An Under-Appreciated Source of Reproducibility Issues in Cross-Coupling: Solid-State Decomposition of Primary Sodium Alkoxides in Air

Wethman, Robert; Derosa, Joseph; Kang, Taeho; Apolinar, Omar; Abraham, Anuji; Kleinmans, Roman; Wisniewski, Steven R.; Coombs, John R.; Engle, Keary M.

doi:10.26434/chemrxiv.12818234.v1

Cited by 4 publications

(4 citation statements)

References 1 publication

(2 reference statements)

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“…The sodium alkoxide solutions used throughout this work were prepared by dissolving sodium in the corresponding alcohol, because substantial contamination of commercial batches of sodium alkoxide with sodium carboxylates and sodium carbonate has been reported. 56 While we did not observe any decomposition products of sodium alkoxide batches up to 10 months after preparation by 1 H NMR or 13 C NMR analysis (Figures S2 and S3), potential reproducibility issues arising from degradation of alkoxide batches further motivated the exploration of alternative bases.…”

Section: ■ Extension Of Mof-derived Ru Alloy-catalysis To Other Guerb...mentioning

confidence: 83%

Structural Evolution of MOF-Derived RuCo, A General Catalyst for the Guerbet Reaction

Neumann

Payne

Rozeveld

et al. 2021

ACS Appl. Mater. Interfaces

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Guerbet alcohols, a class of β-branched terminal alcohols, find widespread application because of their low melting points and excellent fluidity. Because of the limitations in the activity and selectivity of existing Guerbet catalysts, Guerbet alcohols are not currently produced via the Guerbet reaction but via hydroformylation of oil-derived alkenes followed by aldol condensation. In pursuit of a one-step synthesis of Guerbet alcohols from simple linear alcohol precursors, we show that MOF-derived RuCo alloys achieve over a million turnovers in the Guerbet reaction of 1-propanol, 1-butanol, and 1-pentanol. The active catalyst is formed in situ from ruthenium-impregnated metal–organic framework MFU-1. XPS and XAS studies indicate that the precatalyst is composed of Ru precursor trapped inside the MOF pores with no change in the oxidation state or coordination environment of Ru upon MOF incorporation. The significantly higher reactivity of Ru-impregnated MOF versus a physical mixture of Ru precursor and MOF suggests that the MOF plays an important role in templating the formation of the active catalyst and/or its stabilization. XPS reveals partial reduction of both ruthenium and MOF-derived cobalt under the Guerbet reaction conditions, and TEM/EDX imaging shows that Ru is decorated on the edges of dense nanoparticles, as well as thin nanoplates of CoO x . The use of ethanol rather than higher alcohols as a substrate results in lower turnover frequencies, and RuCo recovered from ethanol upgrading lacks nanostructures with plate-like morphology and does not exhibit Ru-enrichment on the surface and edge sites. Notably, 1H and 31P NMR studies show that through use of K3PO4 as a base promoter in the RuCo-catalyzed alcohol upgrading, the formation of carboxylate salts, a common side product in the Guerbet reaction, was effectively eliminated.

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Section: ■ Extension Of Mof-derived Ru Alloy-catalysis To Other Guerb...mentioning

confidence: 83%

Structural Evolution of MOF-Derived RuCo, A General Catalyst for the Guerbet Reaction

Neumann

Payne

Rozeveld

et al. 2021

ACS Appl. Mater. Interfaces

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show abstract

“…14 It is notable that similar reaction stalling is observed when potassium tert-amylate is used as a homogeneous base in these reactions (Supporting Information, page S12), and analogous effects have been reported in other publications. 47 It follows that, in general, when a homogeneous, anhydrous Suzuki−Miyaura reaction is conducted in the presence of excess base, the reaction may be significantly inhibited by the saturation of both the palladium complex and boron reagent with base. 4.3.…”

Section: Investigation Of Transmetalation Through Thementioning

confidence: 99%

Potassium Trimethylsilanolate-Promoted, Anhydrous Suzuki–Miyaura Cross-Coupling Reaction Proceeds via the “Boronate Mechanism”: Evidence for the Alternative Fork in the Trail

et al. 2022

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Previous studies have shown that the critical transmetalation step in the Suzuki–Miyaura cross-coupling proceeds through a mechanism wherein an arylpalladium hydroxide complex reacts with an aryl boronic acid, termed the oxo-palladium pathway. Moreover, these same studies have established that the reaction between an aryl boronate and an arylpalladium halide complex (the boronate pathway) is prohibitively slow. Herein, studies on isolated intermediates, along with kinetic analysis, have demonstrated that the Suzuki–Miyaura reaction promoted by potassium trimethylsilanolate (TMSOK) proceeds through the boronate pathway, in contrast with other, established systems. Furthermore, an unprecedented, binuclear palladium(I) complex containing a μ-phenyl bridging ligand was characterized by NMR spectroscopy, mass spectrometry, and computational methods. Density functional theory (DFT) calculations suggest that the binuclear complex exhibits an open-shell ground electronic state, and reaction kinetics implicate the complex in the catalytic cycle. These results expand the breadth of potential mechanisms by which the Suzuki–Miyaura reaction can occur, and the novel binuclear palladium complex discovered has broad implications for palladium-mediated cross-coupling reactions of aryl halides.

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“…We found the addition of NaOMe as a stock solution to be vital for high yields, presumably owing to the slow dissolution rate of the solid base (entry 6). 9 Under our previously published reaction conditions for simple alkenyl amide substrates, the 1,2-diarylated product(s) could be detected in only 8% yield (entry 2). Interestingly, the reaction proceeded in good yield without an ancillary ligand or with 1,3bis(2,6-di-isopropylphenyl)imidazolidine-2-ylidene (SIPr) instead of DMFU, with SIPr leading to lower regioselectivity (entries 4 and 5).…”

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confidence: 91%

Ni-Catalyzed 1,2-Diarylation of Alkenyl Ketones: A Comparative Study of Carbonyl-Directed Reaction Systems

et al. 2021

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A nickel-catalyzed 1,2-diarylation of alkenyl ketones with aryl iodides and arylboronic esters is reported. Ketones with a variety of substituents serve as effective directing groups, offering high levels of regiocontrol. A representative product is diversified into a wide range of useful products that are not readily accessible via existing 1,2-diarylation reactions. Preliminary mechanistic studies shed light on the binding mode of the substrate, and Hammett analysis reveals the effect of electronic factors on initial rates.

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An Under-Appreciated Source of Reproducibility Issues in Cross-Coupling: Solid-State Decomposition of Primary Sodium Alkoxides in Air

Cited by 4 publications

References 1 publication

Structural Evolution of MOF-Derived RuCo, A General Catalyst for the Guerbet Reaction

Structural Evolution of MOF-Derived RuCo, A General Catalyst for the Guerbet Reaction

Potassium Trimethylsilanolate-Promoted, Anhydrous Suzuki–Miyaura Cross-Coupling Reaction Proceeds via the “Boronate Mechanism”: Evidence for the Alternative Fork in the Trail

Ni-Catalyzed 1,2-Diarylation of Alkenyl Ketones: A Comparative Study of Carbonyl-Directed Reaction Systems

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