Reaction kinetics of a water-soluble palladium-β-cyclodextrin catalyst for a Suzuki-Miyaura cross-coupling in continuous flow

Yukun Liu, Ryan Hartman

Research output: Contribution to journalArticle

Abstract

In the present study, a capillary microreactor experiment was designed to study the kinetics of a sample Suzuki-Miyaura coupling using a water-soluble Pd-β-cyclodextrin (Pd-β-CD) catalyst. A water-ethanol solvent system was explored as a potential reaction medium for easy separation of organic species and the metal catalyst, as well as fluid delivery in a continuous microfluidic system. The biphasic, liquid-liquid cross-coupling using the natural product as a ligand was examined for the first time in continuous flow. Mass transfer limitations were concluded to be negligible by estimation of the Hatta number ≪0.02. A catalytic cycle with a third order oxidative addition step was proposed and verified by measurement of the kinetics at different temperatures and residence times. The oxidative addition step was discovered to be the rate determining step, while the activation energy was determined to be 50.1 ± 4.7 kJ mol-1, or less than previously reported values of the free energy barrier of the oxidative addition transition state in the range of 60 to 113 kJ mol-1. A possible explanation is the dual site catalyst design, which may cooperate to lower the free energy barrier. The use of natural products as ligands for the Suzuki-Miyaura coupling has the potential to advance green chemistry and manufacturing of useful fine chemicals, materials, natural products, and pharmaceuticals.

Original languageEnglish (US)
Pages (from-to)1341-1346
Number of pages6
JournalReaction Chemistry and Engineering
Volume4
Issue number7
DOIs
StatePublished - Jul 1 2019

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Cyclodextrins
Palladium
Biological Products
Reaction kinetics
Energy barriers
Catalysts
Free energy
Water
Ligands
Kinetics
Liquids
Microfluidics
Drug products
Ethanol
Mass transfer
Activation energy
Metals
Fluids
Pharmaceutical Preparations
Experiments

ASJC Scopus subject areas

  • Catalysis
  • Chemistry (miscellaneous)
  • Chemical Engineering (miscellaneous)
  • Process Chemistry and Technology
  • Fluid Flow and Transfer Processes

Cite this

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abstract = "In the present study, a capillary microreactor experiment was designed to study the kinetics of a sample Suzuki-Miyaura coupling using a water-soluble Pd-β-cyclodextrin (Pd-β-CD) catalyst. A water-ethanol solvent system was explored as a potential reaction medium for easy separation of organic species and the metal catalyst, as well as fluid delivery in a continuous microfluidic system. The biphasic, liquid-liquid cross-coupling using the natural product as a ligand was examined for the first time in continuous flow. Mass transfer limitations were concluded to be negligible by estimation of the Hatta number ≪0.02. A catalytic cycle with a third order oxidative addition step was proposed and verified by measurement of the kinetics at different temperatures and residence times. The oxidative addition step was discovered to be the rate determining step, while the activation energy was determined to be 50.1 ± 4.7 kJ mol-1, or less than previously reported values of the free energy barrier of the oxidative addition transition state in the range of 60 to 113 kJ mol-1. A possible explanation is the dual site catalyst design, which may cooperate to lower the free energy barrier. The use of natural products as ligands for the Suzuki-Miyaura coupling has the potential to advance green chemistry and manufacturing of useful fine chemicals, materials, natural products, and pharmaceuticals.",
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