General Method for Quantitation of Organic Hydroperoxides

Beutner, Gregory L.; Ayers, Sloan; Chen, Tao; Leung, Simon; Tai, Hua Chia; Wang, Qinggang

doi:10.1021/acs.oprd.0c00251

Cited by 11 publications

(13 citation statements)

References 30 publications

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“…Further quantitative NMR analysis revealed that there was 1458 ppm of peroxide in the old bottle of NMP, while no detectable level of the peroxide was detected in the new bottle . The amount of peroxide in the old bottle of NMP would translate to ∼1.8 equiv relative to Pd, which is sufficient to oxidize all the DPPBz ligand in the Heck reaction.…”

Section: Resultsmentioning

confidence: 98%

Development of a Chromane-Forming Heck Reaction: Bisphosphine Mono-Oxide Mediated Regioselectivity Perturbed by Solvent-Based Peroxide Formation

Doggett

Hay

McKenna

et al. 2023

Org. Process Res. Dev.

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The development of an exocyclic-selective, chromane-forming Heck reaction is reported. Detailed mechanistic studies revealed the crucial role of a bisphosphine mono-oxide-based Pd complex to promote high exo:endo alkene selectivity (>99:1) in the Heck reaction. Low levels of NMP peroxide in NMP (reaction solvent) can impact this selectivity by overoxidizing the ligand to bisphosphineoxide and promoting catalyst decomposition. The resultant colloidal Pd facilitates isomerization leading to significant levels of the undesired endocyclic alkene (>10%). A second-generation process is therefore developed to mitigate the risk of peroxides in NMP.

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Section: Resultsmentioning

confidence: 98%

Development of a Chromane-Forming Heck Reaction: Bisphosphine Mono-Oxide Mediated Regioselectivity Perturbed by Solvent-Based Peroxide Formation

Doggett

Hay

McKenna

et al. 2023

Org. Process Res. Dev.

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“…We hypothesize that the inhibitor prevents yield variability by maintaining low peroxide levels in the solvent during long-term storage. [28] Entries 1-4 in Scheme 4C.2 demon-Scheme 3. Substrate scope.…”

Section: Methodsmentioning

confidence: 99%

Electroreductive Synthesis of Nickel(0) Complexes**

Rubel,

Cao,

El‐Hayek Ewing

et al. 2023

Angew Chem Int Ed

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Over the last fifty years, the use of nickel catalysts for facilitating organic transformations has skyrocketed. Nickel(0) sources act as useful precatalysts because they can enter a catalytic cycle through ligand exchange, without needing to undergo additional elementary steps. However, most Ni(0) precatalysts are synthesized with stoichiometric aluminum–hydride reductants, pyrophoric reagents that are not atom‐economical and must be used at cryogenic temperatures. Here, we demonstrate that Ni(II) salts can be reduced on preparative scale using electrolysis to yield a variety of Ni(0) and Ni(II) complexes that are widely used as precatalysts in organic synthesis, including bis(1,5‐cyclooctadiene)nickel(0) [Ni(COD)2]. This method overcomes the reproducibility issues of previously reported methods by standardizing the procedure, such that it can be performed anywhere in a robust manner. It can be transitioned to large scale through an electrochemical recirculating flow process and extended to an in situ reduction protocol to generate catalytic amounts of Ni(0) for organic transformations. We anticipate that this work will accelerate adoption of preparative electrochemistry for the synthesis of low‐valent organometallic complexes in academia and industry.

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“…Based on the aforementioned report by Morandi and coworkers, we wondered whether the BHT was acting to stabilize the Ni(I) intermediate or whether the reaction was sensitive to peroxides, in which case the inhibitor would likely serve to maintain low peroxide levels in the solvent during long-term storage. [27] A series of tests ruled out the former hypothesis, suggesting that radicals from solvent are indeed detrimental to the electrochemical synthesis of Ni(COD)2, possibly due to passivation of the electrodes. Thus, variation in yield between BHT-free THF bottles was attributed to variation in peroxide content.…”

Section: Nimentioning

confidence: 99%

Electroreductive Synthesis of Nickel(0) Complexes

Rubel

Yi-lin

Ewing

et al. 2023

Preprint

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Over the last fifty years, the use of nickel catalysts for facilitating organic transformations has skyrocketed. Ni(0) sources act as useful precatalysts because they can enter a catalytic cycle through ligand exchange, without needing to undergo additional elementary steps. However, most Ni(0) precatalysts are synthesized with stoichiometric aluminum–hydride reductants, pyrophoric reagents that are not atom-economical and must be used at cryogenic temperatures. Here, we demonstrate that Ni(II) salts can be reduced on preparative scale using electrolysis to yield a variety of Ni(0) and Ni(II) complexes that are widely used as precatalysts in organic synthesis, including bis(1,5-cyclooctadiene)nickel(0) [Ni(COD)2]. This method overcomes the reproducibility issues of previously reported methods by standardizing the procedure, such that it can be performed anywhere in a robust manner. It can be easily transitioned to large scale through an electrochemical recirculating flow process. We anticipate that this work will accelerate adoption of preparative electrochemistry for the synthesis of low-valent organometallic complexes in academia and industry.

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General Method for Quantitation of Organic Hydroperoxides

Cited by 11 publications

References 30 publications

Development of a Chromane-Forming Heck Reaction: Bisphosphine Mono-Oxide Mediated Regioselectivity Perturbed by Solvent-Based Peroxide Formation

Development of a Chromane-Forming Heck Reaction: Bisphosphine Mono-Oxide Mediated Regioselectivity Perturbed by Solvent-Based Peroxide Formation

Electroreductive Synthesis of Nickel(0) Complexes**

Electroreductive Synthesis of Nickel(0) Complexes

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