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Palladium-Catalyzed C-P Bond-Forming Reactions of Aryl Nonaflates Accelerated by Iodide.

ABSTRACT: An iodide-accelerated, palladium-catalyzed C-P bond-forming reaction of aryl nonaflates is described. The protocol was optimized for the synthesis of aryl phosphine oxides and was found to be tolerant of a wide range of aryl nonaflates. The general nature of this transformation was established with coupling to other P(O)H compounds for the synthesis of aryl phosphonates and an aryl phosphinate. The straightforward synthesis of stable, isolable aryl nonaflates, in combination with the rapid C-P bond-forming reaction allows facile preparation of aryl phosphorus target compounds from readily available phenol starting materials. The synthetic utility of this general strategy was demonstrated with the efficient preparation of an organic light-emitting diode (OLED) material and a phosphonophenylalanine mimic.

SUBMITTER: McErlain H

PROVIDER: S-EPMC8650017 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Recoverable Palladium-Catalyzed Carbon-Carbon Bond Forming Reactions under Thermomorphic Mode: Stille and Suzuki-Miyaura Reactions.

Project description:The reaction of [PdCl2(CH3CN)2] and bis-4,4'-(RfCH2OCH2)-2,2'-bpy (1a-d), where Rf = n-C11F23 (a), n-C10F21 (b), n-C9F19 (c) and n-C8F17 (d), respectively, in the presence of dichloromethane (CH2Cl2) resulted in the synthesis of Pd complex, [PdCl2[4,4'-bis-(RfCH2OCH2)-2,2'-bpy] (2a-d). The Pd-catalyzed Stille arylations of vinyl tributyltin with aryl halides were selected to demonstrate the feasibility of recycling usage with 2a as the catalyst using NMP (N-methyl-2-pyrrolidone) as the solvent at 120-150 °C. Additionally, recycling and electronic effect studies of 2a-c were also carried out for Suzuki-Miyaura reaction of phenylboronic acid derivatives, 4-X-C6H4-B(OH)2, (X = H or Ph) with aryl halide, 4-Y-C6H4-Z, (Y = CN, H or OCH3; Z = I or Br) in dimethylformamide (DMF) at 135-150 °C. At the end of each cycle, the product mixtures were cooled to lower temperature (e.g., -10 °C), and then catalysts were recovered by decantation with Pd leaching less than 1%. The products were quantified by gas chromatography/mass spectrometry (GC/MS) analysis or by the isolated yield. The complex 2a-catalyzed Stille reaction of aryl iodides with vinyl tributyltin have good recycling results for a total of 8 times, with a high yield within short period of time (1-3 h). Similarly, 2a-c-catalyzed Suzuki-Miyaura reactions also have good recycling results. The electronic effect studies from substituents in both Stille and Suzuki-Miyaura coupling reactions showed that electron withdrawing groups speed up the reaction rate. To our knowledge, this is the first example of recoverable fluorous long-chained Pd-catalyzed Stille reactions under the thermomorphic mode.

| S-EPMC7961810 | biostudies-literature

Aryl-CF(3) bond-forming reductive elimination from palladium(IV).

Project description:This communication describes oxidatively induced Ar-CF(3) bond-forming reductive elimination from new Pd(II) complexes of general structure (L approximately L)Pd(II)(Ar)(CF(3)). The electrophilic fluorinating reagent N-fluoro-2,4,6-trimethylpyridinium triflate promotes these reactions in good to excellent yields. The palladium(IV) intermediate ((t)Bu-bpy)Pd(IV)(CF(3))(F)(OTf)(C(6)H(4)F) has been isolated, characterized, and demonstrated to undergo high yielding Ar-CF(3) coupling upon thermolysis. This work provides an attractive conceptual framework for the development of Pd(II/IV)-catalyzed arene trifluoromethylation reactions.

| S-EPMC2832076 | biostudies-literature

Palladium-Catalyzed <i>trans</i>-Hydroalkoxylation: Counterintuitive Use of an Aryl Iodide Additive to Promote C-H Bond Formation.

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Project description:An efficient palladium-catalyzed oxidative C-C bond forming cascade reaction of allenes involving a coupling between an enallene and an allenyne followed by a carbocyclization of the generated Pd-intermediate was developed. This cascade reaction afforded functionalized cross-conjugated polyenes. The enallene is initially activated by palladium and reacts with the allenyne to give the cross-conjugated polyenes.

| S-EPMC7311062 | biostudies-literature

Me3(OMe)tBuXPhos: a surrogate ligand for Me4tBuXPhos in palladium-catalyzed C-N and C-O bond-forming reactions.

Project description:A new biarylphosphine ligand, Me(3)(OMe)tBuXPhos (L3), was designed as a surrogate for Me(4)tBuXPhos (L1). The Me(3)(OMe)tBuXPhos could be prepared in a chromatography-free manner from inexpensive and readily available 2,3,6-trimethylphenol. Comparative studies demonstrated that a catalyst based on Me(3)(OMe)tBuXPhos displayed the same reactivity as a catalyst based on Me(4)tBuXPhos for Pd-catalyzed C-N and C-O bond-forming processes.

| S-EPMC3387921 | biostudies-literature

Palladium- and Nickel-Catalyzed Carbon-Carbon Bond Insertion Reactions with Alkylidenesilacyclopropanes.

Project description:Palladium and nickel catalysts promoted highly selective carbon-carbon bond insertion reactions with di-tert-butyl-alkylidenesilacyclopropanes. Pd(PPh(3))(4) was demonstrated to be the optimal catalyst, allowing for a variety of carbon-carbon pi-bond insertion reactions. Depending on the nature of the carbon-carbon pi bond, the insertion reaction proceeded with either direct insertion into the carbon(sp(2))-silicon bond or with allylic transposition. Ring-substituted alkylidenesilacyclopropanes required a nickel catalyst to afford insertion products. Using Ni(cod)(2) as the carbon-carbon bond insertion catalyst, new double alkyne insertion products and alkene isomerization products were observed.

| S-EPMC2856941 | biostudies-literature

Palladium-Catalyzed Aryl Amination Reactions of 6-Bromo- and 6-Chloropurine Nucleosides.

Project description:Palladium-catalyzed C-N bond forming reactions of 6-bromo- as well as 6-chloropurine ribonucleosides and the 2'-deoxy analogues with aryl amines are described. Efficient conversions were observed with Pd(OAc)(2)/Xantphos/Cs(2)CO(3), in PhMe at 100 °C. Reactions of the bromo nucleoside derivatives could be conducted at a lowered catalytic loading (5 mol % Pd(OAc)(2)/7.5 mol % Xantphos), whereas good product yields were obtained with a higher catalyst load (10 mol % Pd(OAc)(2)/15 mol % Xantphos) when the chloro analogue was employed. Among the examples evaluated, silyl protection for the hydroxyls appears better as compared to acetyl. The methodology has been evaluated via reactions with a variety of aryl amines and by synthesis of biologically relevant deoxyadenosine and adenosine dimers. This is the first detailed analysis of aryl amination reactions of 6-chloropurine nucleosides, and comparison of the two halogenated nucleoside substrates.

| S-EPMC3148652 | biostudies-literature

Enantioselective Aryl-Iodide-Catalyzed Wagner-Meerwein Rearrangements.

Project description:We report a strategy for effecting catalytic, enantioselective carbocationic rearrangements through the intermediacy of alkyl iodanes as stereodefined carbocation equivalents. Asymmetric Wagner-Meerwein rearrangements of β-substituted styrenes are catalyzed by the C2-symmetric aryl iodide 1 to provide access to enantioenriched 1,3-difluorinated molecules possessing interesting and well-defined conformational properties. Hammett and kinetic isotope effect studies, in combination with computational investigations, reveal that two different mechanisms are operative in these rearrangement reactions, with the pathway depending on the identity of the migrating group. In reactions involving alkyl-group migration, intermolecular fluoride attack is product- and enantio-determining. In contrast, reactions in which aryl rearrangement occurs proceed through an enantiodetermining intramolecular 1,2-migration prior to fluorination. The fact that both pathways are promoted by the same chiral aryl iodide catalyst with high enantioselectivity provides a compelling illustration of generality across reaction mechanisms in asymmetric catalysis.

| S-EPMC7523190 | biostudies-literature

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Project description:Treatment of aryl iodides with indium metal in the presence of lithium chloride leads to the formation of an organoindium reagent capable of participating in cross-coupling reactions under transition-metal catalysis. Combination with aryl halides in the presence of 5 mol % Cl2Pd(dppf) furnishes biaryl compounds in good yields; similarly, reaction with acyl halides or allylic acetates/carbonates in the presence of 5-10 mol % palladium catalyst leads to arylketones and allylic substitution products, respectively, in moderate yields. The reactions are tolerant of the presence of protic solvents, and approximately 85% of the indium metal employed can be recovered by reduction of the residual indium salts with zinc(0).

| S-EPMC2548319 | biostudies-literature

Is silver a mere terminal oxidant in palladium catalyzed C-H bond activation reactions?

Project description:In the contemporary practice of palladium catalysis, a molecular understanding of the role of vital additives used in such reactions continues to remain rather vague. Herein, we disclose an intriguing and a potentially general role for one of the most commonly used silver salt additives, discovered through rigorous computational investigations on four diverse Pd-catalyzed C-H bond activation reactions involving sp2 aryl C-H bonds. The catalytic pathways of different reactions such as phosphorylation, arylation, alkynylation, and oxidative cycloaddition are analyzed, with and without the explicit inclusion of the silver additive in the respective transition states and intermediates. Our results indicate that the pivotal role of silver salts is likely to manifest in the form of a Pd-Ag heterobimetallic species that facilitates intermetallic electronic communication. The Pd-Ag interaction is found to provide a consistently lower energetic span as compared to an analogous pathway devoid of such interaction. Identification of a lower energy pathway as well as enhanced catalytic efficiency due to Pd-Ag interaction could have broad practical implications in the mechanism of transition metal catalysis and the current perceptions on the same.

| S-EPMC7012060 | biostudies-literature

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