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Zinc and manganese are widely used as reductants in synthetic methods, such as nickel-catalyzed cross-electrophile coupling (XEC) reactions, but their redox potentials are unknown in organic solvents. Here, we show how open-circuit potential measurements may be used to determine the thermodynamic potentials of Zn and Mn in different organic solvents and in the presence of common reaction additives. The impact of these Zn and Mn potentials is analyzed for a pair of Ni-catalyzed reactions, each showing a preference for one of the two reductants. Ni-catalyzed coupling of N-alkyl-2,4,6-triphenylpyridinium reagents (Katritzky salts) with aryl halides are then compared under chemical reaction conditions, using Zn or Mn reductants, and under electrochemical conditions performed at applied potentials corresponding to the Zn and Mn reduction potentials and at potentials optimized to achieve the maximum yield. The collective results illuminate the important role of reductant redox potential in Ni-catalyzed XEC reactions.
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Glass surface as strong base, ‘green’ heterogeneous catalyst and degradation reagent
Systematic screening of accelerated chemical reactions at solid/solution interfaces has been carried out in high-throughput fashion using desorption electrospray ionization mass spectrometry and it provides evidence that glass surfaces accelerate various base-catalyzed chemical reactions. The reaction types include elimination, solvolysis, condensation and oxidation, whether or not the substrates are pre-charged. In a detailed mechanistic study, we provide evidence using nanoESI showing that glass surfaces can act as strong bases and convert protic solvents into their conjugate bases which then act as bases/nucleophiles when participating in chemical reactions. In aprotic solvents such as acetonitrile, glass surfaces act as ‘green’ heterogeneous catalysts that can be recovered and reused after simple rinsing. Besides their use in organic reaction catalysis, glass surfaces are also found to act as degradation reagents for phospholipids with increasing extents of degradation occurring at low concentrations. This finding suggests that the storage of base/nucleophile-labile compounds or lipids in glass containers should be avoided.
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- Award ID(s):
- 1905087
- PAR ID:
- 10333763
- Date Published:
- Journal Name:
- Chemical Science
- Volume:
- 12
- Issue:
- 28
- ISSN:
- 2041-6520
- Page Range / eLocation ID:
- 9816 to 9822
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D1SC02708E
