioning it at the border between tertiary phosphines and N-heterocyclic carbenes (NHC). Novel Au-PAd3complexes were synthesized from the known [Au(PAd3)Cl]. We have optimised reaction conditions for the synthesis of this useful synthon in order to circumvent the formation of the [Au(PAd3)2]Cl. [Au(PAd3)Cl] was used to access a number of derivatives and some were deployed as catalysts. The hydration of alkynes was targeted to gauge the reactivity of Au-PAd3complexes and permit comparison with NHC and tertiary phosphine congeners.
- Voloshkin, Vladislav A.,Saab, Marina,Van Hecke, Kristof,Lau, Sii Hong,Carrow, Bradley P.,Nolan, Steven P.
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p. 13872 - 13879
(2020/10/27)
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- Gold(I)-Catalyzed and Nucleophile-Guided Ligand-Directed Divergent Synthesis
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Transition metal catalysts can mediate a plethora of skeleton rearrangements of a range of substrates to construct complex small molecules. Yet, their potential to transform common substrates into distinct molecular scaffolds has not been fully explored to deliver biologically relevant small molecules. Gold(I)-catalyzed transformations of enynes are amongst the most intriguing rearrangements and provide opportunities to access a range of diverse scaffolds efficiently. In ligand-directed divergent synthesis (LDS), variation of ligands in metal complexes determines the fate of substrates during their transformation into distinct scaffolds. For instance, variation of ligands for the gold(I) catalysts helps to transform oxindole derived 1,6-enynes into several distinct molecular frameworks. In this report, we present how ligand variation in gold(I) catalysts, nucleophile-additives and alkyl and alkynyl substitutions on the 1,6-enynes as well as replacement of the oxindole ring with a different privileged ring-system (PRS) influence the LDS approach to access a wider chemical space. Based on the experimental results, we propose several mechanistic pathways in gold(I)-catalyzed cycloisomerizations and cascade reactions of 1,6-enyne substrates leading to structurally distinct chemotypes.
- Lee, Yen-Chun,Knauer, Lena,Louven, Kathrin,Golz, Christopher,Strohmann, Carsten,Waldmann, Herbert,Kumar, Kamal
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supporting information
p. 5688 - 5699
(2018/10/31)
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- Predicting Counterion Effects Using a Gold Affinity Index and a Hydrogen Bonding Basicity Index
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We have developed a gold affinity index and hydrogen bonding basicity index for counterions and have used these indexes to forecast their reactivity in cationic gold catalysis.
- Lu, Zhichao,Han, Junbin,Okoromoba, Otome E.,Shimizu, Naoto,Amii, Hideki,Tormena, Cláudio F.,Hammond, Gerald B.,Xu, Bo
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supporting information
p. 5848 - 5851
(2017/11/10)
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- Building polycyclic indole scaffolds via gold(I)-catalyzed intra- and inter-molecular cyclization reactions of 1,6-enynes
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A gold(I) catalyzed cycloisomerization of indolyl-1,6-enynes via 5-exo-dig cyclization is reported. The reaction passes through an intermediate whose fate can be steered to yield different indole polycyclic scaffolds through various intra- and inter-molecular cyclization reactions. One of the key transformations of indolyl-1,6-enynes was a formal [2+2+2] cycloaddition reaction with various aldehydes to afford natural product-like tetracyclic indoles.
- Pérez-Galán, Patricia,Waldmann, Herbert,Kumar, Kamal
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supporting information
p. 3647 - 3652
(2016/06/06)
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- Synthesis of Substituted Quinolizidines via a Gold-Catalyzed Double Cyclization Cascade
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A novel synthesis of quinolizidines by a cationic gold-catalyzed double cyclization cascade has been developed. The reaction was initiated by the gold-catalyzed 6-exo-dig cyclization of ynamides, which was followed by a second cyclization of an enamide intermediate to provide the corresponding quinolizidine derivatives. The utility of this reaction was demonstrated by application to the synthesis of multi-substituted quinolizidines and by the total synthesis of a quinolizidine alkaloid, (±)-lupinine.
- Nonaka, Shiori,Sugimoto, Kenji,Ueda, Hirofumi,Tokuyama, Hidetoshi
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supporting information
p. 380 - 385
(2016/02/12)
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- Autotandem catalysis: Synthesis of pyrroles by gold-catalyzed cascade reaction
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A novel synthesis of substituted pyrroles by a gold(I)-catalyzed cascade reaction has been developed. The reaction proceeded with an autotandem catalysis consisting of an initial addition of gold-acetylide to an acetal moiety and was followed by gold-catalyzed 5-endo-dig cyclization and aromatization. Gold catalysts play a dual role in activating nucleophilicity or electrophilicity of terminal acetylenes by forming gold-acetylides or by π-coordination. The formal (3 + 2) annulation of two components provided a variety of substituted pyrroles in a modular fashion.
- Ueda, Hirofumi,Yamaguchi, Minami,Kameya, Hiroshi,Sugimoto, Kenji,Tokuyama, Hidetoshi
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supporting information
p. 4948 - 4951
(2015/04/27)
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- Cationic gold catalyst poisoning and reactivation
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High gold affinity impurities (halides, bases) in solvents, starting materials, filtration, or drying agents could affect the reactivity of gold catalyst adversely, which may significantly reduce the TON of cationic gold-catalyzed reactions. Use of a suit
- Kumar, Manish,Hammond, Gerald B.,Xu, Bo
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supporting information
p. 3452 - 3455
(2014/07/21)
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- Gold catalysis: Biarylphosphine ligands as key for the synthesis of dihydroisocoumarins
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Agold-catalyzed phenol synthesis was successfully used in the synthesis of dihydroisocoumarins for the first time.Alarge number of gold(I) complexes were prepared and tested; only complexes based on the biarylphosphine motif were successful. CSIRO 2014.
- Hashmi, A. Stephen K.,Bechem, Benjamin,Loos, Annette,Hamzic, Melissa,Rominger, Frank,Rabaa, Hassan
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p. 481 - 499
(2014/04/03)
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- Leveraging the micellar effect: Gold-catalyzed dehydrative cyclizations in water at room temperature
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The first examples of gold-catalyzed cyclizations of diols and triols to the corresponding hetero- or spirocycles in an aqueous medium are presented. These reactions take place within nanomicelles, where the hydrophobic effect is operating, thereby driving the dehydrations, notwithstanding the surrounding water. By the addition of simple salts such as sodium chloride, reaction times and catalyst loadings can be significantly decreased.
- Minkler, Stefan R. K.,Isley, Nicholas A.,Lippincott, Daniel J.,Krause, Norbert,Lipshutz, Bruce H.
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supporting information
p. 724 - 726
(2014/03/21)
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- Mechanistic study of gold(I)-catalyzed hydroamination of alkynes: Outer or inner sphere mechanism?
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An experimental mechanistic study of the gold(I)-catalyzed hydroamination shows the formation of conformationally flexible auro-iminium salts Au-Im, which originate from the protonation of a vinyl gold species. Rotation around the C-CAu bond is the reason
- Zhdanko, Alexander,Maier, Martin E.
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p. 7760 - 7764
(2014/08/05)
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- A unique Au-Ag-Au triangular motif in a trimetallic halonium dication: Silver incorporation in a gold(I) catalyst
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As a result of explorations into the solution chemistry of silver/gold mixtures, a unique diphosphine trimetallic chloronium dication was discovered that incorporates silver-arene chelation and a triangular mixed gold/silver core in the solid state. Notably, it was isolated from a Celite prefiltered solution initially thought to be silver-free. The crystal structure also incorporates the coordination to silver of one fluorine atom of one SbF6 - counterion. The structure was compared to two new, but well-precedented, phosphine digold chloride cations. DFT calculations supported significant silver-halide and silver-arene interactions in the mixed gold/silver complex and metallophilic interactions in all three complexes. Comparison of computed data revealed that the ωB97X-D functional, which has a long-range corrected hybrid with atom-atom dispersion corrections, gave a better fit to the experimental data compared with the PBE0 functional, which has previously failed to capture aurophilic interactions. Preliminary studies support the presence of the mixed gold/silver structure in solution. Silver lining! As a result of explorations into the solution chemistry of silver/gold mixtures, a unique trimetallic chloronium dication was discovered that incorporates silver-arene chelation and a triangular mixed gold/silver core (see figure). Notably, it was isolated from a previously Celite-filtered solution, a procedure generally believed to be efficient at removing silver. The solid-state and solution structure, as well as DFT calculations are reported herein. Copyright
- Zhu, Yuyang,Day, Cynthia S.,Zhang, Lin,Hauser, Katarina J.,Jones, Amanda C.
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supporting information
p. 12264 - 12271
(2013/09/23)
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- Efficient general procedure to access a diversity of gold(0) particles and gold(I) phosphine complexes from a simple HAuCl4 source. Localization of homogeneous/heterogeneous system's interface and field-emission scanning electron microscopy study
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Soluble gold precatalysts, aimed for homogeneous catalysis, under certain conditions may form nanoparticles, which dramatically change the mechanism and initiate different chemistry. The present study addresses the question of designing gold catalysts, taking into account possible interconversions and contamination at the homogeneous/heterogeneous system's interface. It was revealed that accurate localization of boundary experimental conditions for formation of molecular gold complexes in solution versus nucleation and growth of gold particles opens new opportunities for well-known gold chemistry. Within the developed concept, a series of practical procedures was created for efficient synthesis of soluble gold complexes with various phosphine ligands (R3P)AuCl (90-99% yield) and for preparation of different types of gold materials. The effect of the ligand on the particles growth in solution has been observed and characterized with high-resolution field-emission scanning electron microscopy (FE-SEM) study. Two unique types of nanostructured gold materials were prepared: hierarchical agglomerates and gold mirror composed of ultrafine smoothly shaped particles.
- Zalesskiy, Sergey S.,Sedykh, Alexander E.,Kashin, Alexey S.,Ananikov, Valentine P.
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supporting information
p. 3550 - 3559
(2013/05/09)
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